Precision Agriculture Practices Improves Soil Aggregation, Aggregate Associated Organic Carbon Fractions and Nutrient Dynamics in Cereal-based Systems of North-West India: An Overview
Authors: Gupta S. K. , Naresh R. K. , Chandra M. Sharath , Mrunalini Kancheti 
Published: May 2020

Precision farming uses proximal and remote sensor surveys to delineate and track in-field variations in soil and crop attributes, directing variable input rate control, such that in-season management can be sensitive, e.g. matching strategic application of nitrogen fertilizer to site-specific conditions. It has the ability to increase productivity in the processing and use of nutrients, ensuring that nutrients do not leach out or accumulate in excessive amounts in areas of the field, causing environmental problems. Tillage systems can change the dynamics of organic carbon in soil and microbial biomass in soil by adjusting aggregate shape and distribution of C within aggregates. The effects of tillage on soil organic carbon (SOC) and soil aggregate nutrient content can differ spatially and temporarily, and for different types of soil and cropping systems. The maximum (19.2 percent) and minimum (8.9 percent) proportion of total aggregated carbon was retained in surface soil, with fractions of 2 mm and 0.1-0.05 mm size respectively. At a depth of 0-7 cm soil MBC under plowing tillage was slightly higher than rotary tillage, but EOC was just opposite. Rotary tillage had much higher soil TOC than plowing tillage at a depth of 7-14 cm. Nevertheless, under plowing tillage, TOC, DOC, and MBC were significantly higher than rotary tillage except for EOC, at 14-21 cm depth. A significant proportion of the total SOC was found to be captured under both surface (67.1 percent) and sub-surface layers (66.7 percent) by the macro-aggregates (2-0.25 mm), leaving rest in micro-aggregates and particles shaped as "silt + clay."

Fine POC, LFOC and microbial biomass can be useful early signs of alterations in organic topsoil C. Conversely, LFOC and DOC are important subsoil indicators. Under two tillage regimes, surface soil (0-15 cm) was fractionated into aggregate sizes (4.76 mm, 4.76-2.00 mm, 2.00-1.00 mm, 1.00-0.25 mm, 0.25-0.053 mm, 0.053 mm). Tillage substantially decreased the proportion of macro-aggregate fractions (2.00 mm) and thus improved aggregate stability by 35 per cent relative to RNT, indicating that tillage practices for this subtropical soil resulted in structural changes in soil. The highest SOC was in the fraction of 1.00-0.25 mm (35.7 and 30.4 mg / kg respectively for RNT and CT), while the lowest SOC was in fractions of micro-aggregate (0.025 mm) and silt + clay (0.053 mm) (19.5 and 15.7 mg / kg respectively for RNT and CT). Application of inorganic fertilizer may maintain soil organic carbon (SOC) concentrations, whereas long-term application of manure alone or in combination with NPK (M and NPK + M) may significantly increase SOC content compared to unfertilized land. Application of manure substantially increased the proportion of large macro-aggregates (2000 μm) relative to the regulation, thus resulting in a corresponding decrease in the percentage of micro-aggregates (53-250 μm). The labile element of organic carbon has been suggested as a delicate predictor of soil organic matter changes. Improving the soil organic carbon pool also increases resilience and eco-efficiency of the agro ecosystems.