Optimization of the efficiency of phosphate fertilizers in acidic-ferralitic soils of the humid tropics.
2000
Getachew Agegnehu and Sommer,K.(Researchers)
A greenhouse experiment was conducted to investigate the availability of phosphorus fertilizers to maize (cv. Golda FAO-240) on a Liberian acidic-ferralitic soil. The soil was limed uniformly with 1.05 g of Ca(OH)2 and 1.220 g of CaSO4. 2H2O/1.7 kg soil according to Jensen curve. Phosphorus was applied as mono-ammonium and calcium hydrogen phosphate at the rates of 0, 26 and 52 mg P/a.7 kg soil by broadcast and placed (depot) application using soil, neutral soil and neutral compost as buffering materials. Nitrogen was applied at planting as ammonium nitrate and urea and as top-dressing as calcium nitrate three weeks after planting. Potassium, Mg and microelements (Cu, Zn, B and Mo) were applied uniformly to all pots. Placed application of 52-mg phosphorus/1.7 kg soil in pot at a depth of 10 cm in the form of NH4H2PO4 mixed with neutral compost increased nutrient uptake and shoot dry-matter yield. The shoot dry-matter yield (9.6 g) was almost doubled and phosphate uptake (22.0 g) was tripled over the control (5.3 and 7.4 g), respectively. Ammonium nitrate treated plants exhibited higher shoot dry-matter yield and higher uptake of P, K and Mg as compared to urea regardless of rate and method of application. The shoot dry-matter yields of plants were correlated with plant height and uptake of P, K and Mg (r=0.92**, 0.93**, 0.99** and 0.93**, respectively). The results of this investigation showed that increased dry-matter yield and higher nutrient uptake by plants were accompanied with lower nutrient concentrations in soil.
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