Effects of the Autumn Incorporation of Rice Straw and Application of Lime Nitrogen on Methane and Nitrous Oxide Emissions and Rice Growth of a High-Yielding Paddy Field in a Cool-Temperate Region in Japan

Fumiaki Takakai,Mimori Goto,Yoshihiro Kaneta,Haruki Watanabe,Keiko Hatakeyama,Takashi Sato,Kentaro Yasuda

doi:10.3390/agriculture11121298

Abstract

The effects of autumn plowing and lime nitrogen application on rice straw decomposition, CH4 and N2O emission and rice growth in the following year in a high-yielding rice cultivated paddy field were evaluated for two years. The experimental plots were set up, combining different times of rice straw (750 g m−2) incorporation into the soil by plowing (autumn or the following spring), with and without lime nitrogen application in autumn (5 g-N m−2). Autumn plowing promoted the decomposition of rice straw, but the application of lime nitrogen did not show a consistent trend. The soil pH was high (7.3) at the studied site, and the alkaline effect of lime nitrogen may not have been significant. As with straw decomposition, CH4 emissions were suppressed by autumn plowing, and no effect from the lime nitrogen application was observed. It was also suggested that the straw decomposition period may be shorter and the CH4 emissions may be higher in high-yielding cultivars that require a longer ripening period than in normal cultivars. The effect of both treatments on N2O emission was not clear. Both the autumn plowing of rice straw and lime nitrogen application were effective in promoting rice growth and increasing rice yield.

Highlights

IntroductionThe demand for rice, a staple food in Japan, has been decreasing by80,000 tons annually [1]
In Japan, rice cultivation has been mechanized since the 1960s, and shredded rice straw is spread on the field when paddy rice is harvested by combine harvesters
The carbon decomposition rates in the spring plowing plots were increased by lime nitrogen application in 2017, but decreased by lime nitrogen application in 2018

Summary

Introduction

The demand for rice, a staple food in Japan, has been decreasing by80,000 tons annually [1]. The cultivation area of rice for new sources of demand, such as rice flour, feed, etc., increased by about 120,000 ha from 2008 to 2018. This is because methods promoting the effective utilization of paddy fields through the cultivation of rice for new sources of demand have been recommended in order to improve. Since low-cost paddy rice cultivation is important for meeting the new demands of rice cultivation, high-yielding varieties are mainly being adopted. In Japan, rice cultivation has been mechanized since the 1960s, and shredded rice straw is spread on the field when paddy rice is harvested by combine harvesters. The problem caused by undecomposed rice straw is likely to be more serious when high-yielding varieties are grown [2]

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