湖北省不同稻作区域秸秆还田替代钾肥效果

【目的】研究不同稻作区域钾肥和秸秆还田对水稻产量、钾素吸收量以及农田钾素表观平衡的影响,分析不同稻区秸秆还田可替代化学钾肥的用量,为不同区域稻田秸秆还田条件下钾肥的合理配置提供理论依据。【方法】2013年在湖北省鄂东丘陵、鄂中丘陵岗地和江汉平原3个区域的19个县(市)布置稻田秸秆还田替代钾肥效果研究田间试验,试验共设置6个处理:分别为(1)不施钾(NP);(2)施化学钾肥(NPK);(3)施秸秆(NP+S);(4)秸秆还田配施1/2化学钾肥(NP+1/2K+S);(5)秸秆还田配施3/4化学钾肥(NP+3/4K+S);(6)秸秆还田配施全量化学钾肥(NPK+S)。【结果】不同稻作区钾肥和秸秆均能不同程度增加水稻产量和地上部钾素吸收量。与NP处理相比,鄂东丘陵区、鄂中丘陵岗地区和江汉平原区NPK处理水稻分别增产0.36、0.36和1.07 t·hm-2,平均增产率分别为6.4%、5.0%和15.3%;而施秸秆(NP+S)处理水稻分别平均增产0.57、0.49和0.24 t·hm-2,增产率为7.6%、6.9%和4.0%。3个稻作区施化学钾肥(NPK)地上部钾素吸收量平均增加20.1—61.9 kg K2O·hm-2,施秸秆(NP+S)钾素吸收量平均增加8.5—39.1 kg K2O·hm-2,江汉平原区施化学钾肥处理产量和钾素吸收量均显著高于施秸秆处理,而鄂东丘陵区和鄂中丘陵岗地区NP+S与NPK处理的产量和钾素吸收量均没未表现出差异。通过计算土壤-作物系统钾素表观平衡,发现一季水稻收获后土壤钾素均处于亏缺(平均钾素亏缺量为144.3—284.4kg K2O·hm-2)状态,但秸秆还田处理亏缺量小于秸秆不还田处理。在保证水稻产量(即NPK处理产量)时秸秆还田条件下,采用模型计算出鄂东丘陵区、鄂中丘陵岗地区和江汉平原区的平均钾肥用量分别比目前钾肥推荐用量(60kg K2O·hm-2)节约化学钾肥66.8%、75.2%和9.7%;参考2013年钾肥和水稻价格,可计算出秸秆还田条件下鄂东丘陵区、鄂中丘陵岗地区和江汉平原区最经济钾肥推荐用量分别比推荐用量节省化学钾肥54.3%、53.5%和36.9%。【结论】湖北省不同稻区均可采用秸秆还田的方式减少钾肥投入,不但可以缓解土壤钾素亏缺,而且对农田钾素的可持续管理具有重要意义。

Effect of the Substitution of Straw Incorporation for K Fertilization in Different Rice Producing Regions of Hubei Province

【Objective】The experiment was conducted to study the effects of potassium (K) fertilization and straw incorporation on rice yield, K uptake and K balance in different rice producing regions of Hubei province, in order to find how much chemical potassium can be replaced by straw potassium. The results would provide a scientific basis for K fertilization management under straw incorporation for different regions. 【Method】Field trials in 19 counties were carried out to study the effects of the substitution of straw incorporation for K fertilization in hilly regions of east (HEH) and center Hubei (HCH) and Jianghan Plain (JHP) in 2013. The designed six treatments were no K fertilization (NP), chemical K fertilization (NPK), straw incorporation (NP+S), straw incorporation with 50% of chemical K fertilizer (NP+1/2K+S), straw incorporation with 75% of chemical K fertilizer (NP+3/4K+S), and straw incorporation with 100% of chemical K fertilizer (NPK+S). 【Result】Both K fertilization and straw incorporation improved the rice yield and K uptake across the regions. Compared with NP treatment, the averaged rice yield increased by 0.36, 0.36 and 1.07 t·hm^-2 in NPK treatment in the regions of HEH, HCH, and JHP, respectively, with the increasing rate of 6.4%, 5.0% and 15.3%. For the NP+S treatment, rice yield increased by 0.57, 0.49 and 0.24 t·hm^-2 in HEH, HCH, and JHP regions, with the increasing rate of 7.6%, 6.9% and 4.0%, respectively. K fertilization (NPK) enhanced the K uptake by 20.1-61.9 kg K₂O·hm^-2, while the straw incorporation (NP+S) increased K uptake by 8.5-39.1 kg K₂O·hm^-2. Both yield and K uptake of NPK treatment were higher significantly than NP+S treatment in JHP area. However, no difference was observed between the NPK and NP+S treatments in the HEH and HCH areas. After calculating the apparent K balance, it was found that K lost (144.3-284.4 kg K₂O·hm^-2) occurred in all the treatments across the sites especially in the treatments without straw incorporation. Model was used to fit the relationship between K fertilization rate and rice yield, the optimum application rate of K fertilizer under straw incorporation for which could reach the yield under NPK treatment was obtained. The optimal K rate was 19.9, 14.9 and 54.2 kg K₂O·hm^-2 in the regions of HEH, HCH, and JHP, which saved chemical K fertilizer by 66.8%, 75.2% and 9.7% compared with the recommended amount (60 kg K₂O·hm^-2), respectively. Using the price of K fertilizer and rice in 2013, the economic optimum K rate (EOKR) could be obtained. The EOKR values were 27.4, 27.9 and 37.9 kg K₂O·hm^-2 in the HEH, HCH, and JHP, saved 54.3%, 53.5% and 36.9% chemical K fertilizer compared with the recommended amount, respectively. 【Conclusion】Chemical K fertilizer could be partly replaced by straw incorporation across different rice planting regions in Hubei province. In addition, straw incorporation can alleviate soil K loss, which plays an important role in sustainable potassium management on farmland.