Proceedings: 2nd International Conference on Food and Agricultural Economics: EFFECT OF FERTILIZATION ON PHOSPHORUS UPTAKE IN COTTON

The aim of this research was to studythe effects of nitrogen and phosphorus fertilization on concentration and uptake of phosphorus in cotton (G. hirsutum L.), grown during 2012-2014 on Pellic Vertisols soil type in Chirpan, Bulgaria in crop-rotation with durum wheat under non-irrigated conditions. The experimental design was a randomized complete block with four replications. Single and combined nitrogen as NH4NO3 in rates 0; 80; 120 and 160 kg.ha-1 and phosphorus in rates 0; 80 and 120 kg.ha-1 were tested. It was established that fertilization with N120P80led to the highest economic effective yield – 1.82 t.ha-1, by 37.8% above the unfertilized. An alone phosphorous fertilization was not an efficient agronomic activity. Fertilization with P80 and P120 increases the phosphorus concentration in cotton plants. In bud formation an extremely high phosphorus content of 1.06% is reported at moderate levels N120P120 and the average phosphorus content is 0.82%. The P concentration in flowering stage is in the range of 0.67 (unfertilized) to 0.87% (P120 and N80P120). The phosphorus concentration decreases in maturity - average 0.53%. The phosphorus uptake depends on both the dry matter accumulation and the P concentration. The uptake of phosphorus averaged from 18.3 kg.ha-1 (N0P0K0) to 35.9-40.0 kg.ha-1 at high values of NP fertilization. The uptake was 24.5-25.6 kg.ha-1 at alone P rates. Nitrogen has a stimulating influence on the phosphorus utilization. At combined NP fertilization the P uptake increases significantly and at N160P120 reaches 40.0 kg.ha-1. P concentration and uptake went up with the increase of the phosphorus rate.