The effect of phosphate rocks, triple super phosphate and their combinations on the performance of Sorghum bicolor var. dura (L.) x sorghum Sudanese (piper) (stapf) [Sudan]

A three season field trial tested the effects of phosphorous fertilizer on fodder sorghum pioneer 988. Two types of phosphate rocks (Uro and Kurun) were included along with the triple super phosphate together with basal nitrogen. These sources of phosphorous were applied at different rates, namely, 0, 200 and 300 Kg/feddan for triple super phosphate and 0, 80 and 160 Kg/feddan for phosphate rock singly or in combinations. The experiment was carried out in the top farm, University of Khartoum at Shambat and run for three successive seasons. The experiment was arranged in a factorial randomized complete block design with three replicates. Plant samples were collected twice. Growth parameters measured included: plant height, fresh and dry yields. Leaf area index, leaf contents of nitrogen, phosphorous, potassium, calcium, magnesium and sodium were measured. The records obtained showed that the highest combinations of triple super phosphate and phosphate rocks increased plant height from 110 cm to 145 cm. The dry matter yield was significantly increased by the treatments. The increment in the dry matter yield was 350 Kg/feddan in the control to 490 Kg/feddan for the combination. The results obtained from the phosphate rocks treatments were almost similar to those of the triple super phosphate. The best residual effect was obtained from (1200 TSP + 640 Uro) and (800 TSP + 320 Kurun). Soil analysis carried out at harvest indicated significant influence of the applied phosphate fertilizers on the soil reaction. The soil pH was clearly affected by the highest rate of phosphate fertilizer. It was reduced to 6.2 with that of the control which was 8.0. Electrical conductivity of saturation extract (ECe) was also affected significantly (P+ or - 0.01). It decreased by the application of the fertilizer from 5.17 ds/m to 2.98 ds/m. Soluble cations were insignificantly affected by different treatments. Available phosphorous recorded a measurable increment from 0.78 mg/1 for the control treatment to 1.55 mg/1 for the highest combination.