Partial substitution of chemical fertilizer with organic fertilizer is emerging as a promising measure to achieve sustainable agriculture with high crop yields and low environmental risks. How much synthetic nitrogen fertilizer can be replaced by each unit of organic fertilizer? How to balance the economic benefits against the environmental risks? There is still a lack of long-term field observations to address these challenges. An 8-year field fertilization experiment (initiated in 2014) was conducted using a split-plot design with five nitrogen rates (N: N0, N75, N150, N225, N300) as main plots in combination with two manure rates (M: M0 and M1) as subplots. The results indicated that the grain yield and economic benefits slowly increased or even decreased after the N rate exceeded 150 kg ha. The N rate required for M1 to reach the highest yield of M0 was 105 kg ha, which was 123 kg ha less than the 228 kg ha required for that of the M0. At this point, each ton of manure can replace 4.1 kg of synthetic N. Manure application considerably increased the net economic benefit by 10.2 %. The nitrate residue in the 0−200-cm soil layer sharply increased with the N rate, particularly when the N rate exceeded 150 kg ha. An N rate exceeding 150 kg ha was more likely to cause nitrate leaching to the deeper soil layer (below 200 cm) during the summer fallow season. NO emissions and NH volatilization gradually increased with the nitrogen and manure rates, and both exhibited nonlinear distribution curves with the N rate. Pursuing higher grain yields reduced economic benefits and caused more N pollution. The Structural equation modeling (SEM) results showed that manure application significantly increased the water storage rate during the summer fallow period by 4.1 %, which would promote wheat N uptake and ultimately reduce reactive nitrogen losses and improve economic benefits. Taken together, M1N150 was the optimal fertilization scheme to synergistically achieve high yield, high economic benefits and low environmental risks in Guanzhong Plain of China.

中文翻译：

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优化化学氮肥与粪肥搭配可提高旱地小麦产量和经济效益，同时降低环境风险


用有机肥部分替代化肥正在成为实现农作物高产、环境风险低的可持续农业的一项有前途的措施。每单位有机肥可替代多少合成氮肥？如何平衡经济效益与环境风险？仍然缺乏长期的实地观察来应对这些挑战。 2014年开始，采用裂区设计，以5种施氮量（N：N0、N75、N150、N225、N300）为主小区，结合2种施肥量（M：M0），进行了为期8年的大田施肥试验。和 M1) 作为子图。结果表明，施氮量超过150 kg·ha后，粮食产量和经济效益缓慢上升甚至下降。 M1达到M0最高产量所需的施氮量为105 kg ha，比M0所需的228 kg ha少了123 kg ha。此时，每吨粪肥可替代合成氮4.1公斤，施用粪肥可大幅增加净经济效益10.2%。 0~200 cm土层中硝酸盐残留量随着施氮量的增加而急剧增加，特别是当施氮量超过150 kg·ha时。夏季休耕期间，施氮量超过 150 kg/ha 更容易导致硝酸盐淋失至深层土层（200 cm 以下）。 NO排放量和NH挥发量随着施氮量和施肥量的增加而逐渐增加，且均随施氮量呈现非线性分布曲线。对粮食高产的追求降低了经济效益，并造成了更多的氮污染。结构方程模型（SEM）结果表明，施用粪肥使夏季休耕期间的蓄水率显着提高了4倍。1%，促进小麦氮素吸收，最终减少活性氮损失，提高经济效益。综上所述，M1N150是关中平原协同实现高产、高经济效益、低环境风险的最佳施肥方案。