Wheat Growth-Induced Changes in Phosphorus Pools in the Crop Residue Detritusphere Are Influenced by Residue C/P Ratio

This experiment was carried out to elucidate the effect of residue C/nutrient ratio on P pools and N availability in wheat rhizosphere. The microcosms included an upper and a lower PVC core with one end of both cores covered by nylon mesh. Wheat was planted in the upper core. To the lower core, crop residues were added as a thin uniform layer on the top mesh. Treatments were control without residue or wheat growth, wheat growth without crop residue, barley straw without or with wheat growth, and barley faba bean residue without or with wheat growth. Sampling was carried out after 14 and 28 days in wheat rhizosphere alone, detritusphere of faba bean residue and barley straw, and in the rhizosphere/detritusphere interface. Mass loss of low C/P faba bean residue was greater than of high C/P barley straw; and mass loss was greater in the detritusphere alone than in the rhizosphere/detritusphere interface. Plant P concentration and P uptake were higher with faba bean residue than with straw and unamended wheat plants. With faba bean, most P pools and N availability, but not microbial biomass N and P, were lower in the rhizosphere/detritusphere interface than detritusphere alone. P pools were higher in detritusphere of faba bean residue than wheat rhizosphere alone. With straw, P pools and MBN were low and not affected by wheat roots. P pools and N availability in the wheat rhizosphere/detritusphere interface were influenced by residue type, and plant nutrient uptake reduced P pools and available N only with low carbon/nutrient faba bean residue.