Effect of phosphorus on yield components, plant height and grain yield, in wheat cultivars

Four experiments using the wheat cultivars: IAC-5 and Alondra-S-46 were carried out at Itararé Experimental Station in an acid soil showing low levels of phosphorus during the years of 1979 and 1980. The treatments consisted of five levels of P2O5 per hectare namely 0, 60, 120, 180 and 240kg. Grain yield increased with applied phosphorus for the two cultivars but IAC-5 showed higher yield and higher phosphorus efficiency in comparison with Alondra-S-46. Grain yield, spike length, number of spikelets per spike, number of kernel per spike, number of kernel per spikelet, 100 kernel weight and plant height for the cultivar , IAC-5 when levels of phosphorus were applied showed values significantly superior when compared with check. Considering the cultivar Alondra-S-46 the same conclusions were obtained for the following characteristics: head length, number of spikelets pet spike, 100 kernel weight and plant height. The cultivar IAC-5 presented grain yield for the different levels of P2O5 applied in the soil highly associated with all yield components under study, with plant height and with the amounts of P2O5 applied in the soil. Considering the cultivar Alondra-S-46 grain yield was highly correlated with head length, number of spikelets per spike, number of kernel per spike, 100 kernel weight and plant height, correlated with number of heads per linear meter and P2O5 levels applied in the soil and no association between grain yield and number of grain per spikelets was observed. Associations between levels P2O5 applied to the soil and phosphorus concentrations in the tops were highly significant for the two wheat cultivars under study.