Effect of integrated nutrient management modules on water stable aggregates and carbon distribution in aggregate size in Vertisol of central India

Soil aggregate and organic carbon (OC) are deemed as potent indicators of soil structure and quality. An investigation was carried out with maize crop in kharif season during 2015-2016 under long-term interagted nutrient management module and examine its approach on soil organic carbon and aggregation. The soil aggregate formation was separated using a wet sieving method. The large macro-aggregates varied from 3-10 % under different treatments whereas, about 72-82% of aggregate corresponded to small macro-aggregates (0.25–2 mm) followed by micro-aggregates which constituted about 12-17%. Application of organics increased the proportion of small macro-aggregates. The highest content was recorded in T3, T4, T11 and T12. This is because soil organic matter has been recognized as binding agent of soil particles for the formation of water stable aggregates. It was observed that there was improvement in the percentage of water stable aggregates (>250 mm) due to integrated use of recommended dose of NPK and farmyard manure (FYM). However, the effect was not statistically significant. In general large macro-aggregates contained higher concentration of soil organic carbon than other size fractions. Highest concentration of C (0.79%) in large aggregate size class was recorded in treatment T11 where FYM was applied every season. Similarly, application of 5 t of FYM in T5 along with chemical fertilizer also recorded higher soil carbon concentration. The similar trend was recorded in T9 and T10 also where poultry manure and FYM was applied along with other organic sources of nutrients.