Soil Phosphorus Transformation And High-efficiency Utilization Of Phosphate Fertilizer For Sweet Corn In The Lateritic Red Soil Of Southern China

Developing sweet corn industry is important for optimizing corn industry in China.South China,an advantageous production region of sweet corn,is suffering from low P utilization efficiency because of readily absorption of phosphorus（P）by the Al/Fe-oxides in lateritic red soil.However,soil P pool has undergone tremendous changes and soil available P increased significantly after a long-term input of P fertilizer in the past few decades.Therefore,optimizing P fertilizer management strategies is needed to improving the P utilization efficiency（PUE）of sweet corn and realizing sustainable utilization of P rock resources.The aim of this study was to determine the effects of different P rates on sweet corn yield,P accumulation,PUE,P fractions in soil and P environmental risk in South China,to evaluate the agronomic,economic and environmental benefit of P building-up and maintenance technique（OPT）and organic manure partial substitution for chemical P fertilizer（OS）based on the“3+X”field experiments.The main results are as follows:（1）Phosphate fertilizer supply significantly increased sweet corn biomass and P accumulation.Compared with P0 treatment,the P accumulation of autumn sweet corn at jointing,silking and fresh-eating stage increased by 23.0%～79.7%,67.2%～94.7%,and 142.3%～214.0%,respectively,while increased by 64.0%～123.7%,85.3%～200.4%,and 105.8%～172.7%for spring sweet corn,respectively.The daily average P accumulation was highest from jointing stage to silking stage（0.41 kg P/hm²）and from silking stage to fresh-eating stage（0.34kg P/hm²）for autumn and spring sweet corn,respectively.Meanwhile,compared to P0 treatment,the yield in P1 treatment（37.5 kg P₂O₅/hm²supply）significantly increased by 23.2%and 132.5%for autumn and spring sweet corn,respectively,but not further increased with more P input.The PUE decreased gradually with P rates increased.The P uptake for autumn and spring sweet corn in P1 treatment were 17.88 kg P/hm²and 19.47 kg P/hm²,respectively.P accumulation of sweet corn ears from vegetation mass（stem,leaf,tassel）is less,while higher percentages for P accumulation after anthesis were observed for autumn（63.1%）and spring sweet corn（85.9%）.The P assimilation rate of sweet corn in spring was higher than that in autumn.（2）For each 100 kg P/hm²of P accumulated in lateritic red soil,Olsen-P increased by 12.25 mg/kg and 1.15 mg/kg,total P increased by44.36 mg/kg and 10.41 mg/kg,for the 0～20 cm and 20～40 cm soil layers,respectively.While the average soil inorganic P（Pi）fractions,including Sol-P,Al-P,Fe-P,O-P,and Ca-P significantly increased by 0.25mg/kg,16.22 mg/kg,22.08 mg/kg,2.04 mg/kg,and 5.08 mg/kg in the0-20 cm soil layer for each 100 kg P/hm²accumulation,respectively.Fe-P and Al-P become predominant P fractions with high P accumulation,and the concentration of Al-P would surpass Fe-P eventually.Pearson correlation coefficient showed a extremely significant positive relationship between Pi fractions and Olsen-P.Direct path coefficient from path analysis showed that Olsen-P can be influenced indirectly by Fe-P,O-P and Ca-P and affecting directly by Sol-P and Al-P,which can be regarded as the rapidly bio-availability P.With P accumulation in the soil,the availability of P and the environmental contamination increased simultaneously.The environment critical level of Olsen-P was 37.24mg/kg.The relationship between all Pi fractions and Ca Cl₂-P indicated that Sol-P had direct environmental leaching risk,while,while the environment critical level for Al-P and Fe-P were 74.70 mg/kg and 80.11mg/kg,respectively.（3）Under high soil available P conditon in lateritic red soil,compared to the farmer fertilizer practice（FFP）,the strategy of OPT and OS reduced the input of P fertilizer by 90.7%,but there was no significant difference between the yield,biomass and plant P accumulation of sweet corn.Both OPT and OS can significantly improved the PUE in the field experiments in Zhaoan and Langqi.The average ratio of economic output to input of OPT and OS increased by39.5%and 36.2%,respectively,while carbon emissions per a kilogram of yield reduced by 14.9%and 13.2%,respectively.In high P level lateritic red soil,Fe-P and Al-P were predominant P accumulation forms of soil inorganic P pool and Al-P was firstly used by sweet maize without P input.