土壤肥力对红壤性水稻土水稻产量和氮肥利用效率的影响

【目的】土壤肥力是红壤性稻田水稻丰产的基础。明确不同肥力对红壤性水稻土作物产量和氮肥利用效率的影响,为红壤性稻田土壤培肥和合理施肥提供科学依据。【方法】选取质地相似的不同肥力水平的红壤性水稻土进行盆栽试验(以土壤有机质的高低代表土壤肥力的高低),利用~(15)N同位素示踪技术研究不同肥力水平(F_L、F_M和F_H分别代表低肥力、中肥力和高肥力,其低、中、高肥力土壤的有机质含量分别为19.9、29.6、38.9 g·kg~(-1))和氮肥水平(N_0、N_(150)和N_(225)分别代表施氮量为0、150和225 kg·hm~(-2),共9个试验处理,分别为F_LN_0、F_LN_(150)、F_LN_(225)、F_MN_0、F_MN_(150)、F_MN_(225)、F_HN_0、F_HN_(150)和F_HN_(225))对水稻产量及其构成、氮肥吸收及其去向的影响。【结果】提升土壤肥力和施氮均能显著提高水稻的有效穗数、产量和总吸氮量。与N_0相比,F_L、F_M和F_H在N_(150)处理下的增产率分别为63%、40%、17%,而在N_(225)处理下的增产率分别为89%、55%和23%。在中、低肥力土壤上,增施氮肥能显著提高水稻产量,而F_HN_(150)和F_HN_(225)处理之间产量无显著差异。~(15)N示踪结果表明,相同施氮量条件下,水稻植株对肥料氮素和土壤氮素的吸收量均随土壤肥力的提高而增加。但是,水稻植株总吸氮量中来自土壤氮素的比例随土壤肥力的提高而增加,而来自肥料氮素的比例则随之降低。增施氮肥会增加水稻吸收肥料氮素的比例,降低其吸收土壤氮素的比例。F_L、F_M和F_H土壤水稻的平均氮肥回收率分别为42%、48%和52%,平均氮肥残留率分别为20%、23%和28%,平均氮肥损失率分别为38%、29%和20%。F_LN_(225)氮肥回收率显著高于F_LN_(150),F_M两个施氮量氮肥回收率无显著差异,而F_HN_(225)的氮肥回收率显著低于F_HN_(150)。提升土壤肥力能显著提高土壤微生物量氮、铵态氮和固定态铵的含量。【结论】提升土壤肥力能显著提高红壤性水稻土的水稻产量以及化肥氮的回收率和残留率,而降低氮肥损失率。在低肥力土壤上适当增加施氮量有利于增加产量和氮肥回收率;而在高肥力土壤上适当降低施氮量在保证较高水稻产量的同时,能够提高氮肥回收率、降低氮肥损失。

Effects of Soil Fertility on Rice Yield and Nitrogen Use Efficiency in a Red Paddy Soil

【Objective】 Soil fertility is the basis for high rice yield in the red paddy soil. It is critical to clarify the effects of different fertility levels on crop yield and nitrogen (N) use efficiency, thereby providing scientific evidence for soil fertility improvement and appropriate fertilizer management in red paddy soil. 【Method】 A pot experiment was carried out on red paddy soils with similar texture and different fertility levels (The level of soil organic matter represented the level of soil fertility) with the ¹⁵N isotopic tracer technique. The effects of soil fertility (F_L, F_M, and F_H represent low, medium, and high fertility soils with a soil organic matter 19.9, 29.6, 38.9 g·kg^-1, respectively) and N fertilizer rate (N₀, N₁₅₀, and N₂₂₅ represent the N application rate at 0, 150, and 225 kg·hm^-2, respectively), with 9 treatments (F_LN₀, F_LN₁₅₀, F_LN₂₂₅, F_MN₀, F_MN₁₅₀, F_MN₂₂₅, F_HN₀, F_HN₁₅₀, and F_HN₂₂₅) on rice yield and its composition, N uptake and its fate were investigated. 【Result】 Increasing soil fertility and N fertilization significantly increased the number of effective panicles, yield, and total N uptake of rice. Compared with N₀, F_L, F_M, and F_H increased rice yield by 63%, 40% and 17% under N₁₅₀ treatment, respectively, with 89%, 55% and 23% under N₂₂₅ treatment, respectively. In medium and low fertility soils, increasing the N rate significantly increased rice yield, whereas no significant difference was found between the F_HN₁₅₀ and F_HN₂₂₅ treatments. Using the ¹⁵N tracing technique, we found that the uptake of fertilizer N and soil N by rice plants increased with the increasing soil fertility under the same N application rate. However, the proportion of N derived from soil (Ndfs) increased with the increasing soil fertility, while the proportion of N derived from fertilizer (Ndff) showed the opposite trend. Increasing N fertilization rate led to an increase in Ndff, while reducing Ndfs. The average N recovery efficiency (NRE) of F_L, F_M, and F_H was 42%, 48% and 52%, respectively; with the average N fertilizer residue rate of 20%, 23% and 28%, and the average N fertilizer loss rate of 38%, 29% and 20%, respectively. The NRE of F_LN₂₂₅ was significantly higher than F_LN₁₅₀ with no significant difference with F_M soils, while the NRE of F_HN₂₂₅ was significantly lower than F_HN₁₅₀. Increasing soil fertility significantly increased the contents of soil microbial biomass N, ammonium N, and fixed ammonium. 【Conclusion】 These results indicated that the higher of the soil fertility, the higher of the rice yield, the NRE and the N residual rate in the red paddy soil were, and the lower of the N loss rate was. Therefore, increasing N application rate was effective to increase both rice yield and NRE in low fertility soils. In contrast, an appropriate reduction in N application rate might benefit rice NRE and reduce fertilizer N losses without compromising rice yield.