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