The effects of crop rotations and fertilization on wheat productivity

 The effects of crop rotations and fertilization on wheat productivity in the pampean semiarid region of Argentina. 1. Soil physical and chemical properties

Wheat in the semiarid region of Argentina has often been grown as a low-input crop. Rainfall scarcity and distribution are the main characteristics of this region. The knowledge of the combined effects of crop rotation and fertilization on soil physical and chemical properties are the key for a sustainable crop production. Soil properties for an Entic Haplustoll in the semiarid region of Argentina were evaluated, where different crop rotations were used for 15 years. Wheat-wheat (Triticum aestivum L.) (WW), wheat-grazing natural grasses (WG) and wheat-legume [vetch (Vicia sativa L.) plus oat (Avena sativa L.) or Triticale (Triticum aestivum L.  Secale cereale L.)] (WL) rotations with and without fertilizer (64 kg N and 16 kg P ha^-1) were studied. The annual wheat cropping system (WW) resulted in the lowest soil organic carbon (SOC) and total nitrogen (Nt) levels. Extractable phosphorus (Pext) values were sufficient for wheat growth with all treatments and decreased with depth. Fertilizer applications significantly increased the proportion of large pores (>8.81 mm) in the 0±0.07 m depth of the WW and WG system plots. A decrease in the proportion of medium size pores (0.19-8.81 mm) and in the water holding capacity was observed in the WG rotation plots. The fertilized treatments resulted in the following sequence of available water: WL > WW > WG. Bulk density was similar with all treatments for each depth, except with the fertilized WG treatment that had the lowest value in the 0-0.07 m depth. These results showed the positive influence of legume inclusion (WL) and alternate cattle grazing (WG) on SOC and Nt contents.

Miglierina A.M., J.O. Iglesias, M.R. Landriscini, J.A. Galantini, R.A. Rosell. 2000. The effects of crop rotations and fertilization on wheat productivity in the pampean semiarid region of Argentina. 1. Soil physical and chemical properties. Soil & Tillage Research 53: 129-135. 

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Nutrient accumulation, balance and partition patterns in different wheat production systems

 

Little research has been done on the accumulation of N, P, K, and S in wheat plants growing under different crop production systems in the Pampean Semiarid Region. Consequently, the effects of wheat-grazing (TP), wheat-wheat (TT), and wheat-clover (TL), with and without fertilizer, production systems on total aerial dry matter (TADM) and N, P, K, and S accumulation at different growth stages were studied. Nutrient plant concentration decreased with the length of the cycle. Phosphorus and sulfur adequate levels were observed along wheat growing season. N deficiencies were observed since booting wheat growth stage. Potassium concentration sharply dropped between 90-140 growing days. Nitrogen, P, K and S uptake (kg ha^-1) gradually increased reaching the highest value at booting. Legume in crop sequences gave highest wheat dry matter, nutrient uptake and grain yield. Fertilizer application increased TADM and grain yield only in TT and TL.

Galantini J.A., M.R. Landriscini, R.A. Rosell. 2000. Patrones de acumulación, balance y partición de nutrientes en diferentes sistemas de producción de trigo. Revista de Investigaciones Agropecuarias (RIA-INTA) 29 (2) 99-110.

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Cover Crops in the Production System

Winter cover crops in soybean monoculture: Effects on soil organic carbon and its fractions

The current agricultural production systems in the Pampas Region have been significantly simplified by cultivating large land areas under no tillage (NT), where soybean is the predominant crop. These systems with long periods of fall-winter fallow and poor annual input of carbon (C) into the soil lead to soil degradation, thereby affecting physical and chemical properties. A 6-year cover crop study was carried out on a Typic Argiudoll under NT in the south of Santa Fe, Argentina. Various winter species were used as cover crops: wheat (W), oat (O), vetch (V), an oat + vetch mixture (O + V) and a control (Ct) treatment without a cover crop. We examined the influence of cover crops on the following soil organic C-fractions: coarse particulate organic carbon (POCc), fine particulate organic carbon (POCf) and mineral-associated organic carbon (MOC) from 2008 to 2011. Aboveground carbon input by the cover crops was related to the June to October rainfalls. In general, the W and O treatments supplied a higher amount of C to the soil; these gramineous species produced 22 and 86% more biomass than O + V and V. The water cost of including cover crops ranged from 13 to 93 mm compared with Ct. However, this water-use did not affect soybean yields. On average, gramineous species (pure stand or mixture) supplied more than 3.0 Mg C ha^-1 year^-1 to the soil, whereas V supplied less than 2.0 Mg C ha^-1 year^-1. Increase in the mean annual C-input by residues into the soil (cover crop + soybean) explained most SOC variation (R² = 0.61; p < 0.05). This relationship was more evident with labile soil organic fractions, both for POCc (R² = 0.91; p < 0.001) and POCc + POCf (R² = 0.81; p < 0.001). The stratification ratios of SOC (SI, 0-5: 10-20 cm) reflected differences among treatments, where >2.0 for W; 1.7 for O, O + V and V, and <1.5 for Ct. Soil physical fractionation by particle size showed that cover crops affected the most dynamic fraction directly associated with residue input (POCc) at 0-5 and 5-10 cm. At 0-5 cm, the effects were observed in the most transformed fractions (MOC and POCf) 4 years after the experiment started, whereas at 0-20 cm, differences in the labile fractions (POCc and POCf) were found at the end of the experiment (6 years). Although C-input by the cover crops fueled decomposition of labile soil organic fractions, concentration of surface SOC and its associated fractions (POCc, POCf and MOC) was modified after 6 years. This effect became noticeable during the third year when the plots under cover crops showed a higher SI than the traditional fallow.

Organic fractions, Carbon balance, carbon stratification index

Duval M., J.A. Galantini, Julia E. Capurro, J.M. Martinez, F.M. López. 2016. Winter cover crops in soybean monoculture: effects on soil organic carbon and its fractions. Soil & Tillage Research 161:95-105 doi:10.1016/j.still.2016.04.006

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Cover Crops in the Production System

Production and quality of cover crops in soybean monoculture

Cover crops (CC) are an alternative to improve soil organic matter, capture labile nutrients and minimizing its leaching losses during long-term fallows, typical of agricultural systems with high frequency soybean (Glycine max L. Merr.). The objective was to evaluate the production and nutrient content of different CC in simplified system (soybean monoculture) under no-tillage. CC used were: (T) bread wheat (Triticum aestivum L.), (A) oat (Avena sativa L.), (V) vetch (Vicia sativa L.) and (A+V) oat + vetch. Upon drying the CC was determined: production of total aerial dry matter (MS), biochemical composition (cellulose, hemicellulose and lignin), macro- and micronutrients. Dry matter production in T and A ranged between 7.2 and 11.1 Mg ha^-1, differing significantly from V with values between 4.1 and 4.6 Mg ha^-1. Carbon concentration did not differ between CC (43-45% C). The amount of N accumulated in aboveground biomass ranged between 102 and 212 kg N ha^-1, showing differences only between years. The concentration of structural polymers clearly differ between CC species, where T and A showed higher concentrations of cellulose and hemicellulose regarding V. Conversely, V showed higher concentrations of nonstructural carbohydrates and lignin than grasses. Winter grasses as CC were more efficient in producing MS and therefore more effectives to contribute to increased soil organic matter, promoting the recycling of macro- and micronutrients, preventing the leaching of those most labile.

Wheat-vetch, Biochemical composition

Duval, Matías E.; Galantini, Juan A.; Capurro, Julia E.; Beltrán, Marcelo J. 2017. Producción y calidad de diferentes cultivos de cobertura en monocultivo de soja. Ciencias Agronómicas (FCA-UNR) XXIX 7-13.
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Soil organic matter quality, quantity and distribution under different tillage systems

Galantini, J.A.; M. Duval; J.M. Martinez; V. Mora; R. Baigorri & J.M. García-Mina. 2016. Quality and quantity of organic fractions as affected by soil depth in an argiudoll under till and no-till systems. International Journal of Plant & Soil Science 10 (5) - doi:10.9734/IJPSS/2016/25205

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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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