Long-term impact of legume-inclusive diversification and nutrient management practices on phosphorus dynamics in alkaline Fluvisol.

An insight into the dynamics of soil phosphorus (P) pools with long-term cropping/management practices would help in designing efficient and sustainable management module(s). The study aimed to investigate the long-term impact of diversified rice-based rotations and variable nutrient management practices on the dynamic composition of P pools and their influence on systems' base-crop productivity in an alkaline soil of Indo-Gangetic plain (Fluvisol). Treatments consisted of four rotations [rice-wheat (R-W), rice-wheat-mungbean (R-W-Mb), rice-wheat-rice-chickpea (R-W-R-C), rice-chickpea (R-C)] each with three nutrient treatments [control (CT), integrated nutrient management (INM), sole-chemical fertilizers (CF)]. Notably, R-C exhibited higher levels of bioavailable-P (soluble-P, Ca2-P, labile-Po), particularly in subsurface soil depth (0.2-0.4 m) compared to other rotations. Likewise, the inclusion of chickpea every alternate year (R-W-R-C) resulted in higher Ca2-P (40%), labile-Pi (15%), labile-Po (11%), and moderately labile Po (8%) compared to R-W rotation demonstrating an increased significance of chickpea in maintaining a favorable soil P regime in alkaline soil. Both R-C and R-W-R-C reduced the surface-to-subsurface depth ratio (SSBR) of soluble-P and Ca2-P while increasing the ratio for microbial biomass P. Even with a suboptimal fertilizer-P rate, INM significantly increased soluble-P (4-33%), labile-Po (13-17%), microbial biomass P (10-26%), moderately labile-Po (4-17%) compared to CF and exhibited higher SSBR values. Correlation analysis demonstrated the substantial influence of very-labile carbon, microbial and phosphatase activities on P availability. The treatment-induced changes in labile-P pools significantly influenced rice (base-crop) yields. In conclusion, chickpea-inclusive diversification and INM could be a sustainable approach to enhance P bioavailability and crop productivity in tropical rice soils.

Long-term impact of pulses and organic amendments inclusion in cropping system on soil physical and chemical properties.

Mono-cropping of maize-wheat, mechanical disintegration of soils, and continuous chemical fertilization have deteriorated soil health in the Indo-Gangetic Plains. We studied the long-term impact of pulse-based cropping systems with integrated nutrient management on soil physical and chemical properties and yield sustainability. We evaluated four different cropping systems: (1) maize-wheat (M-W), (2) maize-wheat-mungbean (M-W-Mb), (3) maize-wheat-maize-chickpea (M-W-M-C), (4) pigeonpea-wheat (P-W) each with three degrees of soil fertilization techniques: (1) unfertilized control (CT), (2) inorganic fertilization (RDF), and (3) integrated nutrient management (INM). The field experiment was undertaken in a split-plot design with three replications each year with a fixed layout. P-W and M-W-Mb systems enhanced soil properties such as volume expansion by 9-25% and porosity by 7-9% (p < 0.05) more than M-W, respectively. P-W and M-W-Mb increased soil organic carbon by 25-42% and 12-50% over M-W (RDF). P-W system enhanced water holding capacity and gravimetric moisture content by 10 and 11% (p < 0.05) than M-W. Pulse-based systems (P-W and M-W-Mb) had higher available nitrogen (8-11%), phosphorus (42-73%), and potassium (8-12%) over M-W (p < 0.05). M-W-Mb increased 26% maize yield and 21% wheat yield over M-W (p < 0.05) at the thirteenth crop cycle. P-W system had a higher sustainable yield index (p < 0.05) of wheat over the M-W. Thus, pulse inclusion in the cropping system in combination with INM can enhance physical and chemical properties vis-à-vis sustainable yield index over the cereal-cereal system.

Conventional and Zero Tillage with Residue Management in Rice-Wheat System in the Indo-Gangetic Plains: Impact on Thermal Sensitivity of Soil Organic Carbon Respiration and Enzyme Activity.

The impact of global warming on soil carbon (C) mineralization from bulk and aggregated soil in conservation agriculture (CA) is noteworthy to predict the future of C cycle. Therefore, sensitivity of soil C mineralization to temperature was studied from 18 years of a CA experiment under rice-wheat cropping system in the Indo-Gangetic Plains (IGP). The experiment comprised of three tillage systems: zero tillage (ZT), conventional tillage (CT), and strip tillage (ST), each with three levels of residue management: residue removal (NR), residue burning (RB), and residue retention (R). Cumulative carbon mineralization (Ct) in the 0-5 cm soil depth was significantly higher in CT with added residues (CT-R) and ZT with added residues (ZT-R) compared with the CT without residues (CT-NR). It resulted in higher CO2 evolution in CT-R and ZT-R. The plots, having crop residue in both CT and ZT system, had higher (p < 0.05) Van't-Hoff factor (Q10) and activation energy (Ea) than the residue burning. Notably, micro-aggregates had significantly higher Ea than bulk soil (~14%) and macro-aggregates (~40%). Aggregate-associated C content was higher in ZT compared with CT (p < 0.05). Conventional tillage with residue burning had a reduced glomalin content and ß-D-glucosidase activity than that of ZT-R. The ZT-R improved the aggregate-associated C that could sustain the soil biological diversity in the long-run possibly due to higher physical, chemical, and matrix-mediated protection of SOC. Thus, it is advisable to maintain the crop residues on the soil surface in ZT condition (~CA) to cut back on valuable C from soils under IGP and similar agro-ecologies.