Studies on arbuscular mycorrhiza (AM) in the Alentejo (Portugal) using pea mutants resistant to AM fungi as a control tool for field conditions

The utilization and management of arbuscular mycorrhiza (AM) symbiosis may improve production and sustainability of the cropping system. For this purpose, native AM fungi (AMF) were sought and tested for their efficiency to increase plant growth by enhanced P uptake and by alleviation of drought stress. Pot experiments with safflower (Carthamus tinctorius) and pea (Pisum sativum) in five soils (mostly sandy loamy Luvisols) and field experiments with peas were carried out during three years at four different sites. Host plants were grown in heated soils inoculated with AMF or the respective heat sterilized inoculum. In the case of peas, mutants resistant to AMF colonization were used as non-mycorrhizal controls. The mycorrhizal impact on yields and its components, transpiration, and P and N uptake was studied in several experiments, partly under varying P and N levels and water supply. Screening of native AMF by most probable number bioassays was not very meaningful. Soil monoliths were placed in the open to simulate field conditions. Inoculation with a native AMF mix improved grain yield, shoot and leaf growth variables as compared to control. Exposed to drought, higher soil water depletion of mycorrhizal plants resulted in a haying-off effect. The growth response to this inoculum could not be significantly reproduced in a subsequent open air pot experiment at two levels of irrigation and P fertilization, however, safflower grew better at higher P and water supply by multiples. The water use efficiency concerning biomass was improved by the AMF inoculum in the two experiments. Transpiration rates were not significantly affected by AM but as a tendency were higher in non-mycorrhizal safflower. A fundamental methodological problem in mycorrhiza field research is providing an appropriate (negative) control for the experimental factor arbuscular mycorrhiza. Soil sterilization or fungicide treatment have undesirable side effects in field and greenhouse settings. Furthermore, artificial rooting, temperature and light conditions in pot experiments may interfere with the interpretation of mycorrhiza effects. Therefore, the myc- pea mutant P2 was tested as a non-mycorrhizal control in a bioassay to evaluate AMF under field conditions in comparison to the symbiotic isogenetic wild type of var. FRISSON as a new integrative approach. However, mutant P2 is also of nod- phenotype and therefore unable to fix N2. A 3-factorial experiment was carried out in a climate chamber at high NPK fertilization to examine the two isolines under non-symbiotic and symbiotic conditions. P2 achieved the same (or higher) biomass as wild type both under good and poor water supply. However, inoculation with the AMF Glomus manihot did not improve plant growth. Differences of grain and straw yields in field trials were large (up to 80 per cent) between those isogenetic pea lines mainly due to higher P uptake under P and water limited conditions. The lacking N2 fixation in mutants was compensated for by high mineral N supply as indicated by the high N status of the pea mutant plants. This finding was corroborated by the results of a major field experiment at three sites with two levels of N fertilization. The higher N rate did not affect grain or straw yields of the non-fixing mutants. Very efficient AMF were detected in a Ferric Luvisol on pasture land as revealed by yield levels of the evaluation crop and by functional vital staining of highly colonized roots. Generally, levels of grain yield were low, at between 40 and 980 kg ha-1. An additional pot trial was carried out to elucidate the strong mycorrhizal effect in the Ferric Luvisol. A triplication of the plant equivalent field P fertilization was necessary to compensate for the mycorrhizal benefit which was with five times higher grain yield very similar to that found in the field experiment. However, the yield differences between the two isolines were not always plausible as the evaluation variable because they were also found in (small) field test trials with apparently sufficient P and N supply and in a soil of almost no AMF potential. This similarly occurred for pea lines of var. SPARKLE and its non-fixing mycorrhizal (E135) and non-symbiotic (R25) isomutants, which were tested in order to exclude experimentally undesirable benefits by N2 fixation. In contrast to var. FRISSON, SPARKLE was not a suitable variety for Mediterranean field conditions. This raises suspicion putative genetic defects other than symbiotic ones may be effective under field conditions, which would conflict with the concept of an appropriate control. It was concluded that AMF resistant plants may help to overcome fundamental problems of present research on arbuscular mycorrhiza, but may create new ones.

Low-altitude aerial photography for optimum N fertilization of winter wheat on the North China Plain

Previous research has shown that site-specific nitrogen (N) fertilizer recommendations based on an assessment of a soil���s N supply (mineral N testing) and the crop���s N status (sap nitrate analysis) can help to decrease excessive N inputs for winter wheat on the North China Plain. However, the costs to derive such recommendations based on multiple sampling of a single field hamper the use of this approach at the on-farm level. In this study low-altitude aerial true-color photographs were used to examine the relationship between image-derived reflectance values and soil���plant data in an on-station experiment. Treatments comprised a conventional N treatment (typical farmers��� practice), an optimum N treatment (N application based on soil���plant testing) and six treatments without N (one to six cropping seasons without any N fertilizer input). Normalized intensities of the red, green and blue color bands on the photographs were highly correlated with total N concentrations, SPAD readings and stem sap nitrate of winter wheat. The results indicate the potential of aerial photography to determine in combination with on site soil���plant testing the optimum N fertilizer rate for larger fields and to thereby decrease the costs for N need assessments.

Modelling of global crop production and resulting N2O emissions

Landwirtschaft spielt eine zentrale Rolle im Erdsystem. Sie tr��gt durch die Emission von CO2, CH4 und N2O zum Treibhauseffekt bei, kann Bodendegradation und Eutrophierung verursachen, regionale Wasserkreisl��ufe ver��ndern und wird au��erdem stark vom Klimawandel betroffen sein. Da all diese Prozesse durch die zugrunde liegenden N��hrstoff- und Wasserfl��sse eng miteinander verkn��pft sind, sollten sie in einem konsistenten Modellansatz betrachtet werden. Dennoch haben Datenmangel und ungen��gendes Prozessverst��ndnis dies bis vor kurzem auf der globalen Skala verhindert. In dieser Arbeit wird die erste Version eines solchen konsistenten globalen Modellansatzes pr��sentiert, wobei der Schwerpunkt auf der Simulation landwirtschaftlicher Ertr��ge und den resultierenden N2O-Emissionen liegt. Der Grund f��r diese Schwerpunktsetzung liegt darin, dass die korrekte Abbildung des Pflanzenwachstums eine essentielle Voraussetzung f��r die Simulation aller anderen Prozesse ist. Des weiteren sind aktuelle und potentielle landwirtschaftliche Ertr��ge wichtige treibende Kr��fte f��r Landnutzungs��nderungen und werden stark vom Klimawandel betroffen sein. Den zweiten Schwerpunkt bildet die Absch��tzung landwirtschaftlicher N2O-Emissionen, da bislang kein prozessbasiertes N2O-Modell auf der globalen Skala eingesetzt wurde. Als Grundlage f��r die globale Modellierung wurde das bestehende Agrar��kosystemmodell Daycent gew��hlt. Neben der Schaffung der Simulationsumgebung wurden zun��chst die ben��tigten globalen Datens��tze f��r Bodenparameter, Klima und landwirtschaftliche Bewirtschaftung zusammengestellt. Da f��r Pflanzzeitpunkte bislang keine globale Datenbasis zur Verf��gung steht, und diese sich mit dem Klimawandel ��ndern werden, wurde eine Routine zur Berechnung von Pflanzzeitpunkten entwickelt. Die Ergebnisse zeigen eine gute ��bereinstimmung mit Anbaukalendern der FAO, die f��r einige Feldfr��chte und L��nder verf��gbar sind. Danach wurde das Daycent-Modell f��r die Ertragsberechnung von Weizen, Reis, Mais, Soja, Hirse, H��lsenfr��chten, Kartoffel, Cassava und Baumwolle parametrisiert und kalibriert. Die Simulationsergebnisse zeigen, dass Daycent die wichtigsten Klima-, Boden- und Bewirtschaftungseffekte auf die Ertragsbildung korrekt abbildet. Berechnete L��nderdurchschnitte stimmen gut mit Daten der FAO ��berein (R2 = 0.66 f��r Weizen, Reis und Mais; R2 = 0.32 f��r Soja), und r��umliche Ertragsmuster entsprechen weitgehend der beobachteten Verteilung von Feldfr��chten und subnationalen Statistiken. Vor der Modellierung landwirtschaftlicher N2O-Emissionen mit dem Daycent-Modell stand eine statistische Analyse von N2O-und NO-Emissionsmessungen aus nat��rlichen und landwirtschaftlichen ��kosystemen. Die als signifikant identifizierten Parameter f��r N2O (D��ngemenge, Bodenkohlenstoffgehalt, Boden-pH, Textur, Feldfrucht, D��ngersorte) und NO (D��ngemenge, Bodenstickstoffgehalt, Klima) entsprechen weitgehend den Ergebnissen einer fr��heren Analyse. F��r Emissionen aus B��den unter nat��rlicher Vegetation, f��r die es bislang keine solche statistische Untersuchung gab, haben Bodenkohlenstoffgehalt, Boden-pH, Lagerungsdichte, Drainierung und Vegetationstyp einen signifikanten Einfluss auf die N2O-Emissionen, w��hrend NO-Emissionen signifikant von Bodenkohlenstoffgehalt und Vegetationstyp abh��ngen. Basierend auf den daraus entwickelten statistischen Modellen betragen die globalen Emissionen aus Ackerb��den 3.3 Tg N/y f��r N2O, und 1.4 Tg N/y f��r NO. Solche statistischen Modelle sind n��tzlich, um Absch��tzungen und Unsicherheitsbereiche von N2O- und NO-Emissionen basierend auf einer Vielzahl von Messungen zu berechnen. Die Dynamik des Bodenstickstoffs, insbesondere beeinflusst durch Pflanzenwachstum, Klimawandel und Landnutzungs��nderung, kann allerdings nur durch die Anwendung von prozessorientierten Modellen ber��cksichtigt werden. Zur Modellierung von N2O-Emissionen mit dem Daycent-Modell wurde zun��chst dessen Spurengasmodul durch eine detailliertere Berechnung von Nitrifikation und Denitrifikation und die Ber��cksichtigung von Frost-Auftau-Emissionen weiterentwickelt. Diese ��berarbeitete Modellversion wurde dann an N2O-Emissionsmessungen unter verschiedenen Klimaten und Feldfr��chten getestet. Sowohl die Dynamik als auch die Gesamtsummen der N2O-Emissionen werden befriedigend abgebildet, wobei die Modelleffizienz f��r monatliche Mittelwerte zwischen 0.1 und 0.66 f��r die meisten Standorte liegt. Basierend auf der ��berarbeiteten Modellversion wurden die N2O-Emissionen f��r die zuvor parametrisierten Feldfr��chte berechnet. Emissionsraten und feldfruchtspezifische Unterschiede stimmen weitgehend mit Literaturangaben ��berein. D��ngemittelinduzierte Emissionen, die momentan vom IPCC mit 1.25 +/- 1% der eingesetzten D��ngemenge abgesch��tzt werden, reichen von 0.77% (Reis) bis 2.76% (Mais). Die Summe der berechneten Emissionen aus landwirtschaftlichen B��den betr��gt f��r die Mitte der 1990er Jahre 2.1 Tg N2O-N/y, was mit den Absch��tzungen aus anderen Studien ��bereinstimmt.

Efficient phosphorus application strategies for increased crop production in sub-Saharan West Africa

Comparable data are lacking from the range of environments found in sub-Saharan West Africa to draw more general conclusions about the relative merits of locally available rockphosphate (RockP) in alleviating phosphorus (P) constraints to crop growth. To fill this gap, a multi-factorial field experiment was conducted over 4 years at eight locations in Niger, Burkina Faso and Togo. These ranged in annual rainfall from 510 to 1300 mm. Crops grown were pearl millet (Pennisetum glaucum L.), sorghum (Sorghum bicolor (L.) Moench) and maize (Zea mays L.) either continuously or in rotation with cowpea (Vigna unguiculata Walp.) and groundnut (Arachis hypogaea L.). Crops were subjected to six P fertiliser treatments comprising RockP and soluble P at different rates and combined with 0 and 60 kg N ha^-1. For legumes, time trend analyses showed P-induced total dry matter (TDM) increases between 28 and 72% only with groundnut. Similarly, rotation-induced raises in cereal TDM compared to cereal monoculture were only observed with groundnut. For cereals, at the same rate of application, RockP was comparable to single superphosphate (SSP) only at two millet sites with topsoil pH-KCl <4.2 and annual average rainfall >600 mm. Across the eight sites NPK placement at 0.4 g P per hill raised average cereal yields between 26 and 220%. This was confirmed in 119 on-farm trials revealing P placement as a promising strategy to overcome P deficiency as the regionally most growth limiting nutrient constraint to cereals.

Phosphorus placement an acid arenosols of the West African Sahel

Phosphorus (P) deficiency is a major constraint to pearl millet (Pennisetum glaucum L.) growth on acid sandy soils of the West African Sahel. To develop cost-effective fertilization strategies for cash poor farmers, experiments with pearl millet were conducted in southwestern Niger. Treatments comprised single superphosphate hill-placed at rates of 1, 3, 5 or 7 kg P ha^���1 factorially combined with broadcast P at a rate of 13 kg ha^���1. Nitrogen was applied as calcium ammonium nitrate at rates of 30 and 45 kg ha^���1. At low soil moisture, placement of single superphosphate in immediate proximity to the seed reduced seedling emergence. Despite these negative effects on germination, P placement resulted in much faster growth of millet seedlings than did broadcast P. With P application, potassium nutrition of millet was improved and seedling nitrogen uptake increased two- to three-fold, indicating that nitrogen was not limiting early millet growth. Averaged over the 1995 and 1996 cropping seasons, placed applications of 3, 5 and 7 kg P ha^���1 led to 72%, 81% and 88% respectively, of the grain yield produced by broadcasting 13 kg P ha^���1. Nitrogen application did not show major effects on grain yield unless P requirements were met. A simple economic analysis revealed that the profitability of P application, defined as additional income per unit of fertilizer, was highest for P placement at 3 and 5 kg ha^���1.

Charakterisierung von M��hren und Weizen aus ��kologischem und konventionellem Anbau anhand ihrer Carotinoid- und Polyphenolkonzentration

Kurzfassung: Der Markt f��r ��kologische Lebensmittel w��chst stark. Verbraucher kaufen Produkte aus ��kologischem Landbau aus einer Vielzahl von Gr��nden. Ein Teil dieser Gr��nde l��sst sich nicht auf die Produktqualit��t zur��ckf��hren, sondern beruht auf der Annahme, dass sich der Produktionsprozess des ��kologischen Landbaus hinsichtlich der Schonung von Umweltressourcen, der Nachhaltigkeit der Produktion und sozialen Komponenten vom konventionellen Anbau unterscheidet. Daneben spielt der Wunsch nach einer gesunden Ern��hrung eine Rolle. ��kologische Lebensmittel k��nnen als Vertrauensg��ter verstanden werden. Lebensmittelskandale machten in den vergangenen Jahren auch vor ��kologischen Lebens��mitteln nicht Halt. Folgerichtig ersch��tterte dies das Vertrauen der Verbraucher in ��kologische Produkte. Mit steigender Produktion k��nnte die Gefahr, das weitere solche Ereignisse auftreten, steigen. Daher besteht Bedarf f��r Methoden, die die ��kologische Produktqualit��t im Sinne einer Authentizit��tspr��fung pr��fen. Eine solche Pr��fung k��nnte sich auf die Analyse sekund��rer Pflanzenstoffe st��tzen. Diese Gruppe von Pflanzeninhaltsstoffen spielt bei der Diskussion um die besondere Qualit��t ��kologischer Pflanzenprodukte eine gro��e Rolle. Postuliert wird, dass ��kologisch angebaute Pflanzen mangels mineralischer D��ngung und mangels Sch��dlingsbek��mpfung mit synthetischen Pestiziden einem erh��hten Stress ausgesetzt sind. Dies soll sich in einem h��heren Niveau der mit den Selbstverteidigungsmechanismen der Pflanze eng verbundenen sekund��ren Pflanzenstoffe ausdr��cken. Wichtige Untergruppen der sekund��ren Pflanzenstoffe sind Carotinoide und Polyphenole. An Weizen (Triticum aestivum L. und Triticum durum L.) und M��hre (Daucus carota L.) als f��r den ��kologischen Landbau wichtigen Produkten wurden Messungen der Carotinoid- und Polyphenolkonzentration mit dem Ziel durchgef��hrt, die potentielle Eignung dieser Pflanzenstoffe als Biomarker zur Authentizit��tspr��fung ��kologischer Produkte zu evaluieren. Dazu wurden Proben aus ��kologischem und konventionellem Anbau (Paarvergleich) untersucht. Diese stammten aus Langzeit-Feldversuchen (Weizen aus dem DOK- und dem MASCOT-Versuch), Feldversuchen und von Betriebspaaren untersucht. Ein generell h��heres Niveau sekund��rer Pflanzenstoffe in M��hren bzw. Weizen aus ��kologischem Anbau gegen��ber Proben aus konventionellem Anbau wurde nicht gefunden. Die Carotinoide waren weder bei der M��hre noch beim Weizen zur Authentizit��tspr��fung geeignet. Die Konzentration der Carotinoide wurde stark durch die nicht dem Anbau��verfahren zuzuordnenden Faktoren Klima, Sorte und Standort beeinflusst. Die Luteinkonzentration war das einzige durch das Anbauverfahren systematisch beeinflusste Carotenoid bei Weizen und M��hre. Die Unterschiede der Luteinkonzentration waren aber im Paarvergleich von Proben (��kologischer versus konventioneller Anbau) nicht durchg��ngig signifikant. Die Eignung von Polyphenolen als potentielles Authentizit��tskriterium wurde nur an M��hren gepr��ft. Im Paarvergleich unterschieden sich die Konzentrationen einzelner Polyphenole signifikant und konsistent ��ber Probenjahre und Standorte, nicht jedoch ��ber Sorten hinweg. Wie bei den Carotinoiden konnte auch hier ein starker Einfluss von Probenjahr, Standort und Sorte gezeigt werden. Trotz der Variation durch diese nicht dem Anbau zuzuordnenden Faktoren war eine korrekte Klassifizierung der Proben nach Anbauverfahren m��glich. Dies wurde mittels Diskriminanzanalyse getestet. Die Polyphenole sind daher potentiell als Authentizit��tskriterium geeignet.

Effects of fertilizer type and rate on partitioning of soil organic matter into pools of different stability

Type and rate of fertilizers influence the level of soil organic carbon (Corg) and total nitrogen (Nt) markedly, but the effect on C and N partitioning into different pools is open to question. The objectives of the present work were to: (i) quantify the impact of fertilizer type and rate on labile, intermediate and passive C and N pools by using a combination of biological, chemical and mathematical methods; (ii) explain previously reported differences in the soil organic matter (SOM) levels between soils receiving farmyard manure with or without biodynamic preparations by using Corg time series and information on SOM partitioning; and (iii) quantify the long-term and short-term dynamics of SOM in density fractions and microbial biomass as affected by fertilizer type and rate and determine the incorporation of crop residues into labile SOM fractions. Samples were taken from a sandy Cambisol from the long-term fertilization trial in Darmstadt, Germany, founded in 1980. The nine treatments (four field replicates) were: straw incorporation plus application of mineral fertilizer (MSI) and application of rotted farmyard manure with (DYN) or without (FYM) addition of biodynamic preparations, each at high (140 ��� 150 kg N ha-1 year-1; MSIH, DYNH, FYMH), medium (100 kg N ha-1 year-1; MSIM, DYNM, FYMM) and low (50 ��� 60 kg N ha-1 year-1; MSIL, DYNL, FYML) rates. The main findings were: (i) The stocks of Corg (t ha-1) were affected by fertilizer type and rate and increased in the order MSIL (23.6), MSIM (23.7), MSIH (24.2) < FYML (25.3) < FYMM (28.1), FYMH (28.1). Stocks of Nt were affected in the same way (C/N ratio: 11). Storage of C and N in the modelled labile pools (turnover times: 462 and 153 days for C and N, respectively) were not influenced by the type of fertilizer (FYM and MSI) but depended significantly (p ��� 0.05) on the application rate and ranged from 1.8 to 3.2 t C ha 1 (7 ��� 13% of Corg) and from 90 to 140 kg N ha-1 (4-5% of Nt). In the calculated intermediate pool (C/N ratio 7), stocks of C were markedly higher in FYM treatments (15-18 t ha-1) compared to MSI treatments (12-14 t ha-1). This showed that differences in SOM stocks in the sandy Cambisol induced by fertilizer rate may be short-lived in case of changing management, but differences induced by fertilizer type may persist for decades. (ii) Crop yields, estimated C inputs (1.5 t ha-1 year-1) with crop residue, microbial bio��mass C (Cmic, 118 ��� 150 mg kg-1), microbial biomass N (17 ��� 20 mg kg-1) and labile C and N pools did not differ significantly between FYM and DYN treatments. However, labile C increased linearly with application rate (R2 = 0.53) from 7 to 11% of Corg. This also applied for labile N (3.5 to 4.9% of Nt). The higher contents of Corg in DYN treatments existed since 1982, when the first sampling was conducted for all individual treatments. Contents of Corg between DYN and FYM treatments con-verged slightly since then. Furthermore, at least 30% of the difference in Corg was located in the passive pool where a treatment effect could be excluded. Therefore, the reported differences in Corg contents existed most likely since the beginning of the experiment and, as a single factor of biodynamic agriculture, application of bio-dynamic preparations had no effect on SOM stocks. (iii) Stocks of SOM, light fraction organic C (LFOC, �� ��� 2.0 g cm-3), light fraction organic N and Cmic decreased in the order FYMH > FYML > MSIH, MSIL for all sampling dates in 2008 (March, May, September, December). However, statistical significance of treatment effects differed between the dates, probably due to dif-ferences in the spatial variation throughout the year. The high proportion of LFOC on total Corg stocks (45 ��� 55%) highlighted the importance of selective preservation of OM as a stabilization mechanism in this sandy Cambisol. The apparent turnover time of LFOC was between 21 and 32 years, which agreed very well with studies with substantially longer vegetation change compared to our study. Overall, both approaches; (I) the combination of incubation, chemical fractionation and simple modelling and (II) the density fractionation; provided complementary information on the partitioning of SOM into pools of different stability. The density fractionation showed that differences in Corg stocks between FYM and MSI treatments were mainly located in the light fraction, i.e. induced by higher recalcitrance of the organic input in the FYM treatments. Moreover, the use of the combination of biological, chemical and mathematical methods indicated that effects of fertilizer rate on total Corg and Nt stocks may be short-lived, but that the effect of fertilizer type may persist for longer time spans in the sandy Cambisol.

Effects of Different Feeding Regimes on the Digestibility and Faecal Excretion of Nitrogen, Soluble Carbohydrates and Fibre Fractions in Water Buffaloes kept under Subtropical Conditions

In the course of the ���Livestock Revolution���, extension and intensification of, among others, ruminant livestock production systems are current phenomena, with all their positive and negative side effects. Manure, one of the inevitable secondary products of livestock rearing, is a valuable source of plant nutrients and its skillful recycling to the soil-plant interface is essential for soil fertility, nutrient - and especially phosphorus - uses efficiency and the preservation or re-establishment of environmentally sustainable farming systems, for which organic farming systems are exemplarily. Against this background, the PhD research project presented here, which was embedded in the DFG-funded Research Training Group 1397 ���Regulation of soil organic matter and nutrient turnover in organic agriculture ��� investigated possibilities to manipulate the diets of water buffalo (Bubalus bubalis L.) so as to produce manure of desired quality for organic vegetable production, without affecting the productivity of the animals used. Consisting of two major parts, the first study (chapter 2) tested the effects of diets differing in their ratios of carbon (C) to nitrogen (N) and of structural to non-structural carbohydrates on the quality of buffalo manure under subtropical conditions in Sohar, Sultanate of Oman. To this end, two trials were conducted with twelve water buffalo heifers each, using a full Latin Square design. One control and four tests diets were examined during three subsequent 7 day experimental periods preceded each by 21 days adaptation. Diets consisted of varying proportions of Rhodes grass hay, soybean meal, wheat bran, maize, dates, and a commercial concentrate to achieve a (1) high C/N and high NDF (neutral detergent fibre)/SC (soluble carbohydrate) ratio (HH), (2) low C/N and low NDF/SC ratio (LL); (3) high C/N and low NDF/SC ratio (HL) and (4) low C/N and high NDF/SC (LH) ratio. Effects of these diets, which were offered at 1.45 times maintenance requirements of metabolizable energy, and of individual diet characteristics, respectively, on the amount and quality of faeces excreted were determined and statistically analysed. The faeces produced from diets HH and LL were further tested in a companion PhD study (Mr. K. Siegfried) concerning their nutrient release in field experiments with radish and cabbage. The second study (chapter 3) focused on the effects of the above-described experimental diets on the rate of passage of feed particles through the gastrointestinal tract of four randomly chosen animals per treatment. To this end, an oral pulse dose of 683 mg fibre particles per kg live weight marked with Ytterbium (Yb; 14.5 mg Yb g-1 organic matter) was dosed at the start of the 7 day experimental period which followed 21 days of adaptation. During the first two days a sample for Yb determination was kept from each faecal excretion, during days 3 ��� 7 faecal samples were kept from the first morning and the first evening defecation only. Particle passage was modelled using a one-compartment age-dependent Gamma-2 model. In both studies individual feed intake and faecal excretion were quantified throughout the experimental periods and representative samples of feeds and faeces were subjected to proximate analysis following standard protocols. In the first study the organic matter (OM) intake and excretion of LL and LH buffaloes were significantly lower than of HH and HL animals, respectively. Digestibility of N was highest in LH (88%) and lowest in HH (74%). While NDF digestibility was also highest in LH (85%) it was lowest in LL (78%). Faecal N concentration was positively correlated (P���0.001) with N intake, and was significantly higher in faeces excreted by LL than by HH animals. Concentrations of fibre and starch in faecal OM were positively affected by the respective dietary concentrations, with NDF being highest in HH (77%) and lowest in LL (63%). The faecal C/N ratio was positively related (P���0.001) to NDF intake; C/N ratios were 12 and 7 for HH and LL (P���0.001), while values for HL and LH were 11.5 and 10.6 (P>0.05). The results from the second study showed that dietary N concentration was positively affecting faecal N concentration (P���0.001), while there was a negative correlation with the faecal concentration of NDF (P���0.05) and the faecal ratios of NDF/N and C/N (P���0.001). Particle passage through the mixing compartment was lower (P���0.05) for HL (0.033 h-1) than for LL (0.043 h-1) animals, while values of 0.034 h-1 and 0.038 h-1 were obtained for groups LH and HH. At 55.4 h, total tract mean retention time was significantly (P���0.05) lower in group LL that in all other groups where these values varied between 71 h (HH) and 79 h (HL); this was probably due to the high dietary N concentration of diet LL which was negatively correlated with time of first marker appearance in faeces (r= 0.84, P���0.001), while the dietary C concentration was negatively correlated with particle passage through the mixing compartment (r= 0.57, P���0.05). The results suggest that manure quality of river buffalo heifers can be considerably influenced by diet composition. Despite the reportedly high fibre digestion capacity of buffalo, digestive processes did not suppress the expression of diet characteristics in the faeces. This is important when aiming at producing a specific manure quality for fertilization purposes in (organic) crop cultivation. Although there was a strong correlation between the ingestion and the faecal excretion of nitrogen, the correlation between diet and faecal C/N ratio was weak. To impact on manure mineralization, the dietary NDF and N concentrations seem to be the key control points, but modulating effects are achieved by the inclusion of starch into the diet. Within the boundaries defined by the animals��� metabolic and (re)productive requirements for energy and nutrients, diet formulation may thus take into account the abiotically and biotically determined manure turnover processes in the soil and the nutrient requirements of the crops to which the manure is applied, so as to increase nutrient use efficiency along the continuum of the feed, the animal, the soil and the crop in (organic) farming systems.

Clay pot irrigation for tomato (Lycopersicon esculentum Mill) production in the north east semiarid region of Ethiopia

Water shortage is one of the major constraints for production of horticultural crops in arid and semiarid regions. A field experiment was conducted to determine irrigation water and fertilizer use efficiency, growth and yield of tomato under clay pot irrigation at the experimental site of Sekota Dryland Agricultural Research Center, Lalibela, Ethiopia in 2009/10. The experiment comprised of five treatments including furrow irrigated control and clay pot irrigation with different plant population and fertilization methods, which were arranged in Randomized Complete Block Design with three replications. The highest total and marketable fruit yields were obtained from clay pot irrigation combined with application of nitrogen fertilizer with irrigation water irrespective of difference in plant population. The clay pot irrigation had seasonal water use of up to 143.71 mm, which resulted in significantly higher water use efficiency (33.62 kg m^-3) as compared to the furrow irrigation, which had a seasonal water use of 485.50 mm, and a water use efficiency of 6.67 kg m^-3. Application of nitrogen fertilizer with irrigation water in clay pots improved fertilizer use efficiency of tomato by up to 52% than band application with furrow or clay pot irrigation. Thus, clay pot irrigation with 33,333 plants ha^-1 and nitrogen fertilizer application with irrigation water in clay pots was the best method for increasing the yield of tomato while economizing the use of water and nitrogen fertilizer in a semiarid environment.

Nitrogen in combination with Desmodium intortum effectively suppress Striga asiatica in a sorghum���Desmodium intercropping system

It is well known that the parasitic weed Striga asiatica (L.) Kuntze can be suppressed by Striga-tolerant sorghum (Sorghum bicolor L. Moench) cultivars, Desmodium intortum (Mill.) Urb. (greanleaf desmodium), and by fertilization with nitrogen. The study objective was the assessment of Striga control provided by integration of Desmodium density, timing of sorghum-Desmodium intercrop establishment, and nitrogen fertilization. Growth responses and yield of three sorghum cultivars were measured in three pot experiments. A soil naturally infested with Striga was used, and that part of the soil which served as uninfested control was chemically sterilised. Striga numbers and growth were affected significantly by sorghum cultivars, sorghum-Desmodium intercrop ratios, timing of the sorghum-Desmodium association, as well as by their interactions. Desmodium caused 100% suppression of Striga emergence when Desmodium was established in the 1:3 sorghum-Desmodium ratio at seeding of sorghum. Total control of Striga was also achieved with the 1:1 sorghum-Desmodium ratio when Desmodium was transplanted 30 days before sorghum seeding. However, these two treatments also caused significant reductions in sorghum yield. In contrast, 100% Striga control and a dramatic increase in sorghum yield were achieved with 100 kg N ha^{-1} in the 1:1 sorghum-Desmodium intercrop. Compatibility of sorghum and Desmodium was evident at the 1:1 sorghum-Desmodium intercrop established at sorghum seeding. Overall, the Ethiopian cultivars Meko and Abshir showed better agronomic performance and higher tolerance to Striga than the South African cultivar PAN 8564. It is recommended that the N �� Desmodium �� sorghum interaction be investigated under field conditions.

Matter flows and balances in urban vegetable gardens of Bobo Dioulasso, Burkina Faso (West Africa)

Many efforts are undertaken for sustaining urban agriculture in African cities. This study therefore investigated nutrient management practices in urban vegetable gardens of Bobo Dioulasso, Burkina Faso (West Africa). Nitrogen (N), phosphorus (P), potassium (K), and carbon (C) fluxes were quantified and nutrient balances calculated for three gardens representing the typical commercial gardening + field crops and livestock system (cGCL) and three gardens representing the commercial gardening + semi-commercial field crop system (cGscC). Nutrient and C balances were similarly positive in both production systems reaching annual averages of 688 kg N ha -1, 251 kg P ha-1 yr-1, 189 kg K ha-1, and 31 t C ha-1. Inputs in all gardens exceeded the amounts recommended by the extension service. Gaseous emissions of N and C represented important pathways of N and C losses. The highest emission rates occurred during the hottest periods of the day and the peaks were observed after fertilizer applications. Management recommendations should be geared towards increasing nutrient use efficiencies by better tailoring nutrient availability to crop demand and adjusted fertilization techniques to mitigate N losses.

Application of biogas slurries from energy crops to arable soils and their impact on carbon and nitrogen dynamics

The use of renewable primary products as co-substrate or single substrate for biogas production has increased consistently over the last few years. Maize silage is the preferential energy crop used for fermentation due to its high methane (CH4) yield per hectare. Equally, the by-product, namely biogas slurry (BS), is used with increasing frequency as organic fertilizer to return nutrients to the soil and to maintain or increase the organic matter stocks and soil fertility. Studies concerning the application of energy crop-derived BS on the carbon (C) and nitrogen (N) mineralization dynamics are scarce. Thus, this thesis focused on the following objectives: I) The determination of the effects caused by rainfall patterns on the C and N dynamics from two contrasting organic fertilizers, namely BS from maize silage and composted cattle manure (CM), by monitoring emissions of nitrous oxide (N2O), carbon dioxide (CO2) and CH4 as well as leaching losses of C and N. II) The investigation of the impact of differences in soil moisture content after the application of BS and temperature on gaseous emissions (CO2, N2O and CH4) and leaching of C and N compounds. III) A comparison of BS properties obtained from biogas plants with different substrate inputs and operating parameters and their effect on C and N dynamics after application to differently textured soils with varying application rates and water contents. For the objectives I) and II) two experiments (experiment I and II) using undisturbed soil cores of a Haplic Luvisol were carried out. Objective III) was studied on a third experiment (experiment III) with disturbed soil samples. During experiment I three rainfall patterns were implemented including constant irrigation, continuous irrigation with periodic heavy rainfall events, and partial drying with rewetting periods. Biogas slurry and CM were applied at a rate of 100 kg N ha-1. During experiment II constant irrigation and an irrigation pattern with partial drying with rewetting periods were carried out at 13.5��C and 23.5��C. The application of BS took place either directly before a rewetting period or one week after the rewetting period stopped. Experiment III included two soils of different texture which were mixed with ten BS���s originating from ten different biogas plants. Treatments included low, medium and high BS-N application rates and water contents ranging from 50% to 100% of water holding capacity (WHC). Experiment I and II showed that after the application of BS cumulative N2O emissions were 4 times (162 mg N2O-N m-2) higher compared to the application of CM caused by a higher content of mineral N (Nmin) in the form of ammonium (NH4+) in the BS. The cumulative emissions of CO2, however, were on the same level for both fertilizers indicating similar amounts of readily available C after composting and fermentation of organic material. Leaching losses occurred predominantly in the mineral form of nitrate (NO3-) and were higher in BS amended soils (9 mg NO3--N m-2) compared to CM amended soils (5 mg NO3--N m-2). The rainfall pattern in experiment I and II merely affected the temporal production of C and N emissions resulting in reduced CO2 and enhanced N2O emissions during stronger irrigation events, but showed no effect on the cumulative emissions. Overall, a significant increase of CH4 consumption under inconstant irrigation was found. The time of fertilization had no effect on the overall C and N dynamics. Increasing temperature from 13.5��C to 23.5��C enhanced the CO2 and N2O emissions by a factor of 1.7 and 3.7, respectively. Due to the increased microbial activity with increasing temperature soil respiration was enhanced. This led to decreasing oxygen (O2) contents which in turn promoted denitrification in soil due to the extension of anaerobic microsites. Leaching losses of NO3- were also significantly affected by increasing temperature whereas the consumption of CH4 was not affected. The third experiment showed that the input materials of biogas plants affected the properties of the resulting BS. In particular the contents of DM and NH4+ were determined by the amount of added plant biomass and excrement-based biomass, respectively. Correlations between BS properties and CO2 or N2O emissions were not detected. Solely the ammonia (NH3) emissions showed a positive correlation with NH4+ content in BS as well as a negative correlation with the total C (Ct) content. The BS-N application rates affected the relative CO2 emissions (% of C supplied with BS) when applied to silty soil as well as the relative N2O emissions (% of N supplied with BS) when applied to sandy soil. The impacts on the C and N dynamics induced by BS application were exceeded by the differences induced by soil texture. Presumably, due to the higher clay content in silty soils, organic matter was stabilized by organo-mineral interactions and NH4+ was adsorbed at the cation exchange sites. Different water contents induced highest CO2 emissions and therefore optimal conditions for microbial activity at 75% of WHC in both soils. Cumulative nitrification was also highest at 75% and 50% of WHC whereas the relative N2O emissions increased with water content and showed higher N2O losses in sandy soils. In summary it can be stated that the findings of the present thesis confirmed the high fertilizer value of BS���s, caused by high concentrations of NH4+ and labile organic compounds such as readily available carbon. These attributes of BS���s are to a great extent independent of the input materials of biogas plants. However, considerably gaseous and leaching losses of N may occur especially at high moisture contents. The emissions of N2O after field application corresponded with those of animal slurries.

Effects of Organic and Inorganic Fertilizers on Growth and Yield of Banana (Musa AAA cv. Malindi) in Oman

The Sultanate of Oman is located on the south-eastern coast of the Arabian Peninsula, which lies on the south-western tip of the Asian continent. The strategic geographical locations of the Sultanate with its many maritime ports distributed on the Indian Ocean have historically made it one of the Arabian Peninsula leaders in the international maritime trade sector. Intensive trading relationships over long time periods have contributed to the high plant diversity seen in Oman where agricultural production depends entirely on irrigation from groundwater sources. As a consequence of the expansion of the irrigated area, groundwater depletion has increased, leading to the intrusion of seawater into freshwater aquifers. This phenomenon has caused water and soil salinity problems in large parts of the Al-Batinah governorate of Oman and threatens cultivated crops, including banana (Musa spp.). According to the Ministry of Agriculture and Fisheries, the majority of South Al-Batinah farms are affected by salinity (ECe > 4 dS m-1). As no alternative farmland is available, the reclamation of salt-affected soils using simple cultural practices is of paramount importance, but in Oman little scientific research has been conducted to develop such methods of reclamation. This doctoral study was initiated to help filling this research gap, particularly for bananas. A literature review of the banana cultivation history revealed that the banana germplasm on the Arabian Peninsula is probably introduced from Indonesia and India via maritime routes across the Indian Ocean and the Red Sea. In a second part of this dissertation, two experiments are described. A laboratory trial conducted at the University of Kassel, in Witzenhausen, Germany from June to July 2010. This incubation experiment was done to explore how C and N mineralization of composted dairy manure and date palm straw differed in alkaline non-saline and saline soils. Each soil was amended with four organic fertilizers: 1) composted dairy manure, 2) manure + 10% date palm straw, 3) manure + 30% date palm straw or 4) date palm straw alone, in addition to un-amended soils as control. The results showed that the saline soil had a lower soil organic C content and microbial biomass C than the non-saline soil. This led to lower mineralization rates of manure and date palm straw in the saline soil. In the non-saline soil, the application of manure and straw resulted in significant increases of CO2 emissions, equivalent to 2.5 and 30% of the added C, respectively. In the non-amended control treatment of the saline soil, the sum of CO2-C reached only 55% of the soil organic C in comparison with the non-saline soil. In which 66% of the added manure and 75% of the added straw were emitted, assuming that no interactions occurred between soil organic C, manure C and straw C during microbial decomposition. The application of straw always led to a net N immobilization compared to the control. Salinity had no specific effect on N mineralization as indicated by the CO2-C to Nmin ratio of soil organic matter and manure. However, N immobilization was markedly stronger in the saline soil. Date palm straw strongly promoted saprotrophic fungi in contrast to manure and the combined application of manure and date palm straw had synergistic positive effects on soil microorganisms. In the last week of incubation, net-N mineralization was observed in nearly all treatments. The strongest increase in microbial biomass C was observed in the manure + straw treatment. In both soils, manure had no effect on the fungi-specific membrane component ergosterol. In contrast, the application of straw resulted in strong increases of the ergosterol content. A field experiment was conducted on two adjacent fields at the Agricultural Research Station, Rumais (23��41���15��� N, 57��59���1��� E) in the South of Al-Batinah Plain in Oman from October 2007 to July 2009. In this experiment, the effects of 24 soil and fertilizer treatments on the growth and productivity of Musa AAA cv. 'Malindi' were evaluated. The treatments consisted of two soil types (saline and amended non-saline), two fertilizer application methods (mixed and ring applied), six fertilizer amendments (1: fresh dairy manure, 2: composted dairy manure, 3: composted dairy manure and 10% date palm straw, 4: composted dairy manure and 30% date palm straw, 5: only NPK, and 6: NPK and micronutrients). Sandy loam soil was imported from another part of Oman to amended the soil in the planting holes and create non-saline conditions in the root-zone. The results indicate that replacing the saline soil in the root zone by non-saline soil improved plant growth and yield more than fertilizer amendments or application methods. Particularly those plants on amended soil where NPK was applied using the ring method and which received micronutrients grew significantly faster to harvest (339 days), had a higher average bunch weight (9.5 kg/bunch) and were consequently more productive (10.6 tonnes/hectare/cycle) compared to the other treatments.

Sensorische Erfassung von Gr��nlandbiomassen als Grundlage f��r ein teilfl��chenspezifisches Management im ��kologischen Landbau

Vor dem Hintergund der Integration des wissensbasierten Managementsystems Precision Farming in den ��kologischen Landbau wurde die Umsetzung bestehender sowie neu zu entwickelnder Strategien evaluiert und diskutiert. Mit Blick auf eine im Precision Farming ma��gebende kosteneffiziente Ertragserfassung der im ��kologischen Landbau fl��chenrelevanten Leguminosen-Grasgemenge wurden in zwei weiteren Beitr��gen die Sch��tzg��ten von Ultraschall- und Spektralsensorik in singul��rer und kombinierter Anwendung analysiert. Das Ziel des Precision Farming, ein angepasstes Management bezogen auf die fl��cheninterne Variabilit��t der Standorte umzusetzen, und damit einer Reduzierung von Betriebsmitteln, Energie, Arbeit und Umwelteffekten bei gleichzeitiger Effektivit��tssteigerung und einer ��konomischen Optimierung zu erreichen, deckt sich mit wesentlichen Bestrebungen im ��kogischen Landbau. Es sind vorrangig Ma��nahmen zur Erfassung der Variabilit��t von Standortfaktoren wie Gel��nderelief, Bodenbeprobung und scheinbare elektrische Leitf��higkeit sowie der Ertragserfassung ��ber M��hdrescher, die direkt im ��kologischen Landbau Anwendung finden k��nnen. Dagegen sind dynamisch angepasste Applikationen zur D��ngung, im Pflanzenschutz und zur Beseitigung von Unkr��utern aufgrund komplexer Interaktionen und eines eher passiven Charakters dieser Ma��nahmen im ��kologischen Landbau nur bei Ver��nderung der Applikationsmodelle und unter Einbindung weiterer dynamischer Daten umsetzbar. Beispiele hief��r sind einzubeziehende Mineralisierungsprozesse im Boden und organischem D��nger bei der D��ngemengenberechnung, schwer ortsspezifisch zuzuordnende pr��ventive Ma��namen im Pflanzenschutz sowie Einfl��sse auf bodenmikrobiologische Prozesse bei Hack- oder Striegelg��ngen. Die indirekten Regulationsmechanismen des ��kologischen Landbaus begrenzen daher die bisher eher auf eine direkte Wirkung ausgelegten dynamisch angepassten Applikationen des konventionellen Precision Farming. Erg��nzend sind innovative neue Strategien denkbar, von denen die qualit��tsbezogene Ernte, der Einsatz hochsensibler Sensoren zur Fr��herkennung von Pflanzenkrankheiten oder die gezielte teilfl��chen- und naturschutzorientierte Bewirtschaftung exemplarisch in der Arbeit vorgestellt werden. F��r die h��ufig gro��e Fl��chenanteile umfassenden Leguminosen-Grasgemenge wurden f��r eine kosteng��nstige und flexibel einsetzbare Ertragserfassung die Ultraschalldistanzmessung zur Charakterisierung der Bestandesh��he sowie verschiedene spektrale Vegetationsindices als Sch��tzindikatoren analysiert. Die Vegetationsindices wurden aus hyperspektralen Daten nach publizierten Gleichungen errechnet sowie als ���Normalized Difference Spectral Index��� (NDSI) stufenweise aus allen m��glichen Wellenl��ngenkombinationen ermittelt. Die Analyse erfolgte f��r Ultraschall und Vegetationsindices in alleiniger und in kombinierter Anwendung, um m��gliche kompensatorische Effekte zu nutzen. In alleiniger Anwendung erreichte die Ultraschallbestandesh��he durchweg bessere Sch��tzg��ten, als alle einzelnen Vegetationsindices. Bei den letztgenannten erreichten insbesondere auf Wasserabsorptionsbanden basierende Vegetationsindices eine h��here Sch��tzgenauigkeit als traditionelle Rot/Infrarot-Indices. Die Kombination beider Sensorda-ten lie�� eine weitere Steigerung der Sch��tzg��te erkennen, insbesondere bei bestandesspezifischer Kalibration. Hierbei kompensieren die Vegetationsindices Fehlsch��tzungen der H��henmessung bei diskontinuierlichen Bestandesdichten��nderungen entlang des H��hengradienten, wie sie beim ��hrenschieben oder durch einzelne hochwachsende Arten verursacht werden. Die Kombination der Ultraschallbestandesh��he mit Vegetationsindices weist das Potential zur Entwicklung kosteng��nstiger Ertragssensoren f��r Leguminosen-Grasgemenge auf. Weitere Untersuchungen mit hyperspektralen Vegetationsindices anderer Berechnungstrukturen sowie die Einbindung von mehr als zwei Wellenl��ngen sind hinsichtlich der Entwicklung h��herer Sch��tzg��ten notwendig. Ebenso gilt es, Kalibrierungen und Validationen der Sensorkombination im artenreichen Grasland durchzuf��hren. Die Ertragserfassung in den Leguminosen-Grasgemengen stellt einen wichtigen Beitrag zur Erstellung einer Ertragshistorie in den vielf��ltigen Fruchtfolgen des ��kologischen Landbaus dar und erm��glicht eine verbesserte Einsch��tzung von Produktionspotenzialen und Defizitarealen f��r ein standortangepasstes Management.

Nitrogen requirements of cassava in selected soils of Thailand

Cassava (Manihot esculenta) is one of the most important export crops in Thailand, yet the nitrogen requirement is unknown and not considered by growers and producers. Cassava requirements for N were determined in field experiments during a period of four years and four sites on the Satuk (Suk), Don Chedi (Dc), Pak Chong (Pc),and Ban Beung (BBg) soil series in Lopburi, Supanburi, Nakhon Ratchasima, and Chonburi sites, respectively. The fertilizer treatment structure comprised 0, 62.5, 125, 187.5, 250 and 312.5 kg N ha^(-1) as urea. At each site cassava was harvested at nine months and yield parameters and the minimum datasets were taken. The fertilizer rate which resulted in maximum yield ranged from 187.5 kg N ha^(-1) in Supanburi and Chonburi (fresh weight yield of 47,500 and 30,000 kg ha^(-1) respectively) to 250 kg N ha^(-1) in Lopburi and Nakhon Ratchasima (fresh weight yield of 64,100 and 46,700 kg ha^(-1) respectively). Yield appeared to decrease at the higher, 312 kg ha^(-1), at Supanburi and Lopburi, and 250 kg ha^(-1) (Chonburi) fertilizer N rates. Net revenue was 70.4 and 72.9 % higher than where no N was appliedLopburi and Nakhon Ratchasima sites. Net revenue at the Supanburi and Chonburi sites were 53.8 and 211.0 % higher than that where no N was applied. This study suggests that at all sites improved cassava production and net revenue could be obtained with the judicious application of higher quantities of N. The results provide needed guidance to nitrogen fertilization of the important industrial crop cassava in Thailand.