Influence of redox conditions and rice straw incorporation on nitrogen availability in fertilized paddy soils

Abstract

Temporal nitrogen (N) availability in fertilized rice paddies is the result of a balance of processes, mainly the gross rates of N mineralization, microbial and abiotic immobilization and N losses. Water and crop residue management practices often confound these established relationships making N the most difficult nutrient to manage in rice cropping systems. To investigate and quantify the interactive effects of soil redox conditions and straw incorporation on temporal fertilizer-N availability we treated a paddy soil with enriched ammonium-15 N and incubated for 160 days under flooded or non-flooded conditions, with or without the addition of rice straw. Changes in total available N as well as available and immobilized fertilizer-derived N (FDN) during incubation were evaluated. Under both oxic and waterlogged soils about 45-53% of applied N was rapidly immobilized. Whereas in the former most of this FDN was released contributing to the available N pool, flooded soils experienced significant losses from the soil/water system (≈ 67% of applied N). Addition of rice straw enhanced N immobilization, particularly under flooded conditions, that also contributed to limiting losses. Moreover, turnover of this labile organic matter pool supplied significant amounts of available N towards the later stages of the incubation, partly compensating for the immobilization of fertilizer-N.

Effects of straw incorporation on nitrogen absorption of split fertilizer applications and on rice growth

“…The negative effects of straw incorporation in the early stage have been explained by N starvation (Fig. 3), toxic substances and intensely reducing conditions caused by straw decomposition (Tanaka and Nishida, 1996;Cucu et al, 2014). The variety of effects of straw incorporation at maturity are probably due to the differences in soil N availability; N fertilizer level and application method; the amount and method of straw incorporated; or the length of the growing season.…”

“…There are three possible reasons for this. (1) In the early stage of growth, intensely reducing conditions as a result of straw decomposition likely restricted the growth of subsurface roots; however, in the late stage (as the straw decomposition rate was falling), there were no longer significant differences in the redox conditions between the two straw treatments (Gao et al, 2004;Cucu et al, 2014). Olk et al (2007) reported that the decomposition of crop residues in a field trial was largely completed after 6 weeks of incorporation.…”

“…Olk et al (2007) reported that the decomposition of crop residues in a field trial was largely completed after 6 weeks of incorporation. (2) The decomposition of crop straw with a large C: N ratio often results in a net N immobilization phase followed by a net re-mineralization phase (Kanamori and Yasuda, 1979;Azam et al, 1991;Cucu et al, 2014).…”

“…However, researchers (Broadbent and Nakashima, 1965;Broadbent, 1966;Cucu et al, 2014) have reported that (once being immobilized by decomposition of straw with a high C: N ratio), fertilizer 15 N will be difficult to remineralize, so that late-stage net re-mineralization cannot offset the early-stage net immobilization even after months or seasons. Consequently, lower FNR p and a higher residual rate are inevitable when straw is incorporated (Masayna et al, 1985;Huang and Broadbent, 1989).…”

Reduction in Trace Element Mediated Oxidative Stress towards Cropped Plants via Beneficial Microbes in Irrigated Cropping Systems: A Review

“…Plant stressors impact yields of both summer and winter crops, including canola, wheat, sugar cane, corn, cotton, and rice. The main abiotic plant stressors that impact crop growth include fluctuating temperatures, soil pH, salinity, soil water availability (drought), diurnal cycling changes, and availability of soil nutrients [1][2][3][4][5][6][7][8][9][10][11][12]. Summer crops grown in Australia, including rice, cotton, and sugar cane, require high volumes of water, which is applied using irrigation systems.…”