Carbon and Nitrogen Mineralization in Dark Grey Calcareous Floodplain Soil Is Influenced by Tillage Practices and Residue Retention.

Nazmus Salahin,Walaa F Alsanie,Sharif Ahmed,Mohammad Jahiruddin,Akbar Hossain,Ahmed Gaber,Md Khairul Alam,Richard W Bell

doi:10.3390/plants10081650

Abstract

Very little is known about the changes that occur in soil organic carbon (SOC) and total nitrogen (TN) under an intensive rice-based cropping system following the change to minimal tillage and increased crop residue retention in the Gangetic Plains of South Asia. The field experiment was conducted for 3 years at Rajbari, Bangladesh to examine the impact of tillage practices and crop residue retention on carbon (C) and nitrogen (N) cycling. The experiment comprised four tillage practices—conventional tillage (CT), zero tillage (ZT), strip-tillage (ST), and bed planting (BP) in combination with two residue retention levels—increased residue (R50%) and low residue (R20%—the current practice). The TN, SOC, and mineral N (NH4+-N and NO3−-N) were measured in the soil at different crop growth stages. After 3 years, ZT, ST, and BP sequestered 12, 11, and 6% more SOC, and 18, 13, and 10% more TN, respectively than the conventional crop establishment practice at 0–5 cm soil depth. The accumulation of SOC and TN was also higher compared to the initial SOC and TN in soil. Among the tillage practices, the maximum SOC and TN sequestration were recorded with ST and with R50% that might be attributed to reduced mineralization of C and N in soil particularly with increased residue retention, since decay rates of potentially mineralizable C was lower in the ST with both the residue retention practices. Increased residue retention and minimum tillage practices after nine consecutive crops has altered the C and N cycling by slowing the in-season turnover of C and N, reducing the level of nitrate-N available to plants in the growing season and increasing retained soil levels of SOC and TN.

Highlights

Changing management practices, climate variables, and input use may alter the soil biogeochemical processes [1,2,3,4]
In the following two cropping years, the highest system residue retention was recorded from the ST and bed planting (BP) practices with 50% residue retention (Table 1)
zero tillage (ZT), zero-tillage; ST, strip-tillage; BP, bed planting; CT, conventional tillage; R20%, 20% residue retention; R50%, 50% residue retention; LSD, least significant difference; NS, not significant; CV, coefficient of variation; * = p < 0.05, ** = p < 0.01

Summary

Introduction

Climate variables, and input use may alter the soil biogeochemical processes [1,2,3,4]. The major terrestrial pool of C, N, and other nutrients comes from soil organic matter (SOM) while these elements are dynamically cycled through continuous changes by microbial immobilization and mineralization [8]. The biogeochemical cycles of C and N in the paddy-growing ecosystem are very active due to alternate wetting and drying of soils, resource consumptive agricultural practices, injudicious agricultural input use while striving for higher yield goals, high cropping intensity, etc. Prediction of soil C and N mineralization when crop residues are retained and build up soil organic matter in wetland soils may improve the profitability and sustainability of agriculture by allowing farmers to decrease the input of N fertilizer that optimizes crop yield. Inefficient use of N fertilizer may cause undesirable environmental impacts, mainly through gaseous N losses by denitrification and/or ammonia volatilization [10]

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