Fertilizer 15N balance in a coffee cropping system: a case study in Brazil

Knowledge about the fate of fertilizer nitrogen in agricultural systems is essential for the improvement of management practices in order to maximize nitrogen (N) recovery by the crop and reduce N losses from the system to a minimum. This study involves fertilizer management practices using the 15N isotope label applied in a single rate to determine the fertilizer-N balance in a particular soil-coffee-atmosphere system and to deepen the understanding of N plant dynamics. Five replicates consisting of plots of about 120 plants each were randomly defined within a 0.2 ha coffee plantation planted in 2001, in Piracicaba, SP, Brazil. Nine plants of each plot were separated in sub-plots for the 15N balance studies and treated with N rates of 280 and 350 kg ha-1 during 2003/2004 and 2004/2005, respectively, both of them as ammonium sulfate enriched to a 15N abundance of 2.072 atom %. Plant shoots were considered as separate parts: the orthotropic central branch, productive branches, leaves of productive branches, vegetative branches, leaves of vegetative branches and fruit. Litter, consisting of dead leaves accumulated below the plant canopy, was measured by the difference between leaves at harvest and at the beginning of the following flowering. Roots and soil were sampled down to a depth of 1.0 at intervals of 0.2 m. Samples from the isotopic sub-plots were used to evaluate total N and 15N, and plants outside sub-plots were used to evaluate dry matter. Volatilization losses of NH3 were estimated using special collectors. Leaching of fertilizer-N was estimated from deep drainage water fluxes and 15N concentrations of the soil solution at 1 m soil depth. At the end of the 2-year evaluation, the recovery of 15N applied as ammonium sulfate was 19.1 % in aerial plant parts, 9.4 % in the roots, 23.8 % in the litter, 26.3 % in the fruit and 12.6 % remaining in the 0_1.0 m soil profile. Annual leaching and volatilization losses were very small (2.0 % and 0.9 %, respectively). After two years, only 6.2 % N were missing in the balance (100 %) which can be attributed to other non-estimated compartments and experimental errors. Results show that an enrichment of only 2 % atom 15N allows the study of the partition of fertilizer-N in a perennial crop such as coffee during a period of two years.

Utilization of Boron (10B) derived from fertilizer by sugar cane

The response to B in agricultural systems of sugar cane is still an unexplored issue; B application has however recently been widely publicized and used with a certain degree of frequency. The use of 10B-labeled fertilizers may further contribute to clarify this practice. With the objective of evaluating sugar cane use of B (10B) derived from fertilizer (boric acid), an experiment was conducted under field conditions in the 2005/2006 growing season. The experiment consisted of the installation of microplots (2 x 1.5 m) where 4 kg ha-1 B (boric acid with 85.95 % in 10B atoms) dissolved in water was applied 90 days after planting (May 2005). The solution was applied to the soil on both sides of the plant row at a distance of 20 cm. After harvest (June 2006) the B content and 10B abundance in % atoms in all parts of the sugar cane plants (stalks, dry leaves, tips and roots) were determined. Results showed that the total B accumulated was 471 g ha-1 in the entire plant (35 % in the stalks, 22 % in the dry leaves, 9 % in the tips and 34 % in the roots). The sugar cane plants used on average 14 % of the total accumulated B in the above-ground part (44 g ha-1) and 11 % in the roots (19 g ha-1), totaling 13 % in the entire plant (63 g ha-1). The recovery of 10B-fertilizer by sugar cane plants was low, around 2 % of the total applied amount.

Spatial variability of physical attributes of an alfisol under different hillslope curvatures

The influence of relief forms has been studied by several authors and explains the variability in the soil attributes of a landscape. Soil physical attributes depend on relief forms, and their assessment is important in mechanized agricultural systems, such as of sugarcane. This study aimed to characterize the spatial variability in the physical soil attributes and their relationship to the hillslope curvatures in an Alfisol developed from sandstone and growing sugarcane. Grids of 100 x 100 m were delimited in a convex and a concave area. The grids had a regular spacing of 10 x 10 m, and the crossing points of this spacing determined a total of 121 georeferenced sampling points. Samples were collected to determine the physical attributes related to soil aggregates, porosity, bulk density, resistance to penetration and moisture within the 0-0.2 and 0.2-0.4 m depth. Statistical analyses, geostatistics and Student's t-tests were performed with the means of the areas. All attributes, except aggregates > 2 mm in the 0-0.2 m depth and macroporosity at both depths, showed significant differences between the hillslope curvatures. The convex area showed the highest values of the mean weighted diameter, mean geometric diameter, aggregates > 2 mm, 1-2 mm aggregates, total porosity and moisture and lower values of bulk density and resistance to penetration in both depth compared to the concave area. The number of soil attributes with greater spatial variability was higher in the concave area.

Nitrogen washing from C3 and C4 cover grasses residues by rain

Crop species with the C4 photosynthetic pathway are more efficient in assimilating N than C3 plants, which results in different N amounts prone to be washed from its straw by rain water. Such differences may affect N recycling in agricultural systems where these species are grown as cover crops. In this experiment, phytomass production and N leaching from the straw of grasses with different photosynthetic pathways were studied in response to N application. Pearl millet (Pennisetum glaucum) and congo grass (Brachiaria ruziziensis) with the C4 photosynthetic pathway, and black oat (Avena Strigosa) and triticale (X Triticosecale), with the C3 photosynthetic pathway, were grown for 47 days. After determining dry matter yields and N and C contents, a 30 mm rainfall was simulated over 8 t ha-1 of dry matter of each plant residue and the leached amounts of ammonium and nitrate were determined. C4 grasses responded to higher fertilizer rates, whereas N contents in plant tissue were lower. The amount of N leached from C4 grass residues was lower, probably because the C/N ratio is higher and N is more tightly bound to organic compounds. When planning a crop rotation system it is important to take into account the difference in N release of different plant residues which may affect N nutrition of the subsequent crop.

New methods to quantify NH3 volatilization from fertilized surface soil with urea

Gaseous N losses from soil are considerable, resulting mostly from ammonia volatilization linked to agricultural activities such as pasture fertilization. The use of simple and accessible measurement methods of such losses is fundamental in the evaluation of the N cycle in agricultural systems. The purpose of this study was to evaluate quantification methods of NH3 volatilization from fertilized surface soil with urea, with minimal influence on the volatilization processes. The greenhouse experiment was arranged in a completely randomized design with 13 treatments and five replications, with the following treatments: (1) Polyurethane foam (density 20 kg m-3) with phosphoric acid solution absorber (foam absorber), installed 1, 5, 10 and 20 cm above the soil surface; (2) Paper filter with sulfuric acid solution absorber (paper absorber, 1, 5, 10 and 20 cm above the soil surface); (3) Sulfuric acid solution absorber (1, 5 and 10 cm above the soil surface); (4) Semi-open static collector; (5) 15N balance (control). The foam absorber placed 1 cm above the soil surface estimated the real daily rate of loss and accumulated loss of NH3N and proved efficient in capturing NH3 volatized from urea-treated soil. The estimates based on acid absorbers 1, 5 and 10 cm above the soil surface and paper absorbers 1 and 5 cm above the soil surface were only realistic for accumulated N-NH3 losses. Foam absorbers can be indicated to quantify accumulated and daily rates of NH3 volatilization losses similarly to an open static chamber, making calibration equations or correction factors unnecessary.

Incubation methods for assessing mineralizable nitrogen in soils under sugarcane

Considering nitrogen mineralization (N) of soil organic matter is a key aspect for the efficient management of N fertilizers in agricultural systems. Long-term aerobic incubation is the standard technique for calibrating the chemical extraction methods used to estimate the potentially mineralizable N in soil. However, the technique is laborious, expensive and time-consuming. In this context, the aims of this study were to determine the amount of soil mineralizable N in the 0-60 cm layer and to evaluate the use of short-term anaerobic incubation instead of long-term aerobic incubation for the estimation of net N mineralization rates in soils under sugarcane. Five soils from areas without previous N fertilization were used in the layers 0-20, 20-40 and 40-60 cm. Soil samples were aerobically incubated at 35 ºC for 32 weeks or anaerobically incubated (waterlogged) at 40 ºC for seven days to determine the net soil N mineralization. The sand, silt and clay contents were highly correlated with the indexes used for predicting mineralizable N. The 0-40 cm layer was the best sampling depth for the estimation of soil mineralizable N, while in the 40-60 cm layer net N mineralization was low in both incubation procedures. Anaerobic incubation provided reliable estimates of mineralizable N in the soil that correlated well with the indexes obtained using aerobic incubation. The inclusion of the pre-existing NH4+-N content improved the reliability of the estimate of mineralizable N obtained using anaerobic incubation.

Physical quality of an Oxisol under an integrated crop-livestock-forest system in the Brazilian Cerrado

Soil physical quality is an important factor for the sustainability of agricultural systems. Thus, the aim of this study was to evaluate soil physical properties and soil organic carbon in a Typic Acrudox under an integrated crop-livestock-forest system. The experiment was carried out in Mato Grosso do Sul, Brazil. Treatments consisted of seven systems: integrated crop-livestock-forest, with 357 trees ha-1 and pasture height of 30 cm (CLF357-30); integrated crop-livestock-forest with 357 trees ha-1 and pasture height of 45 cm (CLF357-45); integrated crop-livestock-forest with 227 trees ha-1 and pasture height of 30 cm (CLF227-30); integrated crop-livestock-forest with 227 trees ha-1 and pasture height of 45 cm (CLF227-45); integrated crop-livestock with pasture height of 30 cm (CL30); integrated crop-livestock with pasture height of 45 cm (CL45) and native vegetation (NV). Soil properties were evaluated for the depths of 0-10 and 10-20 cm. All grazing treatments increased bulk density (r b) and penetration resistance (PR), and decreased total porosity (¦t) and macroporosity (¦ma), compared to NV. The values of r b (1.18-1.47 Mg m-3), ¦ma (0.14-0.17 m³ m-3) and PR (0.62-0.81 MPa) at the 0-10 cm depth were not restrictive to plant growth. The change in land use from NV to CL or CLF decreased soil organic carbon (SOC) and the soil organic carbon pool (SOCpool). All grazing treatments had a similar SOCpool at the 0-10 cm depth and were lower than that for NV (17.58 Mg ha-1).

NITROGEN LOSS BY EROSION FROM MECHANICALLY TILLED AND UNTILLED SOIL UNDER SUCCESSIVE SIMULATED RAINFALLS

The description of the fate of fertilizer-derived nitrogen (N) in agricultural systems is an essential tool to enhance management practices that maximize nutrient use by crops and minimize losses. Soil erosion causes loss of nutrients such as N, causing negative effects on surface and ground water quality, aside from losses in agricultural productivity by soil depletion. Studies correlating the percentage of fertilizer-derived N (FDN) with soil erosion rates and the factors involved in this process are scarce. The losses of soil and fertilizer-derived N by water erosion in soil under conventional tillage and no tillage under different rainfall intensities were quantified, identifying the intervening factors that increase loss. The experiment was carried out on plots (3.5 × 11 m) with two treatments and three replications, under simulated rainfall. The treatments consisted of soil with and soil without tillage. Three successive rainfalls were applied in intervals of 24 h, at intensities of 30 mm/h, 30 mm/h and 70 mm/h. The applied N fertilizer was isotopically labeled (15N) and incorporated into the soil in a line perpendicular to the plot length. Tillage absence resulted in higher soil losses and higher total nitrogen losses (TN) by erosion induced by the rainfalls. The FDN losses followed another pattern, since FDN contributions were highest from tilled plots, even when soil and TN losses were lowest, i.e., the smaller the amount of eroded sediment, the greater the percentage of FDN associated with these. Rain intensity did not affect the FDN loss, and losses were greatest after less intense rainfalls in both treatments.

Sugarcane crop efficiency in two growing seasons in São Paulo State, Brazil

A conceptual framework for crop production efficiency was derived using thermodynamic efficiency concept, in order to generate a tool for performance evaluation of agricultural systems and to quantify the interference of determining factors on this performance. In Thermodynamics, efficiency is the ratio between the output and input of energy. To establish this relationship in agricultural systems, it was assumed that the input energy is represented by the attainable crop yield, as predicted through simulation models based on environmental variables. The method of FAO's agroecological zones was applied to the assessment of the attainable sugarcane yield, while Instituto Brasileiro de Geografia e Estatística (IBGE) data were used as observed yield. Sugarcane efficiency production in São Paulo state was evaluated in two growing seasons, and its correlation with some physical factors that regulate production was calculated. A strong relationship was identified between crop production efficiency and soil aptitude. This allowed inferring the effect of agribusiness factors on crop production efficiency. The relationships between production efficiency and climatic variables were also quantified and indicated that solar radiation, annual rainfall, water deficiency, and maximum air temperature are the main factors affecting the sugarcane production efficiency.

Disponibilitat per a les plantes de Mn, Cu, Zn i Cd en els sòls de diferents sistemes agrícoles a Catalunya

Es va avaluar el contingut del sòl en Mn, Cu, Zn, Ni i Cd fent una extracció amb DTPA, segons el mètode de Lindsay i Norvell (1969). Les mostres analitzades procedien de parcel·les agrícoles d'arreu de Catalunya, conservades al Banc de Mostres de Sòls del Mapa de Sòls de Catalunya del DARP. Els resultats es van agrupar per sistemes agrícoles en funció de l'origen de les mostres, ja que dins de cada un es pot assumir una reducció important en l'interval de variació de diferents factors. Es va realitzar una comparació estadística entre els valors mitjans dels diferents sistemes agrícoles, entre els valors mitjans de les dues profunditats de sòl considerades, i una interpretació agronòmica. Els resultats van indicar que els sòls procedents d'horticultura intensiva del Maresme són els que tenen continguts disponibles més elevats dels metalls considerats. D'altra banda, es fa palès que els valors estan condicionats tant pel material originari del sòl com per l'acció antròpica. Per al Cu i el Zn en les mostres de sòls del Maresme els continguts trobats estan molt per sobre dels mínims considerats com a agronòmicament satisfactoris.

Sistemas agrarios sustentables y transiciones en el metabolismo agrario: desigualdad social, cambios institucionales y transformaciones del paisaje en Catalunya (1850-2010)

How did farmers maintain soil fertility as they cultivated the same land over decades and centuries? How did they transfer energy and nutrients (nitrogen, potassium, phosphorous) across the landscape to fertilize crops? How did farmers structure landscapes (field, pasture, woodland) to sustain communities, ensure long-term productivity, and produce profits? We summarize in this article the results of the ongoing research on the last stage of organic agriculture in Catalonia carried out by our project. We also outline the forthcoming steps to continue our research.

Fertilizing Methods and Nutrient Balance at the End of Traditional Organic Agriculture in the Mediterranean Bioregion: Catalonia (Spain) in the 1860s

By reconstructing the nutrient balance of a Catalan v illage circa 1861-65 we examine the sustainability of organic agricultural sy stems in the northwest Mediterranean bioregion prior to the green rev olution and the question of whether the nutrients extracted f rom the soil were replenished. With a population density of 59 inhabitants per square km, similar to other northern European rural areas at that time, and a lower liv estock density per cropland unit, this v illage experienced a manure shortage. The gap was f illed by other labour-intensiv e way s of transf erring nutrients f rom uncultiv ated areas into the cropland. Key elements in this agricultural sy stem were v iney ards because they hav e f ew nutrient requirements, and woodland and scrublands as sources of relev ant amounts of nutrients collected in sev eral ways.

Yield in double cropping system as affected by N fertilization rate with pig slurry in a Catalonia dryland region

Intensive swine production is an important agricultural and economical activity in Europe. The high availability of pig slurry (PS) lead to attractive fertilization strategy to reduce costs, therefore is mainly applied as fertilizer in agricultural systems. The optimization N fertilization in these areas should be taken in into to avoid nitrates losses by lixiviation and to achieve maximum efficiency in crop nutrition. Many studies have shown that PS applications can achieve satisfactory yields in different crops by partially or completely replacing synthetic fertilizers. In addition, for the last years, in Northeast Spain (Catalonia) has been widely extended the double-cropping forage system.

Simulation of moisture profiles in a Latossol in Dourados region, in the State of Mato Grosso do Sul, Brazil

The understanding of unsaturated soil water flow at process-level is essential to develop proper management actions for environmental protection in agricultural systems. One important tool for simulation of soil water flow that has been used worldwide is the SWAP model. The aim of this work was to test and to calibrate the SWAP model by inverse modeling to describe moisture profiles in a Brazilian very clayey Latossol in Dourados, State of Mato Grosso do Sul, Brazil. The SWAP model was tested in an experimental field of 0.09 ha cultivated with soybean and soil profiles were sampled eight times between December 2006 and October 2007. The SWAP input values (i.e. soil water retention curves and meteorological data) were based on in-situ measurements. Simulations with uncalibrated soil water retention curves resulted in moisture profiles that were too wet for almost all sampling dates, in particular between 0-10 cm depth. After calibration of soil water retention curves, there was a good improvement in the simulated moisture profiles, which were within the range of measured values for almost all depths and sampling dates.