The effects of decomposing roots on the growth of grassland plants.
Anthoxanthum odoratum, Holcus lanatus, Hypochoeris radicata, Lolium perenne, Plantago lanceolata and Rumex acetosa ('treatment' spp.) were grown separately on a nutrient-poor soil and their roots were left to decompose. Each sp., except for H. lanatus and H. radicata, was then grown as a 'test' sp. on the soils where those roots had decayed, so that there were all combinations of 'treatment' spp. and 'test' spp. The growth and nutrient uptake of plants was measured. The roots of R. acetosa had the greatest inhibiting effect on the growth of the 4 spp. when decomposition occurred in water-saturated soil, but not in moist soil (field capacity) nor in dry soil. P was deficient when decomposition had occurred in wet soil. The uptake of P by the following 'test' spp. was negatively correlated with the amount of P removed in the shoots of the previous 'treatment' spp. The growth rate of 'test' spp. was greater after decomposition in dry soil than in wet soil. P was less limiting after decomposition had occurred in dry soil, and the P conc. in the shoots of the 'test' spp. was then positively correlated with the amount of P in the roots of the treatment spp. before decomposition. The effect of decomposing roots on the subsequent growth of plants appeared to depend mainly upon the P content of the decomposing roots, the m.c. of the soil during decomposition and the interaction of these 2 factors.