节水灌溉减施磷肥对黑土稻作产量及土壤磷利用与平衡的影响

为探寻节水灌溉减施磷肥对黑土稻作磷利用及土壤磷平衡的影响，于2020年和2021年开展大田试验，以常规淹灌+常规施磷肥(CK，45 kg/hm2)作对照，节水灌溉模式下设置5个磷肥施用梯度：0（CP0，不施磷肥）、18 kg/hm2（CP1，减磷60%）、27 kg/hm2（CP2，减磷40%）、36 kg/hm2（CP3，减磷20%）、45 kg/hm2（CP4，常规施磷）。分析节水灌溉模式下减施不同程度磷肥对稻田产量、地上部植株吸磷量和土壤剖面各土层有效磷含量的影响，并计算土壤磷素表观平衡量和磷肥利用率。结果表明：2020年水稻收获后节水灌溉减施磷肥各处理表层土壤有效磷含量均显著低于CK处理的土壤有效磷含量（P<0.05）；2021年水稻收获后CP3处理表层土壤有效磷含量显著高于CK处理（P<0.05）。CP3处理2020年和2021年的地上部植株磷素积累量显著高于常规施肥CP4处理和CK处理，分别为14.64和15.86 kg/hm2（P<0.05）。地上部植株各器官磷素积累量由大到小为籽粒、茎鞘、叶。与常规施肥相比，2 a年CP3处理均显著提高了磷肥的吸收利用效率、农学利用率，显著降低土壤磷素盈余量（P<0.05）。综合考虑，节水灌溉下减施常规磷肥用量20%为黑土区适宜的磷肥施用量，2 a均提高水稻产量和磷肥利用率，且土壤磷素盈余量低。研究可为黑土区磷肥施用提供理论依据。

Effects of water-saving irrigation and reducing phosphorus fertilizer on rice yield, phosphorus utilization and soil phosphorus balance in black soil

Abstract: This study aims to explore the effects of water-saving irrigation and phosphorus fertilizer reduction on the phosphorus utilization of rice and soil phosphorus balance in the black soil region of China. A field experiment was carried out in 2020 and 2021. Compared with the conventional flooding irrigation and phosphorus fertilizer application (CK, 45 kg/hm2), five phosphorus fertilizer application levels were set under water-saving irrigation mode (C): 0 kg/hm2 (P0, no phosphorus fertilizer), 18 kg/hm2 (P1, 60% phosphorus reduction), 27 kg/hm2 (P2, 40% phosphorus reduction), 36 kg/hm2 (P3, 20% phosphorus reduction), and 45 kg/hm2 (P4, conventional phosphorus application). The balance of soil phosphorus and the phosphorus fertilizer utilization rate were calculated to determine the effects of phosphorus fertilizer reduction in different levels on the phosphorus uptake by aboveground biomass, rice yield, and available phosphorus content in the soil layer under water-saving irrigation. The results showed that the content of available phosphorus in the surface soil of water-saving irrigation and phosphorus fertilizer reduction treatment after harvest in 2020 was significantly lower than that of the CK treatment (P<0.05). The available phosphorus content in the surface soil of CP3 treatment was significantly higher than that of the rest under water-saving irrigation (P<0.05) after the rice harvest in 2021. All phosphorus reduction treatments under the water-saving irrigation in 2021 were significantly improved the content of soil available phosphorus in the 20-40 cm soil layer (P<0.05). The phosphorus accumulation in the aboveground biomass of CP3 treatment in 2020 and 2021 was significantly higher than that of CP4 and CK treatment, which were 14.64 and 15.86 kg/hm2, respectively (P<0.05). The phosphorus accumulation in each organ of the rice aboveground part was ranked in the order of the grain > stem and sheath > leaf. The phosphorus accumulation in the grain, stem, and sheath of CP3 treatment was significantly higher than that of the rest (P<0.05) in 2020 and 2021. The rice yield of the CP3 treatment was significantly higher than that of the CK treatment in 2020 and 2021 (P<0.05), the same as the CP4 treatment in 2021, whereas, there was no significant difference in 2020 (P>0.05). The rice yield of the CP3 treatment was the largest in the two-year experiment, which was significantly higher than that of the rest treatments (P<0.05). The two-year CP3 treatment had significantly improved the absorption and utilization efficiency of phosphorus fertilizer, as well as the agronomic utilization rate, indicating less surplus of soil phosphorus (P<0.05) in 2020 and 2021, compared with the conventional fertilization. Consequently, the 20% reduction of conventional phosphorus fertilizer application rate was optimal under water-saving irrigation in the black soil region. Therefore, the higher rice yield and phosphorus fertilizer utilization rate can be achieved in the two-year experiment, particularly for the less surplus of soil phosphorus.