Relationship Between Phosphorus Content Of Shoots And Phosphorus Uptake Of Arbuscular Mycorrhizai Fungi Under Condition Of Different Growing Density Of Maize

Improving soil P utilization efficiency for crop relied on arbuscular mycorrhizalsymbiosis is one of the effective way to solve the contradiction between supply anddemand of phosphorus in the agricultural system. However, the studies on phosphorusrequirement of shoots and phosphorus uptake of arbuscular mycorrhizal fungi undercondition of different growing density of maize, have not been reported. The fieldexperiment with maize (Zea mays L.) hybrid Zhengdan958was conducted at theDaxi experimental station of Jilin University in Changchun. The treatments consistedof two different crop densities (5×104plants/hm2,9×104plants/hm2). PVC pipes wereinserted around maize roots, and phosphorus depletion and hyphae length density ofsoil in the PVC compartment were determined to study the response of phosphorusuptake of arbuscular mycorrhizal fungi on phosphorus uptake under condition ofdifferent growing density of maize. Results and conclusions are as follows:1. Requirement of phosphorus, root colonization and hyphal length density wereimproved, independently of planting densities. That consequently reduced theconcentration of available P in rhizosphere and non-rhizosphere soil, and increasedthe shoot P content, which improved phosphorus uptake efficiency. These resultsindicate that AM fungi enhance the soil P utilization efficiency and increasephosphorus uptake efficiency of crop.2. The increment of extraradical hyphae of AM fungi in high planting densitysignificantly accelerated the soil P depletion compared with low planting density. Theresult suggests P uptake of maize is highly dependent on AM fungi in the modern highdensity planting patterns.3. In the treatments of high planting density, there were significant correlationbetween extraradical hyphae of AM fungi and soil P depletion in different soil layers (R2=0.550and R2=0.548), but not in low planting density treatments. The resultdemonstrates the more the hyphal length density obtains in different soil layers, themore the soil P will be depleted, as a consequence, the higher utilization efficiency ofphosphorus in the soil.4. The experimental results demonstrate that abundant hyphae were present inthe deep soil layer (60-80cm), and they accelerated the soil P depletion and thentransported the available P to the plants in order to improve yield.5. In situ, available P depletion in the topsoil (0-20cm,20-40cm) wassignificantly higher than those in deep soil layer (40-60cm,60-80cm) under highplanting density, but not in low planting density treatments. Even in deep soil layer(60-80cm), the soil P depletion was still high independently of planting densities,which demonstrates that AM fungi have great potential to the plants P uptake in deepsoil layer.