减氮配施生物炭对土壤肥力和水稻产量的补偿效应与机制

Compensation Effect and Mechanism of Nitrogen Reduction Combined with Biochar Application on Soil Fertility and Rice Yield

摘要:

氮素是水稻生长所必需的营养元素。为了提高产量往往过量施加氮肥，这不仅导致氮肥利用率低，还破坏了土壤质量，减少氮肥施用则会导致水稻减产。为探究土壤改良剂（生物炭）能否补偿减氮带来的负面影响，本研究采用盆栽试验，设置常规施氮（氮肥施用量110 kg/hm2，CK）、减氮10%（C1）及减氮10%条件下配施2.5%生物炭（C2）和5%生物炭（C3）4个处理，探讨在减少氮肥使用条件下生物炭对土壤肥力及水稻产量的补偿效应及机制。结果表明：减氮10%对土壤综合肥力无显著影响，施加生物炭可有效地提高土壤肥力，且添加5%生物炭对土壤肥力的提升效果优于添加2.5%生物炭。减氮10%导致水稻产量显著降低，而生物炭施加可一定程度补偿减氮造成的减产，其中添加2.5%生物炭对水稻产量的补偿效果优于添加5%生物炭，但仍未恢复到常规施氮水平。采用结构方程探究减氮和施加生物炭条件下水稻产量的驱动因素，结果表明，减氮配施生物炭通过改变土壤pH值、全钾含量、铵态氮含量和硝态氮含量，进而直接或间接影响水稻产量，其中铵态氮含量和硝态氮含量是主要的调控因子，其不仅直接影响水稻产量，还可通过调控每穗粒数、有效穗数和千粒质量间接影响水稻产量的形成；pH值和全钾含量对水稻产量有负面效应。本研究可为东北黑土区水稻种植业化肥减量和生物炭的高效利用提供科学依据。

Abstract:

Nitrogen is an essential nutrient for the growth of rice. In order to increase yield, excessive application of nitrogen fertilizer often leads to low nitrogen utilization efficiency and also damages soil quality. Reducing the application of nitrogen fertilizer will lead to a decrease in rice yield. It is worth exploring whether biochar, as a soil amendment, can compensate for the negative effects of nitrogen reduction. A pot experiment was conducted to investigate the compensatory effects and mechanisms of biochar on soil fertility and rice yield under four conditions: conventional nitrogen application (nitrogen fertilizer application rate of 110 kg/hm2, CK), 10% nitrogen reduction (C1), and 2.5% (C2) and 5% (C3) concentration biochar application under 10% nitrogen reduction. The results showed that the nitrogen fertilizer reduced by 10% had no significant effect on soil comprehensive fertility. Applying biochar could effectively improve soil fertility, and 5% concentration of biochar had better effect on soil fertility than that of 2.5% concentration. Reducing nitrogen by 10% significantly reduced rice yield, and the application of biochar can compensate for the reduction caused by nitrogen reduction to some extent. Among them, the compensation effect of 2.5% concentration of biochar on rice yield was better than that of 5% concentration, but it had not yet returned to the conventional nitrogen application level. Exploring the driving factors of rice yield under nitrogen reduction and biochar application conditions by using structural equations, the results showed that reducing nitrogen fertilizer combined with biochar can directly or indirectly affect rice yield by changing soil pH value, total potassium, ammonium nitrogen, and nitrate nitrogen content. Among them, ammonium nitrogen and nitrate nitrogen content were the main regulatory factors, which not only directly affected rice yield, but also indirectly affected the formation of rice yield by regulating the number of grains per panicle, effective panicle, and thousand grain weight; pH value and total potassium content had negative effects on rice yield. The research result can provide scientific basis for the reduction of fertilizer and efficient utilization of biochar in rice cultivation in the black soil area of Northeast China.