Itthiphon khong chanit pui phosphate thimi phonto khwampen prayot khong that phosphorus naidin lae phonphalit khong phut nai rabop khao-thualuang thi pluk naidin chut Lampang.
1985
Wiroj Wajananawat
The results indicated no rice yield response to either form of phosphate fertilizer but showed a significant increase (P > 0.01) in the plant P-uptake levels and in the soil Bray II-P availability levels when applied with both forms of phosphated fertilizer. An increase in plant P-uptake between 1.8-2.0 times of the check treatment was observed from those plants applied with rock phosphate while only 1.1 time increase was observed from those applied with TSP (triple superphosphate). Significant increase (P > 0.01) in soybean seed yield with the application of superphosphate fertilizer was obtained. Seed yield increased from 78 kg/rai of the check to 227, 277 and 360 kg/rai of 3, 6, 12 kg P2O5/rai, respectively. Plant P-uptake also increased from 0.22 to 0.72, 0.98 and 1.67 kg P/rai, respectively. Only a mild response trend was observed from residual TSP application and no response was observed from those newly TSP application. The regression and correlation between P availability and seed yield and P-uptake could be expressed in equations as follows: Seed yield (kg/rai)= 80.63 + 15.01 (ppm-P Bray II), r=90**; P-uptake in seed (kg/rai) = 0.13 + 0.09 (ppm-P Bray II), r=86**. These results indicated that the application of rock phosphate to the rice crop could significantly increase the soybean yield in the rice-soybean cropping system on a naturally low-P content soil such as Lampang series.
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