Nitrogen use efficiency for wheat

Nitrogen use efficiency for wheat in semiarid region of Buenos Aires (Argentina): effects of the dose and timing application 

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Martínez, J.M.; J.A. Galantini; M.R. Landriscini. 2015. Eficiencia en el uso del nitrógeno del trigo en la región semiárida de Buenos Aires (Argentina): efectos de la dosis y momento de aplicación. Agriscientia 32 (1): 15-27 

In semiarid regions optimal fertilization is difficult due to erratic rainfall. The aim of this study was to analyze the influence of climate variability on the response to different rates and timing of fertilization on wheat productivity and on efficiencies in the use of nitrogen in a site of the semiarid region of the province of Buenos Aires, Argentina. For five years, fertilization trials were conducted in wheat combining N rates (0, 25, 50 y 100 kg ha^-1) and times of fertilization: Seeding (Ns) and tillering (Nm). Agronomic efficiency (EUF) for dry matter (MS) and grain, and apparent recovery of nitrogen (RAN) were evaluated. Interactions between variables (year, rates and times) and efficiencies were found. In Nm, significant correlations of all parameters were found with October rainfall. Protein for Ns and Nm was significantly and inversely correlated with full cycle rainfall. Significant correlations were found in EUF of MS and grain in this order: Full cycle rainfall> Spring rainfall> Oct rainfall> Set rainfall. Interannual climate variability showed the greatest influence on the nitrogen use efficiencies, regardless the application timing.

Dr. Juan Manuel Martínez, CERZOS (CONICET-UNS) y Departamento de Agronomía UNS, jmmartinez@criba.edu.ar

Dr. Juan Alberto Galantini, Comisión de Investigaciones Científicas (CIC, BA), CERZOS-(CONICET-UNS), Dpto. Agronomía (UNS). Bahía Blanca, Argentina. jgalanti@criba.edu.ar

M.Sc. María Rosa Landriscini, CERZOS (CONICET-UNS), Dpto. Agronomía Universidad Nacional del Sur. mlandris@criba.edu.ar

Foliar Nitrogen fertilization of wheat in Southwestern Buenos Aires

Foliar nitrogen fertilization of wheat in Southwestern Buenos Aires

M.R. Landriscini, J.M. Martínez, J.A. Galantini

Abstract

In the semiarid and subhumid Pampean region, foliar nitrogen (N) application to wheat at anthesis stage coincides with an erratic rainfall period, which defines yield and quality. The objectivesof the study were to evaluate the effect of foliar N application at anthesis on wheat grain yield and quality in the Southwestern of Buenos Aires Province, an area characterized by variations in climate and soil fertility, and to apply the principal component analysis (ACP) in all variables. A total of 30 experiments were conducted from 2004 to 2012 in the Southwestern. Nitrogen rates of 0, 25, 50 and 100 kg N ha^-1were applied at sowing and 25 kg ha^-1 at anthesis. Water availability to the crop was variable in the study period, which caused significant yield variations. The ANOVA for all the experiments, showed no significant differences for N at sowing or at anthesis, but it indicated a protein increase in 25 of the 30 experiments. In all trials yield from the control treatment ranged from 1784 to 2600 kg ha^-1and N foliar application response from 145 to 1273 kg ha^-1. The grain protein content, which averaged 132 g kg^-1, increased 11% with N fertilization at anthesis. Low and poorly distributed rainfall limited yield and foliar N response. Nitrogen rates at sowing that produced the maximum response to foliar application ranged from 0 to 100 kg N ha^-1. The most influential variables in ACP were the rainfall of September, October and November, dry matter at Z60,soil water content at sowing and N availability. The yield was estimated with 72 % confidence and protein with 59%. In these environments, foliar N application resulted in variable grain yield buy it proved to be a useful practice for enhancing protein content.

Key words: Nitrogen, Anthesis, Yield, Grain Quality

In Landriscini M.R., J.M. Martínez, J.A. Galantini. 2015. Fertilización foliar con nitrógeno en trigo en el sudoeste bonaerense. Ciencia del Suelo (In press)

Texture influence on soil phosphorus content and distribution in semiarid Pampean grasslands

Soil texture can modify the content and dynamic of soil phosphorus (P). The objective of this work was to study the P form contents associated to physical fractionation of SOM in soils with different texture. Soil samples (0-0.15 m) were obtained from 27 sites with different texture in a twenty five years old pasture located in the Experimental Station of Bordenave, Argentina (63°01’20”W; 37°51’55”S). Soil particle size fractions were obtained by wet sieving separating the fine (0-100 µm) and coarse (100-2000 µm) fractions. Soil organic matter was determined in each fraction, mineral associated (MOM) and particulate organic matter (POM), respectively. Extractable (Pe), organic (Po), inorganic (Pi) and total extractable (Pt) phosphorus was determined and occluded P (Pocl) was calculated as the difference [Pt - (Po+Pi)] in the whole soil and the particles fractions. In these soils, texture determines P reserves and the equilibrium of its different forms. Available P forms (estimated by Pe) was related to the inorganic form present the fine fraction of the soil. Phosphorus content in its different forms is closely associated with soil fractions. Soils with higher content of fine fraction present the coarse fraction enriched in Po. All the studied P forms were higher in fine textured soils than in coarse ones, however, P forms in particle size fractions showed different tendencies. In coarse textured soils, Po in MOM was lower than fine textured ones. However, P content in MOM was richer and in POM was poorer than in fine textured soils. The available P, estimated with Pe content, comes predominantly from the inorganic pool and it is associated to the fine fraction of the soil. Phosphorus content in its different forms is closely associated with soil size fractions. It was proposed a conceptual model in which size fractionation of SOM and P forms determination can be represented to a better understanding of soil P equilibriums.

Suñer L., Galantini J.A. 2015. Texture influence on soil phosphorus content and distribution in semiarid Pampean grasslands. International Journal of Plant & Soil Science (ISSN: 2320-7035) Vol.: 7, Issue: 2 109-120, no. IJPSS.2015.136, 

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Long-term effect of continuous wheat on soil organic matter

Continuous wheat in semiarid regions: Long-term effects on stock and quality of soil organic carbon

Continuous wheat (Triticum aestivum L.) cropping in semiarid regions results in variable dry matter production. As a consequence, the balance of soil organic carbon (SOC) may vary over time. The aim of this research was to assess the dynamics and long-term changes of physically and chemically extracted SOC fractions. Soil samples (0-5, 5-10 and 10-20 cm depths) from continuous wheat, with (f) and without (nf) fertilizer (N+P) under conventional- (CT, for 25 y) and no-tillage (NT, for 6 y) were taken during the experiment. Mineral-associated (MOC, 0-0.053 mm), fine particulate (POC_f, 0.053-0.100 mm) and coarse particulate (POC_c, 0.1-2.0 mm) SOC and humic substances were obtained. SOC variability was depending on water availability during fallow periods (SOC decomposition) or crop cycles (dry matter production). The mean wheat yields were 1.33 (nf) and 2.09 (f) Mg grain ha^-1, with an estimated carbon input of 1.64 (nf) and 2.20 (f) Mg C ha^-1 yr^-1. Losses from the initial level were higher in labile fractions, POC_c (-75%) and POC_f (-53%), than in MOC (-15%). Humic acids present slight differences in their structure and quantity as a result of long-term cropping. Conversion from CT to NT resulted in contrasting results. For an equivalent soil mass, fertilizer application increased SOC by 4.31 Mg ha^-1 (under CT) and 7.29 Mg ha^-1 (under NT). The SOC turned out to be higher under NT with fertilizer use and lower without application. No-tillage does not increase SOC content by itself; it must be combined with other agricultural practices, such as fertilization and/or crop rotation.

Keywords: Fertilization, Tillage system, Physical organic carbon fractions, Humic substances

Galantini Juan A., Matias E. Duval, Julio O. Iglesias and Hugo Kruger. 2014. Continuous wheat in semiarid regions: Long-term effects on stock and quality of soil organic carbon. Soil Science 179: 284-292.
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Soil porosity under crop-grazing systems

Soil pore distribution as affected by cattle trampling under no-till and reduced-till systems

Soil pore size affects soil air and water dynamics, and thus influence crop productivity. The aim of this study was to evaluate the impact of reduced-tillage (RT) and no-tillage (NT) systems on soil pore distribution under animal grazing. The soil was sampled at 0-5, 5-10, 10-15 and 15-20 cm depths before and after animal grazing. 

Doctoral Thesis JUAN MANUEL MARTÍNEZ

March 16, 2015-03-20

Doctoral Thesis  JUAN MANUEL MARTÍNEZ

Department of Agronomy, Universidad Nacional del Sur, Bahía Blanca, Argentina

Director Dr. Juan Galantini

Comisión Investigaciones Científicas (CIC), CERZOS (UNS CONICET)

NITROGEN USE AND BALANCE IN WHEAT SYSTEMS AL SO BONAERENSE: SOIL DYNAMIC AND CROP NUTRITION

Optimizing nitrogen fertilization in regions with low and variable rainfall is difficult, because it demand to know the nitrogen (N) dynamics in the soil-plant system under no-tillage (SD). Therefore, the general hypothesis was: the N use efficiency (EUN) varies with water availability and efficiency of fertilization can be improved by knowing N supply of labile organic fractions. The overall aim was to evaluate the EUN in different soil and climatic conditions and estimate the amount and origin of N from the decomposition of soil organic matter. From 2004 to 2012, 18 trials were conducted combining fertilization rates and timing in several fields. Also, during 2010 and 2011 the apparent N mineralization was evaluated in 78 agricultural fields, with more than 10 years under SD with the aim of finding soil mineralization and crop indicators. The importance of the more carbon and N labile fractions on potentially N mineralization, determined in long-term incubations was proved. Carbon of fine particulate fraction (COPf) might be a better index N mineralization than the total particulate organic carbon (COPt). Anaerobic N (Nan) was the most related index to N mineralization; however, the use of rapid indexes with soil parameters improved the prediction of apparent N mineralization. Only higher yields were detected by N at tillering -in semiarid environment- where rainfall year exceeded the historical average. In subhumid environment was not found differential effect with N applied at vegetative stages. The clorophyll meter was a promising indicator of N uptake, however, would not be an accurate tool for predicting the N grain. Furthermore, was found that Spad readings with available N improved the prediction of EUN and physiological efficiency. The SD improved all N organic fractions. Although Nan was not associated with the N uptake at harvest, showed differences between tillage systems, being indicator of potential fertility, not necessarily associated with performance.

Doctoral Thesis MATIAS EZEQUIEL DUVAL

March 16, 2015-03-20

Doctoral Thesis MATIAS EZEQUIEL DUVAL

Department of Agronomy, Univeridad Nacional del Sur, Bahía Blanca, Argentina

Director Dr. Juan Galantini

Comisión Investigaciones Científicas (CIC), CERZOS (UNS CONICET)

CONTENT, QUALITY AND DYNAMIC OF SOIL ORGANIC FRACTIONS AS INDICATORS OF SOIL QUALITY UNDER NO-TILLAGE SYSTEMS

The intensification of agriculture, with a gradual degradation of Argentina’s soil, has increased erosion processes and loss of fertility. The aim of this dissertation was to analyze different soil parameters, either alone or combined, to serve as sensitive indicators in the assessment of different management practices on sites with different climate and soil conditions. The study sites are located in Bengolea and Monte Buey (Córdoba), Pergamino (Buenos Aires) and Viale (Entre Rios). Good agricultural practices, Poor agricultural practices and natural environment (reference) at each site were evaluated. During the period from September 2009 to September 2012 soil sampling was performed in the months of February and September, in which it was determined: total organic carbon (COT), total nitrogen, pH and available phosphorous. A series of physical and chemical methods of fractionation to obtain organic fractions with different characteristics and cycling time was applied. Also a number of physical properties related to the size and distribution of pores, water availability and their relationship to soil management practices were analyzed. COT levels in AN decreased from the East (28 g kg^-1 in Viale) to West (14 g kg^-1 in Bengolea) following the rainfall and texture gradient of sites. Relationships between different labile organic fractions with COT in AN showed differences among sites, reflecting different dynamics according to the characteristics of the environment in different localities. COT levels in 0-20 cm depths of agricultural soils were 6-42% lower than AN where soybean frequency was one of the main factors causing these declines. In general, the labile organic fractions showed differential sensitivity. Those with higher lability (COP_g and CHs) showed differences related to land use, while intermediate lability (COP_f and CHt) were useful to highlight the changes due to agricultural practices. Between agricultural managements, both cropping intensity and crop type in the rotation changed the content and distribution of COT and its fractions. The sensitivity to temporal variations and management was higher in the labile organic fractions that in the COT. In turn, the magnitude of variability was different between fractions, where temporal fluctuations increased in the following order COM < COT < COP_f ≤ CHt < CHs ≤ COP_g. The combination of information from different soil attributes through indices such as COT/clay, stratification index and C pool index allowed a better differentiate the effect of use and management. The physical properties were degraded by agricultural managements with higher values of bulk density, influenced by texture, lower macroporosity and air capacity, without finding a physical indicator to different agricultural practices on all sites.