重庆稻田基础地力水平对水稻养分利用效率的影响

【目的】土壤基础地力水平与土壤养分的供应能力有着直接的关系,进而影响作物对土壤和肥料养分的吸收。研究基础地力与水稻养分利用效率的关系,评价不同地力水平下水稻对土壤和肥料养分利用的影响,为在不同地力下提高养分利用效率提供依据。【方法】利用2006—2012年重庆测土配方施肥项目水稻"3414"试验,调查每个试验点无肥区(N0P0K0)、无氮区(N0P2K2)、无磷区(N2P0K2)、无钾区(N2P2K0)和全肥区(N2P2K2)处理的产量及秸秆和籽粒氮磷钾养分含量,计算重庆不同区域水稻养分吸收量、土壤有效养分利用效率和依存率以及肥料回收率、农学效率,采用指数及线性拟合、基础地力产量分级方法评价基础地力对水稻养分利用效率的影响。【结果】重庆不同区域稻田基础地力产量5.40—6.45 t·hm~(-2),基础地力等级处于低和中低等级的(4 t·hm~(-2)和4—5 t·hm~(-2))样本数为63,占总样本量的25.6%。随着稻田基础地力等级的提高,水稻产量和养分吸收量也随之不断增加,高基础地力等级稻田其有机质和碱解氮也相对较高,p H过低可能是低基础地力等级稻田(4 t·hm~(-2))的限制因素。重庆水稻施氮磷钾肥增产率分别为18.5%、5.2%和3.9%,在相同的施肥水平下,随着基础地力等级的提高,水稻氮磷钾肥料回收率分别下降6.9%、4.5%和3.1%。基础地力产量与土壤有效氮利用效率、土壤养分依存率存在正相关,说明较高的基础地力会促进水稻对土壤养分的吸收,提高土壤养分利用效率,而基础地力与氮肥回收率、肥料农学效率呈负相关,说明高基础地力会降低肥料的利用效率。基础地力与土壤有效磷、有效钾养分利用效率和磷钾回收率相关性不强,但与相应氮指标能够达到显著相关或极显著相关,说明基础地力对氮的反映能力高于磷钾。【结论】高基础地力可以提高水稻产量和对土壤养分的吸收量,但对肥料养分的利用效率下降。在高基础地力条件下,施肥对水稻的增产作用和地力提升作用有限,应限制肥料的投入。

Effect of Paddy Inherent Soil Productivity on Nutrient Utilization Efficiency of Rice in Chongqing

【Objective】The level of soil inherent productivity has a direct relationship with soil nutrient supply capacity, which affects the crop nutrient absorption of from soil and fertilizer. The objective of this research was to study the relationship between soil fertility and rice nutrient absorption efficiency and to evaluate its effect on rice nutrient absorption from soil and fertilizer under different soil inherent productivity levels, so as to provide a theoretical basis for improving rice nutrient absorption efficiency in different soil inherent productivity.【Method】Based on 246 rice “3414” trials in differentecological regions of Chongqing, including no fertilizer treatment (N0P0K0), nitrogen free treatment (N0P2K2), phosphate free treatment (N2P0K2), without potassium (N2P2K0) and total fertilizer treatment (N2P2K2), the rice yield and its grain and straw NPK content were investigated, and then rice nutrient uptake, soil available nutrient use efficiency and dependency ratio, fertilizer recovery, and agronomic efficiency were calculated. The effects of soil inherent productivity on nutrient absorption efficiency of rice were evaluated by means of index and linear fitting, soil inherent productivity and yield classification methods.【Result】The soil inherent productivity yield of paddy was 5.40-6.45t ·hm^-2 in different ecological areas of Chongqing, and the sample size of low and medium low (<4 t·hm^-2 and 4-5 t·hm^-2) was 63, accounting for 25.6% of the total sample size. With the improvement of paddy soil inherent productivity grade, nutrient uptake of rice was increased, and the organic matter and available nitrogen contents were relatively higher in the high soil inherent productivity grade paddy. Low pH might be a limiting factor for low base level rice fields (<4 t·hm^-2). The increasing rate of nitrogen, phosphate and potassium fertilizer in Chongqing was 18.5%, 5.2%, and 3.9%, respectively. Under the same level of fertilization, the recovery rate of NPK fertilizer was decreased by 6.9%, 4.5% and 3.1%, respectively, with the improvement of basic soil level. There was a positive correlation between inherent soil productivity and the use efficiency of soil available nitrogen and soil nutrient dependency rate, proving that higher inherent soil productivity could increase rice nutrient uptake and improve soil nutrient uptake efficiency. But the inherent soil productivity was negatively correlated with the apparent utilization rate of nitrogen fertilizer and agronomic efficiency of fertilizer, which showed that high inherent soil productivity would reduce the utilization efficiency of fertilizer. There was a weak correlation between soil fertility and available P, K as well as the apparent utilization of them. However, the inherent soil productivity was significantly correlated with the corresponding nitrogen index, proving the reflective ability of inherent soil productivity on nitrogen was stronger than that on P and K.【Conclusion】High soil inherent productivity can improve rice yield and soil nutrient uptake, but reducing the utilization efficiency of fertilizer nutrient. Under the condition of high soil inherent productivity, fertilization has limited effect on rice yield increase and soil productivity improvement, so the input of fertilizer should be limited.