Cassava Response to Phosphorus Fertilizer in Warin Soil Series Amended with Cassava Tails and Stalk-Bentonite Mixture.

A field experiment was conducted in a farmer field in Nakhon Ratchasima province, northeast, Thailand objectively to investigate the response of cassava, Huay Bong 80 variety to phosphorus (P) fertilizer in Warin soil series (classified as Grossarenic Paleustults) amended with cassava tails and stalk (CTS) mixed with bentonite (BTN). The experiment was arranged in split plot with four replications. Main plot consisted of four rates of CTS +BTN: 0+0, 6.25+1.25, 12.5+2.5 and 25+5 t/ha while subplot comprising four rates of P fertilizer: 0, 25, 50 and 100 kg P2O5/ha. Cassava was harvested at 12-month of age and plant samples were collected at the harvesting time to study the effects of soil amendment on the uptake of primary plant nutrients in different plant parts of cassava. The results showed that the CTS+BN mixture at the rate of 25+5 t/ha highly significantly promoted the highest fresh tuber yield (FTY) and starch yield (SY) of 31.79 and 8.97 t/ha, respectively, which were 21.2 and 20.7 % greater than that of the control with no soil amendment addition. Increasing rate of P fertilization highly significantly induced greater FTY, SY and aboveground biomass (ABG) than did the zero-P fertilization. Amending the soil with 25+5 t/ha of CTS+BN along with the addition of 100 kg P2O5/ha interactively gave the significantly highest respective FTY, SY and ABG of 39.76, 11.48 and 17.35 t/ha whereas the plot amended with 12.5+2.5 kg CTS+BN/ha plus 50 kg P2O5/ha fertilization gave slightly lower STY and SY of 36.11 and 10.30 t/ha, respectively. The former combined rate of soil amendment and P fertilizer also had the interaction that highly significantly induced the highest uptake of all primary plant nutrients in the whole plant, accounting for 131.66, 14.23 and 124.13 kg/ha of respective nitrogen, phosphorus, and potassium. The result reaffirmed that amending the soil with proper rate of CTS+BTN mixture enhanced the efficiency of P fertilizer and subsequently improved yield of cassava. [ABSTRACT FROM AUTHOR]

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