Grain P concentrations,P allocation and internal use efficiency of maize affected by P application and intercropping

The aim of this study was to investigate the influences of phosphorus(P)fertilizer application and intercropping on maize grain P concentrations,harvest indexes,P harvest indexes and internal P use efficiency of maize plants.Field experiments were carried out in 2009,2010 and 2011.The main plots received pure P applications of 0,40 and 80kg/hm2,and the sub-plots comprised maize monoculture and maize(Zea mays L.cv.Zhengdan no.958)intercropping with oilseed rape(Brassica napus L.cv.Longyou no.1)in 2009 or turnip(Brassica campestris L.cv.Gannan no.4)in 2010 and 2011,faba bean(Vicia faba L.cv.Lincan no.5),chickpea(Cicer arietinum L.cv.Longying no.1)and soybean(Glycine max L.cv.Huaxia no.1 in 2009 and cv.Wuke no.2 in 2010 and 2011),respectively.1)Intercropping significantly enhanced maize grain P concentrations compared to monocropped maize,the average grain P concentrations of maize intercropped with Brassica,faba bean,chickpea and soybean were increased by19.8%,13.0%,17.2% and 12.0%,respectively.However,neither the harvest indexes nor the P harvest indexes of maize were influenced by intercropping.This indicates that the allocation of dry matter and P in vegetative tissues and grains at maize harvest were not influenced by intercropping.Further studies showed that internal P use efficiency of maize plants intercropped with Brassica,faba bean,chickpea and soybean were significantly reduced by 15.9%,9.6%,14.9% and 8.5%,respectively.2)No responses of harvest index of maize to P were found in all the three years.In 2009,there were no significant effects of fertilizer P application rates on the average maize grain P concentrations.Afterwards,the average grain P concentrations in 2010 and 2011 were all significantly increased by average of 12.5% at P 40kg/hm2 and 15.9% at P 80kg/hm2 compared to no P application;meanwhile,the internal P use efficiency of maize plants at P 40kg/hm2 in 2010 and at P 80kg/hm2 in both 2010 and 2011were significantly decreased by 8.8% and 10.4%,respectively;the P harvest indexes were enhanced by P only in 2011.In general,both intercropping and P application increased maize grain P concentrations while decreased internal P use efficiency with luxury absorption of P and P application enhanced the P harvest index of maize.