Changes in the Nitrogen Budget and Soil Nitrogen in a Field with Paddy–Upland Rotation with Different Histories of Manure Application

Fumiaki Takakai,Kazuhiro Kon,Yoshihiro Kaneta,Takemi Kikuchi,Tomomi Sato,Takashi Sato,Kensuke Sato,Masato Takeda,Shinpei Nakagawa

doi:10.3390/agriculture7050039

Abstract

In northern Japan, declines in soil nitrogen fertility have occurred in paddy–upland rotation systems with soybean cultivation. A six-year lysimeter experiment was conducted to evaluate the nitrogen budget in paddy–upland rotation (three-year for upland soybean, then three-year for flooded paddy rice) and to clarify the effect of preceding compost application (immature or mature compost over four consecutive years of forage rice cultivation) on the nitrogen budget and soil nitrogen fertility. Available soil nitrogen throughout the experimental period and soybean and rice yields in both compost application plots tended to be higher than those in the control plot. The nitrogen budgets during both soybean and rice cultivation were negative, and the amount of nitrogen loss in both compost application plots tended to be higher than that in the control plot. The nitrogen loss during rice cultivation (−2.3 to −4.3 g N m−2 year−1) was less than that during soybean cultivation (−9.6 to −14.6 g N m−2 year−1). Nitrogen loss estimated based on the nitrogen budget agreed well with that estimated based on changes in soil nitrogen storage during soybean cultivation but not during rice cultivation, suggesting underestimation of nitrogen loss from the rice paddy.

Highlights

In Japan, rice production has been adjusted over 40 years due to decrease in domestic consumption.The area of paddy fields in Japan has continued to decline at a rate of about 20,000 ha−1 year−1, and the total area was 2,355,000 ha in 2010
Loss of soil organic matter in paddy fields are considered to be lower than those in upland fields owing to slow decomposition under flooded and anaerobic condition [34,35]
During the soybean cultivation period, obvious decrease in soil nitrogen storage occurred at 0–10 cm in both compost application plots where their nitrogen storage increased owing to preceding compost application

Summary

Introduction

In Japan, rice production has been adjusted over 40 years due to decrease in domestic consumption. The area of paddy fields in Japan has continued to decline at a rate of about 20,000 ha−1 year−1 , and the total area was 2,355,000 ha in 2010. The paddy–upland rotation system, which alternates every few years between paddy rice cultivation and upland crop cultivation in drained paddy fields, has become a popular practice. Soybean is the main crop cultivated in the converted upland fields in Japan. Depletion of available soil nitrogen and a subsequent decline in soybean yield in upland fields in the repeated paddy–upland rotation system have been reported in northern Japan [2]

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