The effect of stubble management and N-fertilization practices on the nitrogen economy under intensive rice cropping

Abstract

The fate of 15N-labelled fertilizer applied to rice (Oryza sativa L) was studied in microplots established within two field experiments comprising a range of stubble levels, stubble management techniques, N application rates and times. The first experiment investigated uptake of soil and fertilizer N in plots where application of 0 or 100 kg N ha-1 to the previous rice crop had produced 11.5 and 16.1 t ha-1 of stubble respectively. The stubble was then treated in one of four ways-burn (no till); burn then cultivated; incorporated in autumn or incorporated at sawing. Microplots within these large plots received 60 kg ha-1 of 5% 15N enriched urea at sowing, just prior to permanent flood (PF), or just after panicle initiation (PI) of the second crop. The second experiment was undertaken within a field in which half of the plots had stubble from the previous three rice crops burned, while the other plots had all stubble incorporated. In the fourth successive rice crop, the two stubble management systems were factorially combined with three N rates (0, 70 or 140 kg N ha-1) and three application times (PF, PI or a 50 : 50 split between PF and PI). Nitrogen uptake and retention in the soil were studied within 15N-labelled microplots established within each of these large plots. Only 4% of the 15N applied at sowing in the first experiment was recovered in the rice crop, while delaying N application to PF or PI increased this to an average of 20% and 44% respectively over the two experiments. The doubling of N application rate doubled fertilizer N uptake and also increased uptake of soil N at maturity by 12 kgN ha-1. Three years of stubble incorporation increased average uptake of fertilizer and soil N in the second experiment by 5 and 12 kg N ha-1 respectively. In both experiments, the soil was the major source of N, contributing 66-96% of total N uptake. On average, in the fourth crop, 20% of fertilizer N was in the grain, 12% in the straw and 3% in the roots, while 23% was located in the top 300 mm of soil. A further 3% was in the soil below 300 mm. The remaining 39% was lost, presumably by denitrification.

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

“…The increased rate of residue retained in the soil under minimal soil disturbance practice led to higher SOM content over the three years and a lower decay rate of PMC. Accordingly, increased residue retention gave the highest PMC after running into the zero-order and first rate exponential pool [ 32 , 64 ]. Alam et al [ 1 ] reported that the SP soils recorded higher Co values (relative to CT practice) under all crops in rice-upland triple cropping systems after 5 years, probably because of the higher C contents, and lower PMC decay rate.…”

“…Increased rate of high residue retained in the soil had higher TN content and a lower decay rate of PMN than low residue retention. Accordingly, increased residue retention gave the numerically highest PMN according to the model (zero-order and first rate exponential pool) used [ 32 , 64 ].…”

Evolution of Soil Extractable Nitrogen as Affected by Winter Flooding and Straw Burning in Southern Spain Rice Systems

“…In addition, bulk density increases, water content decreases, despite the soil is waterlogged, and gases are trapped in the mud layer. Some other studies [6,7] demonstrated that incorporating harvest remains during the fall or early winter led to lower nitrogen (N) immobilization and higher N availability in the soil, which resulted in a grain yield increase compared to the late straw incorporation [8].…”