The effects of phosphorus fertilizer and clipping on leaf growth and nutritional quality in 2 clones of Atriplex amnicola
2000
Islam, M. (Arid Zone Research Center, PARC, Quetta (Pakistan)) | Adams, M.A.
In a glasshouse experiment, we evaluated the effects of adding phosphorus (as superphosphate) and clipping (simulated grazing) on growth and nutrient content of foliage of two clones of Atriplex amnicola growing in a strongly P- fixing soil. Before clipping, leaf growth and N content, concentrations of soluble protein and chlorophyll, and phosphorus content increased linearly with the rate of P applied in both clones. Leaf re-growth after clipping was richer in N and soluble protein but poorer in chlorophyll and much poorer in P than before clipping. The "compensation" hypothesis suggests that the commonly observed increase in concentration of N in foliage after grazing as a result of re- mobilization of N from plant reserves or uptake from soil sources is an evolutionary advantage whereby photosynthetic capacity is rapidly increased and thus compensates for grazing losses. Such a hypothesis may well be untenable for p, particularly in plants with limited capacity for P-storage growing on strongly fixing soils, since new root growth is required to access the relatively immobile sources of P in the soil (in contrast with the greater mobility of N in soil) and the loss of P as well as photosynthetic area cannot be compensated.
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