| New advances for theory and techniques of regional fertilizer recommendations will be needed to reconcile contradictions between decentralized management mode of small farmers and large-scale industrial production of fertilizer. Based on the regionalization of fertilization for maize, wheat and rice production in China, the grain yield response to phosphorus (P) and potassium (K) and major influence factors across major agro-ecological regions of maize, wheat and rice production in China were analyzed, regional optimal rates of P (based on P building-up and maintenance approach) and that of K (based on yield response to K application) in each sub-region were estimated. Then, according to the approach of "regional fertilizer formula plus site specific adjustment"(RFF&SSA), regional optimal compound fertilizer formulae were determined. Finally, we comprehensive evaluated the agronomic and economical effects of this approach through178on-farm experiments. The main results were concluded as follows:(1) A total of7081,4232and9608on-farm experiments, conducted during2005-2010across major agro-ecological regions of maize, wheat and rice production in China, were analyzed for determining the yield response to P. The results indicated that application of P increased the yield of the three crops significantly, compared to zero P fertilization (P0). Phosphorus application in wheat had the highest potential to increase yield (the average of increased yield (rate), relative yield and agronomic efficiency of applied P (AEP) were0.9t ha-1(18.8%),85.8%,8.8kg kg-1, respectively), followed by maize (the average of increased yield (rate), relative yield and AEP were1.1t ha-1(15.7%),88.0%,12.4kg kg-1, respectively), the lowest was rice (the average of increased yield (rate), relative yield and AEp were0.8t ha-1(12.8%),89.9%,13.1kg kg-1, respectively). Crop yield response to P varied widely in differently agro-ecological regions. Maize yield response to P in the Northeast China, Northwest China and Southwest China were higher than that of North China Plain; Wheat yield response to P in the North China Plain was slightly lower than others; Rice yield response to P in Northeast China and Yangtze River were higher than that of South China and Southwest, Early rice response to P was higher than that of Late rice in Yangtze River. The results showed that, with the increasing soil-P level, crop yield response to P decreased. Grain yield response to P were also affected significantly by crop production system, especially by temperature and moisture.(2) A total of3124,3924and9490on-farm experiments conducted during2005-2010across major agro-ecological regions of maize, wheat and rice production in China, were summarized and analyzed to determine the yield response to K. The results indicated that maize grain yields at recommended K rates increased14.0%,14.7%,19.4%, and4.3%in Northeast China, North China Plain, Southwest China, and Northwest China, respectively, compared to zero K fertilization (K0). Nationally, increased yield (rate) of wheat due to K application averaged0.7t ha-1(12.5%), and the corresponding relative yield and agronomic efficiency of applied K (AEk) were90.0%,7.2kg kg-1, respectively. The increased yield (rate) of rice due to K application averaged0.81ha-1(12.5%), and the corresponding relative yield and AEK were90.1%,9.1kg kg", respectively. The yield response to K was only partly related to soil extractable K (NH4OAc-K), which were affected significantly by site properties (such as counties, varieties, soil types or years). The results showed that, with the increasing grain yield level, crop yield response to K increased.(3) Using the955measurements in44on-farm experiments and the953measurements in56on-farm experiments, the P and K requirement per ton grain yield in the optimal NPK treatment for summer maize in the North China Plain (NCP) was3.20kg and15.0kg, respectively. In the Optimal P treatment, with the increasing yield levels, P requirements decreasing which was attributed to a decline in grain P concentration and an increase in harvest index. The relative consistency of K requirements with increasing grain yield was mainly attributed to an offset in the increase in stover K (from14.0to18.1g kg-1), an increase in harvest index (HI) from0.49to0.54, and the stability of grain K concentrations (about3.2g kg-1).(4) Optimal rates of P (based on P building-up and maintenance approach) and K (based on yield response to K application) were estimated in each sub-region for maize, wheat and rice. Across all the12maize sub-regions, the optimal rate of P averaged75kg P2O5ha-1(ranged from46to123kg P2O5ha-1) and the optimal rates of K averaged54kg K2O ha-1(ranged from30-64kg K2O ha-1); Across all the7wheat sub-regions, the optimal rates of P averaged77kg P2O5ha-1(ranged from55to88kg P2O5ha-1) and the optimal rates of K averaged50kg K2O ha-1(ranged from33-59kg K2O ha-1); Across all the8rice sub-regions, the optimal rates of P averaged71kg P2O5ha-1(ranged from59to84kg P2O5ha-1) and the optimal rates of K averaged62kg K2O ha-1(ranged from45to80kg K2O ha-1).(5) Given variation in optimal nutrient rates, climate, crop production and soil types among different agro-ecological regions, a total of16region-specific fertilizer formulae were designed for the12sub-regions of maize production in China, including12formulae using a basal plus top-dressing fertilization approach and4formulae using only basal fertilization application; a total of9regional special fertilizer formulae were designed for the7wheat sub-regions in China, including7formulae using a basal plus top-dressing fertilization approach and2formulae using only basal fertilization application; a total of11regional special fertilizer formulae were designed for the8rice sub-regions, including7compound fertilizer formulae with high nutrient concentration and4with medium concentration.(6) A total of178on-farm experimental sites conducted during2011-2013across major agro-ecological regions of maize, wheat and rice production in China were evaluated the approach of RFF&SSA. Compared to the farm practice, the yield of maize (n=63), wheat (n=36) and rice (n=79) using the RFF&SSA can be increased9.0-11.4%,7.6-11.7%and8.3-10.5%, respectively; the PFPN can be increased by18-22%,29-35%and42-48%, respectively; the income per hectare can be increased by1255-1433Yuan,1476-1688Yuan and2044-2388Yuan, respectively;... |
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