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Soil compaction is one of the most relevant crop yield‐limiting factors in no‐till (NT) farming systems in southern Brazil. This study aimed to identify strategies to mitigate soil compaction and increase crop productivity at low, medium and high yield environments within a field. Treatments evaluated were: control (without intervention), PG (phosphogypsum), MC (mechanical chiselling), PCC (polyculture of cover crops), MC + PG, PCC + PG, MC + PCC and MC + PCC + PG. Soil physical and chemical attributes (soil macroporosity, bulk density, penetration resistance) and soybean yield (Glycine max L.) and black oat (Avena strigosa Schreb) biomass production were evaluated. In the low and medium yield environments, MC + PCC + PG promoted the highest soybean yields: 5,455 kg ha−1 and 5,534 kg ha−1, respectively. In the high yield environment, PCC + PG promoted the highest soybean yield (5,579 kg ha−1), whereas MC decreased yields relative to the control. Black oat biomass production responded to the treatments similarly to soybean yields. Overall, integrating two or three decompaction strategies improved soil physical attributes in a greater proportion relative to single strategies and to the control, enhancing both soybean and black oat performances. Selection of the right decompaction strategies for each yield environment might help increase productivity under NT and optimize the use of time, labour, fuel and other resources. Highlights: Soil compaction limits crop yields under no‐tillage farming in southern Brazil.Low, medium and high yield environments were delineated with precision agriculture tools.Single or integrated mechanical, chemical and biological soil decompaction strategies were tested.Soil decompaction strategies to increase soybean yields are specific to yield environments. [ABSTRACT FROM AUTHOR]

Understanding the relationship of corn (Zea mays L.) yield responses to plant density and nitrogen (N) fertilization is critical to production decisions. The main objectives of this study were to (i) evaluate yield responses to plant density and fertilizer N rate at varying yields adjusting models considering a spatial component, (ii) perform a validation for the fitted models with an independent dataset, and (iii) identify key statistical parameters for the yield data distribution governing response models. Analyses were conducted with information from seven fields with 21 studies (one study per yield environment, with three environments per field) conducted from 2009 to 2017 in southern Brazil with geospatial data collected to evaluate yield response to plant density and fertilizer N rates (28911 data points) and one additional database with 12 field studies conducted from 2012 to 2015 in the US Midwest (1773 data points). Databases were divided into training and validation datasets. Field experiments evaluating both plant density and N rate were selected as training dataset. Key research findings were (i) yield-factor response models were dependent on yield environment and within a yield environment those models remained constant regardless the year, country, and hybrid for all evaluated fields, (ii) statistical models considering spatial correlation of the random errors outperformed those considering errors independent and identically distributed and, (iii) yield distribution with comparable 50% interquartile range and mode portrayed similar yield-factor relationship. In summary, fitting spatial yield-density models considering yield data distribution is critical to upscale site-specific models to larger spatial domains. [ABSTRACT FROM AUTHOR]

Tillage system and Pfertilizer placement can affect plant root growth and therefore water and nutrient uptake. The objective of this study was to evaluate the effect of P fertilizer placement and tillage system on soybean [Glycine max (L.)] root growth and grain yield under induced drought stress. A field study was performed at two locations in southern Brazil, during the 2014/2015 season. Phosphorus fertilizer placement and tillage combinations were evaluated using triple superphosphate at 31 kg P ha-1. Treatments included: (i) strip-tillage with deep band (ST-DB); (ii) strip-tillage with band-applied 5 by 5 cm (ST-B); (iii) no-till with broadcast (NT-BR); (iv) no-till with band-applied 5 by 5 cm (NT-B); and (v) no-till with surfaceband (NT-SB). Root length density (RLD) and root diameter were evaluated at 0- to 25-cm depth in 5-cm intervals. Yield was evaluated under rainfed as well as under induced drought conditions. The ST-DB treatment showed increased total RLD among treatments, with about 58% greater RLD than the NT-BR treatment, and 46% greater RLD than the NT-B treatment at the 15- to 25-cm soil depth. Furthermore, the soybean yield penalty with the ST-DB treatment was lower than any other treatment with a yield reduction of about 9 and 0.3% at respective locations under induced drought stress. Results from our study showed that the ST-DB treatment contributed to enhance soybean root growth at deeper soil layers and improved overall resilience to induced drought. [ABSTRACT FROM AUTHOR]

The use of mathematical models predicting SOC dynamics can provide relevant information about the C storage potential of agricultural soils. We evaluated three mathematical models (first-order kinetic, C saturation, and a proposed kinetic to saturation) predicting SOC dynamics and steady-state SOC of a Hapludoll from central kansas. The study was based on a long-term experiment (17 yr) assessing soil tillage systems (chisel tillage [CT] and no- till [NT]) and N fertilizer sources (168 kg N ha-1 as NH4NO3 [MF], cattle manure [OF], and a control treatment without N [Co]. The soil under NT (0-5 cm) had significant SOC accumulation (>0.23 Mg C ha-1 yr-1) regardless of fertilization source, while the CT soil had negligible changes in SOC (<0.12 Mg C ha-1 yr-1) without the addition of organic fertilizer as an external C source. organic fertilization increased the original SOC by 56 and 192%, reaching steady state at 15.9 and 28.0 Mg ha-1 in CT and NT soils, respectively. The SOC predicted by all three models had significant correlations (r > 0.80, p < 0.05) with measured SoC. However, the C saturation model overestimated the measured SOC under C-depleted conditions, failing RMSE and lack-of-fit tests, while the first-order kinetic model overestimated NT OF steady-state SOC by up to 58% in relation to the maximum SOC storage capacity determined for NT soils. The SOC predicted by the kinetic to saturation model agreed with both measured SOC and the maximum SOC storage capacity of NT soils. The kinetic to saturation model can be used for long-term simulation of SOC dynamics in soils that are either C depleted or close to saturation. [ABSTRACT FROM AUTHOR]

Increasing global demand for oil seeds and cereals during the past 50 years has caused an expansion in the cultivated areas and resulted in major soil management and crop production changes throughout Bolivia, Paraguay, Uruguay, Argentina and southern Brazil. Unprecedented adoption of no-tillage as well as improved soil fertility and plant genetics have increased yields, but the use of purchased inputs, monocropping i.e., continuous soybean (Glycine max (L.) Merr.), and marginal land cultivation have also increased. These changes have significantly altered the global food and feed supply role of these countries, but they have also resulted in various levels of soil degradation through wind and water erosion, soil compaction, soil organic matter (SOM) depletion, and nutrient losses. Sustainability is dependent upon local interactions between soil, climate, landscape characteristics, and production systems. This review examines the region's current soil and crop conditions and summarizes several research studies designed to reduce or prevent soil degradation. Although the region has both environmental and soil resources that can sustain current agricultural production levels, increasing population, greater urbanization, and more available income will continue to increase the pressure on South American croplands. A better understanding of regional soil differences and quantifying potential consequences of current production practices on various soil resources is needed to ensure that scientific, educational, and regulatory programs result in land management recommendations that support intensification of agriculture without additional soil degradation or other unintended environmental consequences. [ABSTRACT FROM AUTHOR]

Cover crops (CC), particularly legumes, are key to promote soil carbon (C) sequestration in no-tillage. Nevertheless, the mechanisms regulating this process need further elucidation within a broad comprehensive framework. Therefore, we investigated effects of CC quality: black oat (Avena strigosa Schreb) (oat), common vetch (Vicia sativa L.) (vetch), and oat + vetch on carbon dioxide-C (CO2-C) emission (124 days) under conventional- (CT), minimum- (MT) and no-tillage (NT) plots from a long-term experiment in Southern Brazil. Half-life time (t1/2) of CC residues and the apparent C balance (ACB) were obtained for CT and NT. We linked our data to long-term (22 years) soil C and nitrogen (N) stocks and crop yield data of our experimental field. Compared to CT, NT increased t1/2 of oat, oat + vetch and vetch by 3.9-, 3.1- and 3-fold, respectively; reduced CO2-C emissions in oat, oat + vetch and vetch by 500, 600 and 642 kg ha−1, respectively; and increased the ACB (influx) in oat + vetch (195%) and vetch (207%). For vetch, CO2-C emission in MT was 77% greater than NT. Legume CC should be preferentially combined with NT to reduce CO2-C emissions and avoid a flush of N into the soil. The legume based-NT system showed the greatest soil C and N sequestration rates, which were significantly and positively related to soybean (Glycine max (L.) Merrill) and maize (Zea mays L.) yield. Soil C (0–90 cm depth) and N (0–100 cm depth) sequestration increments of 1 kg ha−1 corresponded to soybean yield increments of 1.2 and 7.4 kg ha−1, respectively. [ABSTRACT FROM AUTHOR]