Multivariate analysis applied to the study of the relationship between soil and plant properties in a peach orchard

In the State of Rio Grande do Sul, the municipality of Pelotas is responsible for 90 % of peach production due to its suitable climate and soil conditions. However, there is the need for new studies that aim at improved fruit quality and increased yield. The aim of this study was to evaluate the relationship that exists between soil physical properties and properties in the peach plant in the years 2010 and 2011 by the technique of multivariate canonical correlation. The experiment was conducted in a peach orchard located in the municipality of Morro Redondo, RS, Brazil, where an experimental grid of 101 plants was established. In a trench dug beside each one of the 101 plants, soil samples were collected to determine silt, clay, and sand contents, soil density, total porosity, macroporosity, microporosity, and volumetric water content in the 0.00-0.10 and 0.10-0.20 m layers, as well as the depth of the A horizon. In each plant and in each year, the following properties were assessed: trunk diameter, fruit size and number of fruits per plant, average weight of the fruit per plant, fruit pulp firmness, Brix content, and yield from the orchard. Exploratory analysis of the data was undertaken by descriptive statistics, and the relationships between the physical properties of the soil and of the plant were assessed by canonical correlation analysis. The results showed that the clay and microporosity variables were those that exhibited the highest coefficients of canonical cross-loading with the plant properties in the soil layers assessed, and that the variable of mean weight of the fruit per plant was that which had the highest coefficients of canonical loading within the plant group for the two years assessed.

Changes in Soil Organic Carbon Fractions in Response to Cover Crops in an Orange Orchard

ABSTRACT The cultivation of cover crops intercropped with fruit trees is an alternative to maintain mulch cover between plant rows and increase soil organic carbon (C) stocks. The objective of this study was to evaluate changes in soil total organic C content and labile organic matter fractions in response to cover crop cultivation in an orange orchard. The experiment was performed in the state of Bahia, in a citrus orchard with cultivar ‘Pera’ orange (Citrus sinensis) at a spacing of 6 × 4 m. A randomized complete block design with three replications was used. The following species were used as cover crops: Brachiaria (Brachiaria decumbes) – BRAQ, pearl millet (Pennisetum glaucum) – MIL, jack bean (Canavalia ensiformis) – JB, blend (50 % each) of jack bean + millet (JB/MIL), and spontaneous vegetation (SPV). The cover crops were broadcast-seeded between the rows of orange trees and mechanically mowed after flowering. Soil sampling at depths of 0.00-0.10, 0.10-0.20, and 0.20-0.40 m was performed in small soil trenches. The total soil organic C (SOC) content, light fraction (LF), and the particulate organic C (POC), and oxidizable organic C fractions were estimated. Total soil organic C content was not significantly changed by the cover crops, indicating low sensitivity in reacting to recent changes in soil organic matter due to management practices. Grasses enabled a greater accumulation of SOC stocks in 0.00-0.40 m compared to all other treatments. Jack bean cultivation increased LF and the most labile oxidizable organic C fraction (F1) in the soil surface and the deepest layer tested. Cover crop cultivation increased labile C in the 0.00-0.10 m layer, which can enhance soil microbial activity and nutrient absorption by the citrus trees. The fractions LF and F1 may be suitable indicators for monitoring changes in soil organic matter content due to changes in soil management practices.

Tomato yield and potassium concentrations in soil and in plant petioles as affected by potassium fertirrigation

Tomato (Lycopersicon esculentum Mill.) cv. Santa Clara was grown on a silt clay soil with 46 mg dm-3 Mehlich 1 extractable K, to evaluate the effects of trickle-applied K rates on fruit yield and to establish K critical concentrations in soil and in plant petioles. Six potassium rates (0, 48, 119, 189, 259 and 400 kg ha-1 K) were applied in a randomized complete block design with four replications. Soil and plant K critical levels were determined at two plant growth stages (at the beginning of the second and fourth cluster flowering). Total, marketable and weighted yields increased with K rates, reaching their maximum of 86.4, 73.4, and 54.9 ton ha-1 at 198, 194, and 125 kg ha-1 K , respectively. At the first soil sampling date K critical concentrations in the soil associated with K rates for maximum marketable and weighted yields were 92 and 68 mg dm-3, respectively. Potassium critical concentrations in the dry matter of the petioles sampled by the beginning of the second and fourth cluster flowering time, associated with maximum weighted yield, were 10.30 and 7.30 dag kg-1, respectively.

Influence of soil properties on the abundance of plant species in ferruginous rocky soils vegetation, southeastern Brazil

Ferruginous "campos rupestres" are a particular type of vegetation growing on iron-rich primary soils. We investigated the influence of soil properties on plant species abundance at two sites of ferruginous "campos rupestres" and one site of quartzitic "campo rupestre", all of them in "Quadrilátero Ferrífero", in Minas Gerais State, southeastern Brazil. In each site, 30 quadrats were sampled to assess plant species composition and abundance, and soil samples were taken to perform chemical and physical analyses. The analyzed soils are strongly acidic and presented low fertility and high levels of metallic cations; a principal component analysis of soil data showed a clear segregation among sites due mainly to fertility and heavy metals content, especially Cu, Zn, and Pb. The canonical correspondence analysis indicated a strong correlation between plant species abundance and soil properties, also segregating the sites.

Molecular biodiversity of microbial communities in polluted soils and their role in soil phytoremediation

Les métaux lourds (ML) s’accumulent de plus en plus dans les sols à l’échelle mondiale, d’une part à cause des engrais minéraux et divers produits chimiques utilisés en agriculture intensive, et d’autre part à cause des activités industrielles. Toutes ces activités génèrent des déchets toxiques qui s’accumulent dans l’environnement. Les ML ne sont pas biodégradables et leur accumulation cause donc des problèmes de toxicité des sols et affecte la biodiversité des microorganismes qui y vivent. La fertilisation en azote (N) est une pratique courante en agriculture à grande échelle qui permet d’augmenter la fertilité des sols et la productivité des cultures. Cependant, son utilisation à long terme cause plusieurs effets néfastes pour l'environnement. Par exemple, elle augmente la quantité des ML dans les sols, les nappes phréatiques et les plantes. En outre, ces effets néfastes réduisent et changent considérablement la biodiversité des écosystèmes terrestres. La structure des communautés des champignons mycorhiziens à arbuscules (CMA) a été étudiée dans des sols contaminés par des ML issus de la fertilisation à long terme en N. Le rôle des différentes espèces de CMA dans l'absorption et la séquestration des ML a été aussi investigué. Dans une première expérience, la structure des communautés de CMA a été analysée à partir d’échantillons de sols de sites contaminés par des ML et de sites témoins non-contaminés. Nous avons constaté que la diversité des CMA indigènes a été plus faible dans les sols et les racines des plantes récoltées à partir de sites contaminés par rapport aux sites noncontaminés. Nous avons également constaté que la structure de la communauté d'AMF a été modifiée par la présence des ML dans les sols. Certains ribotypes des CMA ont été plus souvent associés aux sites contaminés, alors que d’autres ribotypes ont été associés aux sites non-contaminés. Cependant, certains ribotypes ont été observés aussi bien dans les sols pollués que non-pollués. Dans une deuxième expérience, les effets de la fertilisation organique et minérale (N) sur les différentes structures des communautés des CMA ont été étudiés. La variation de la structure de la communauté de CMA colonisant les racines a été analysée en fonction du type de fertilisation. Certains ribotypes de CMA étaient associés à la fertilisation organique et d'autres à la fertilisation minérale. En revanche, la fertilisation minérale a réduit le nombre de ribotypes de CMA alors que la fertilisation organique l’a augmenté. Dans cette expérience, j’ai démontré que le changement de structure des communautés de CMA colonisant des racines a eu un effet significatif sur la productivité des plantes. Dans une troisième expérience, le rôle de deux espèces de CMA (Glomus irregulare et G. mosseae) dans l'absorption du cadmium (Cd) par des plants de tournesol cultivés dans des sols amendés avec trois niveaux différents de Cd a été évalué. J’ai démontré que les deux espèces de CMA affectent différemment l’absorption ou la séquestration de ce ML par les plants de tournesol. Cette expérience a permis de mieux comprendre le rôle potentiel des CMA dans l'absorption des ML selon la concentration de cadmium dans le sol et les espèces de CMA. Mes recherches de doctorat démontrent donc que la fertilisation en N affecte la structure des communautés des CMA dans les racines et le sol. Le changement de structure de la communauté de CMA colonisant les racines affecte de manière significative la productivité des plantes. J’ai aussi démontré que, sous nos conditions expériemntales, l’espèce de CMA G. irregulare a été observée dans tous les sites (pollués et non-pollués), tandis que le G. mosseae n’a été observé en abondance que dans les sites contaminés. Par conséquent, j’ai étudié le rôle de ces deux espèces (G. irregulare et G. mosseae) dans l'absorption du Cd par le tournesol cultivé dans des sols amendés avec trois différents niveaux de Cd en serre. Les résultats indiquent que les espèces de CMA ont un potentiel différent pour atténuer la toxicité des ML dans les plantes hôtes, selon le niveau de concentration en Cd. En conclusion, mes travaux suggèrent que le G. irregulare est une espèce potentiellement importante pour la phytoextration du Cd, alors que le G. mosseae pourrait être une espèce appropriée pour phytostabilisation du Cd et du Zn.

Effects of diverse plant species on the bioavailability of contaminants in soil

La phytoremédiation constitue une technologie alternative pour le traitement de sols contaminés en métaux. Toutefois, la biodisponibilité des métaux dans le sol peut limiter l’efficacité de cette approche. Nous émettons l’hypothèse que diverses espèces de plante, caractérisées par systèmes racinaires différents, peuvent affecter différemment la biodisponibilité des éléments traces (ET) dans le sol. Une étude utilisant un dispositif expérimental en bloc aléatoire complet avec cinq réplicats a été conduite entre le 6 juin et le 3 septembre 2014, sur le site du Jardin botanique de Montréal. Dans ce contexte, l’impact de la présence de huit espèces de plantes, herbacées ou ligneuses, sur le pool labile de six métaux (Ag, Cu, Pd, Zn, Ni et Se) dans la rhizosphère de celles-ci a été étudié. Après trois mois de culture, la biomasse aérienne et souterraine de chaque espèce a été mesurée et la concentration en ET dans les tissus des plantes a été analysée. La fraction labile de ces ET dans la rhizosphère (potentiellement celle qui serait biodisponible) de même que d’autres paramètres édaphiques (le pH, la conductivité, le pourcentage de matière organique et le carbone organique dissous (COD)) ont aussi été mesurés et comparés en fonction de la présence d’une ou l’autre des espèces utilisées. Les résultats montrent que pour la plupart des plantes testées, les plus fortes concentrations en ET ont été trouvées dans les racines alors que les plus faibles niveaux s’observaient dans les parties aériennes, sauf pour le Ni dans le Salix nigra. Ceci suggère que le Ni peut être extrait du sol par des récoltes régulières des tiges et des feuilles de cette espèce de saule. Les pools labiles de l’Ag, Ni et du Cu dans la rhizosphère étaient significativement et différemment affectés par la présence des plantes. Toutefois, la présence des plantes testées n’a pas affecté certains paramètres clés de la rhizosphère (ex. le pH, conductivité, et le pourcentage de matière organique). À l’opposé, les niveaux de COD dans la rhizosphère de toutes les plantes testées se sont révélés supérieurs en comparaison des témoins (sols non plantés). De plus, une corrélation positive a pu être établie entre la concentration disponible du Ni et la concentration en COD. Une relation similaire a été déterminée pour le Cu. Ceci suggère que certains systèmes racinaires pourraient modifier les niveaux de COD et avoir un impact indirect sur les pools labiles des ET dans le sol.

Effectiveness of coir geotextiles in soil moisture conservation

Among the diversified use of coir geotextiles, its use as a protective covering to improve crop productivity and to reduce weed problem assumes to be much significant. An experiment has been conducted at Kumbazha, in Pathanamthitta district, Kerala, India to evaluate the different types of coir geotextiles and polythene as soil mulch. The treatments include different mulching materials like natural needled felt, black needled felt, rubberized coir, black polythene and transparent polythene along with a control plot (no mulch). The experiment was laid out in Completely Randomized Design with six replications. The test crops used were bhindi (var. Salkeerthi) and pineapple (var. Mauritius). The study reveals that with bhindi crop growth parameters like plant height, leaf number and lateral spread were increased by mulching with rubberized coir and transparent polythene. These two mulches caused early flowering and increased fruit yield. Coir materials as mulch recorded a yield increase ranging from 67 to 196%. Observations also reveal that weeds were not grown in plots mulched with black polythene, transparent polythene and rubberized coir. Rubberized coir as mulch enhanced the fruit yield in the case of pineapple, which is followed by natural needled felt and transparent polythene. Black polythene resisted weed growth up to 7MAP, whereas rubberized coir and transparent polythene suppressed weeds up to 8MAP. Though the weeds were grown in other treatments the weeds count was significantly lower than that of control plot. Mulching with transparent polythene enhanced the soil temperature whereas rubberized coir lowered soil temperature. More over all mulched treatments had a favourable influence in increasing soil moisture. Observing the biodegradability and eco-friendly nature of coir it could be inferred that rubberized coir can serve as good mulch for bhindi and pineapple with minimum weed problem

The development and contribution of surface charge by crop residues in two Malawian acid soils

The effects of maize and soya bean residues on the pH and charge of a loamy sand (Kawalazi) and a sandy clay loam (Naming'omba) from Malawi were measured to determine both the indirect effect of the residues on soil charge through the changes in pH, and the direct contribution of charge carried on the residue surfaces. The soils had pH values (10 mM CaCl2) of 4.3 and 5.0 and organic matter contents were 1.4% and 2.7%, respectively. The clay fractions were dominated by kaolinite and goethite, and mica was present in both samples. The soils were incubated for 28 days with maize (Zea mays) and soya bean (Glycine max) residues. The maximum addition of residue (12.0%) in the Kawalazi and Naming'omba soils increased the pH from 4.3 and 5.0 to 4.8 and 5.3 (maize) and to 9.0 and 8.8 (soya bean), respectively. Negative charge increased from 2.1 and 4.7 cmol(c) kg(-1) to 3.8 and 7.5 (maize) and to 5.3 and 9.3 cmol(c) kg(-1) (soya bean). Positive charge increased from 0.72 and 0.62 to 0.87 and 0.85 cmol(c) kg(-1) (maize) and to 0.75 and 0.68 (soya bean). The charge contribution by the residues was calculated by difference between the charge on a sample incubated with residue and the charge on a soil without residue limed to the same pH value. Up to 100 cmolc negative charge and 10 cmol(c) of positive charge per kg of residue were directly contributed to the soil-residue mixture, the amounts depending on the type of residue, the extent to which the residue was decomposed in the soil and the pH of the mixture. The Anderson and Sposito method [Soil Sci. Soc. Am. J. 55 (1991) 1569] was used to partition the permanent negative charge (holding Cs+) from variable negative charge (holding Li+). In the pH range 3.7-6.5 the maize residue contributed between 3 and 26 cmol(c) of variable charge per kg of residue in the Kawalazi soil and between 6 and 25 cmol(c) per kg of residue in the Naming'omba soil. For soya bean the values were between I and 28 and between 4 and 68 cmolc per kg of residue, respectively. At a given pH value, the charge tended to increase with time of incubation and for a given addition of residue, pH decreased during incubation. Addition of residues contributed no permanent negative charge and the charge on the soil measured by Cs adsorption was independent of pH change caused by the residue showing that the method is valid for soil-residue mixtures. With time there was a decrease in the amount of permanent charge probably due to masking as humic material become adsorbed on mineral surfaces. (C) 2003 Elsevier Science B.V. All rights reserved.

Abiotic drivers and plant traits explain landscape-scale patterns in soil microbial communities

The controls on aboveground community composition and diversity have been extensively studied, but our understanding of the drivers of belowground microbial communities is relatively lacking, despite their importance for ecosystem functioning. In this study, we fitted statistical models to explain landscape-scale variation in soil microbial community composition using data from 180 sites covering a broad range of grassland types, soil and climatic conditions in England. We found that variation in soil microbial communities was explained by abiotic factors like climate, pH and soil properties. Biotic factors, namely community- weighted means (CWM) of plant functional traits, also explained variation in soil microbial communities. In particular, more bacterial-dominated microbial communities were associated with exploitative plant traits versus fungal-dominated communities with resource-conservative traits, showing that plant functional traits and soil microbial communities are closely related at the landscape scale.

The influence of plant species number on productivity, ground coverage and floral performance in grass-free lawns

The grass-free lawn is a novel development in modern ornamental horticulture where the traditional monoculture of grass is replaced by a variety of mowing-tolerant clonal forbs. It brings floral aesthetics and a diverse species approach to the use of lawn space. How the number of constituent forb species affects the aesthetic and structural performance of grass-free lawns was investigated using grass-free lawns composed of four, six and twelve British native clonal perennial forb species. Lawn productivity was seen to increase with increasing species number but the relationship was not linear. Plant cover was dynamic in all lawn types, varied between years and was not representative of individual species' floral performance. The behaviour of component species common to all lawns suggested that lawns with 12 species show greater structural stability than the lawns with a lower species number. Visual performance in lawns with the greatest species number was lower than in lawns with fewer species, with increasing variety in floral size and individual species floral productivity leading to a trade-off between diversity and floral performance. Individual species were seen to have different aesthetic functions in grass-free lawns either by providing flowers, ground coverage or both.

Heavy metal nutrients in tomato plants cultivated in soil amended with biosolid composts

The use of biosolids in horticulture could contribute to recycle residues produced by men. This study analyzed concentrations of Cu, Mn and Zn in the compost during fermentation, in the soil amended with the composts and in the tomato plant materials. Five composts were produced using sugar-cane bagasse, biosolid and cattle manure in the proportions: 75-0-25; 75-12.5-12.5; 75-25-0; 50-50- 0 and 0-100-0 (composts with 0; 12.5; 25; 50 and 100% biosolid), respectively. These composts were used in an experiment with 6 treatments (the 5 composts and a control with mineral fertilization) in a design of randomized blocks with a split plot design. The control and the treatment of 0% biosolid received inorganic nitrogen. All the treatments received the same amount of N, P and K. Two tomato plants were cultivated in each 24 L pot, in a greenhouse at the Technology Department of the Faculdade de Ciências Agrárias e Veterinárias of the Universidade Estadual Paulista in Jaboticabal County, São Paulo State, Brazil. The concentrations of Cu, Mn and Zn were evaluated in the compost 7, 27, 57, 97 and 127 days after composting began, in the soil 0 and 164 days after the compost applied, and in the plants. Compost, soil and plant samples were subjected to digestion with HNO3, H 2O2 and HCl and the metals were determined by AAS. There were positive and significant correlations between Mn in the compost and Mn uptake by the plant (0.46 p>0.05), and between Zn in the compost and Zn concentration in the plant (0.78 p>0.05). Cu, Mn and Zn concentrations increased during composting. The biosolid in the compost supplied Cu and Zn to tomato plants, and the cattle manure supplied Mn to the plants.

Plant nutrients in a degraded soil treated with water treatment sludge and cultivated with grasses and leguminous plants

The objective of this work was to evaluate rates for applications of water treatment sludge (WTS) as a nutrient source for grasses and leguminous plants cropped in a soil degraded by tin mining in the Amazon Region (Natural Forest of Jamari, Rondonia State, Brazil). The treatments consisted of three rates of nitrogen supplied by WTS (100, 150 and 200 mg kg -1 soil), five combinations of plants, two controls (absolute control, without fertilization; and chemical control, soil+lime+chemical fertilizers). WTS modified the contents of macro and micronutrients in the degraded soil, but it was not, as used in the present study, sufficient for the rehabilitation of the degraded area. © 2006 Elsevier Ltd. All rights reserved.

Phosphorus and potassium budget in the soil-plant system in crop rotations under no-till

Soil management and crop rotations can affect P and K budget in soil, decreasing losses, and increasing fertilizer use efficiency. The P and K budget in the soil-plant system at depths up to 60. cm was studied for different soil managements and crop rotations under no-till for three years in Botucatu, São Paulo, Brazil. The investigated crop rotations were: triticale (X Triticosecale) and sunflower (Helianthus annuus) cropped in autumn-winter; pearl millet (Pennisetum glaucum), forage sorghum (Sorghum bicolor), and Sunn hemp (Crotalaria juncea) were grown in the spring, as well as an additional treatment with chiseling followed by a fallow period; and soybean (Glycini max, L., Merril) was cropped in the summer. Each year triticale and sunflower were grown in plots and pearl millet, forage sorghum, Sunn hemp and of chisel/fallow in sub-plots. The triticale/millet rotation led to the largest decrease in available P within the 0-0.60. m layer of the soil profile and the largest K increase within the 0-0.05. m layer. Potassium mobility in the soil profile and the increases in the available K content in the 0.40-0.60. m layer were independent of the management system. Crop rotations with or without chiseling are not effective in preventing soil P losses. There is considerable K leaching below 0.60. m, but chiseling and the use of high K accumulating plants as triticale results in lower K losses. © 2012 Elsevier B.V.

PHOSPHITE AS PHOSPHORUS SOURCE TO GRAIN YIELD OF COMMON BEAN PLANTS GROWN IN SOILS UNDER LOW OR ADEQUATE PHOSPHATE AVAILABILITY

The effects of foliar and soil applied phosphite on grain yield in common bean (Phaseolus vulgaris L.) grown in a weathered soil under low and adequate phosphate availability were evaluated. In the first experiment, treatments were composed of a 2 x 7 + 2 factorial scheme, with 2 soil P levels supplied as phosphate (40 e 200 mg P dm(-3) soil), 7 soil P levels supplied as phosphite (0-100 mg P dm(-3) soil), and 2 additional treatments (without P supply in soil, and all P supplied as phosphite). In the second experiment, treatments were composed of a 2 x 3 x 2 factorial scheme, with 2 soil phosphate levels (40 e 200 mg P dm(-3) soil), combined with 3 nutrient sources applied via foliar sprays (potassium phosphite, potassium phosphate, and potassium chloride as a control), and 2 foliar application numbers (single and two application). Additional treatments showed that phosphite is not P source for common bean nutrition. Phosphite supply in soil increased the P content in shoot (at full physiological maturity stage) and grains, but at the same time considerably decreased grain yield, regardless of the soil phosphate availability. Foliar sprays of phosphite decreased grain yield in plants grown under low soil phosphate availability, but no effect was observed in plants grown under adequate soil phosphate availability. In general, foliar sprays of phosphate did not satisfactorily improve grain yield of the common bean plants grown under low soil phosphate availability.

Long-term decomposition of sugarcane harvest residues in Sao Paulo state, Brazil

Crop residues returned to the soil are important to preserve fertility and sustainability. This research addressed the long-term decomposition of sugarcane post-harvest residues (trash) under reduced tillage, therefore field renewal was performed with herbicide followed by subsoiling and ratoons were deprived of interrow scarification. The trial was conducted in the northern Sao Paulo State, Brazil during four consecutive crops (2005-2008) where litter bags containing N-15-labeled trash were disposed in the field attempting to simulate two distinct situations: the previous crop trash (PCT) or residues incorporated in the field after tillage, and post-harvest trash (PHT) or the remains of plant-cane harvest. Decomposition rates regarding dry matter (DM), carbon (C), root growth, plant nutrients (N, P, K, Ca, Mg and S), lignin (LIG) cellulose (CEL) and hemicellulose (HCEL) contents were assessed for PCT (2005 ndash;2008) and for PHT (2006-2008). There were significant reductions on DM and C:N ratio due to C losses and root growth within the litter bags over time. The DM from PCT and PHT decreased 96% and 73% after four and three crops, respectively, and the higher nutrients release were found for K, Ca and N. The LIG, CEL and HCEL concentrations in PCT decreased 60%, 29%, 70% after four crops and 47%, 35%, 70% from PHT after three crops, respectively. Trash decomposition was driven mainly by residues biochemical composition, root growth within the trash blanket and the climatic conditions during the crop cycles. (C) 2012 Elsevier Ltd. All rights reserved.