Effects of nitrogen forms on rhizosphere microorganisms and soil enzyme activity under cultivation of contrasting wheat cultivars Effects of nitrogen forms on nutrient uptake and growth of trees Tolerance of wheat genotypes to Al toxicity in relation to their rhizosphere pH change, NH4+ and NO3- uptake, and nitrate reduction under Al stress Effect of phosphorus application on soil available phosphorus and maize phosphorus uptake and yield Influence of Nitrogen Forms on Oat Growth and Phosphorus Uptake Effects of rhizosphere pH on utilization of P in phytin and lecithin by maize