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Excessive application of farmyard manure reduces rice yield and enhances environmental pollution risk in paddy fields

Abe, Susumu S., Hashimoto, Seiko, Umezane, Takayuki, Yamaguchi, Takeshi, Yamamoto, Sadahiro, Yamada, Satoshi, Endo, Tsuneyoshi, Nakata, Noboru
Archiv für Acker- und Pflanzenbau und Bodenkunde 2016 v.62 no.9 pp. 1208-1221
animal manures, chemical oxygen demand, field experimentation, grain yield, mineral fertilizers, nitrogen, paddies, phosphorus, potassium, rice, risk, soil fertility, soil nutrients, soil pollution, surface water, water quality, yield components, Japan
The present study examined the effect of excessive application of farmyard manure (FM) on rice production and environmental pollution in paddy fields of Japan. A long-term field experiment was conducted during the period 1976–2006 to examine the trends of rice yield and yield components as affected by the excessive FM application (20 Mg ha ⁻¹ year ⁻¹ containing 110 kg N, 180 kg P ₂O ₅, and 320 kg K ₂O). Rice growth, soil fertility, and surface water quality were also assessed in the final year (2006). The results obtained were compared with those of a conventional practice with recommended doses of inorganic fertilizer (IF), i.e. 85 kg N, 68 kg P ₂O ₅, and 53 kg K ₂O ha ⁻¹ year ⁻¹, and an unfertilized control (CR). The excessive FM application resulted in a gradual decrease in grain yield, which was mostly explained by the reduction of grain fertility under the luxuriant rice growth. This reduction may have been due to the higher accumulation of soil nutrients such as N, P, and K. Moreover, the excessive FM application increased chemical oxygen demand, total P, and soluble K concentrations in the paddy surface water and their effluent loads compared to the conventional practice with the recommended IF application.