Effect of organic amendments at optimum irrigation level on maize yield, soil carbon dynamics and soil physical health

Abstract

Aridity, brackish water, low organic matter, poor soil structure and intensive cropping are main challenges of Pakistan’s agriculture. Sustained soil quality and productivity are needed to feed the growing population that can only be achieved through sustainable management practices. A stepwise mechanistic study was conducted for restoration of soil carbon and re-establishment of degraded soil with sustained crop productivity. A preliminary study was conducted mixing different organic substrates (farm manure, poultry manure, biochar, flyash, wheat straw, sugarcane bagasse, rice husk and molasses) @ 1.5% of soil weight and incubated for 42 days. Farm manure, poultry manure and molasses yielded more particle aggregation, biological activity and macroaggregate carbon on each sample collection and were selected through trending of parameters in cluster analysis. These selected treatments were then applied in pot study while maintaining soil water contents @ 50, 75, 100 and 125% of available water contents (AWC), using maize as test crop. Different maize root parameters i.e. length (44.55 cm), fresh and dry weights (71.10 g and 24.30 g), diameter (1.73 mm), volume (0.24 cm3) and length density (7.4 × 10-3 cm cm-3) were calculated in pots receiving farm manure as organic amendment and soil water content maintained at 75% AWC. All parameter values were statistically at par with all other organic treatments at 75% AWC and 100% AWC but significantly higher than all plant parameters of each organic treatment at 50% or 125% AWCs. Using cluster analysis 75% AWC level was selected as best level for plant growth and that was maintained in the field trials. During two year field experimentation physical indices of soil i.e. water stable soil aggregates (40.7 and 39.9%), soil organic carbon (12.6 and 12.1 g kg-1), saturated hydraulic conduction (27.9 and 27 mm h-1), rate of infiltration (26.1 and 25.4 mm h-1), soil total porosity/void ratio (0.49 and 0.48 m3 m-3) were observed where farm manure was added in soil as treatment. Agronomic characteristics of maize i.e. corn yield (9.47 and 9.21 Mg ha-1) and use efficiency of irrigation water (11.1 and 10.8 kg mm-1 yr-1) were found in farm manure treated plots. All of these values were vigilantly greater than control but were found statistically similar to other treatments. Organic addition recovered soil structure that resulted in water retention, good aeration and root penetration which helped to achieve yield goals along with saving by 25% irrigation water. The farmers are primarily recommended to use organic manures along with mineral fertilizers and synthetically active biological products to sustain production, saving soils and water for our next generation.