Abstract
A study was carried out to determine the effects of rates and types of P fertilizer (SP-36 and Phosphate Rock) on the growth of physic nut (Jatropha curcas L.), leaf P content, and soil available P in an Ultisol in a glasshouse. The treatments consisted of four rates of P (0, 50, 100 and 150 mg P2O5 kg-1 soil) given in two different types of P fertilizer, namely SP-36 (total P2O5 = 36%) and Phosphate Rock (total P2O5 = 28%, particle size distribution = 75%<0.25 mm, 85%<0.50 mm, 90%<1.00 mm). Treatments were arranged in a Completely Randomized Design with three replications. The results showed that at the rates of 50 and 100 kg P2O5 ha-1, there was no difference in soil available P due to the application of SP-36 and Phosphate Rock, indicating that both types of P fertilizer had the same dissolution values after 8 months of P fertilizer application. At the rate of 50 kg P2O5 ha-1, the application of SP-36 and Phosphate Rock gave the same leaf P content. This could indicate that up to the first 8 months, the addition of the cheaper Phosphate Rock and the SP-36 to the soil had similar effectiveness. The response of tree biomass to P fertilization followed a quadratic pattern, in which for the application of Phosphate Rock, the P optimum rate was achieved at the rate which was lower than that for the application of SP-36. This suggests that the application of Phosphate Rock to physic nut trees was more efficient and effective compared to the application of SP-36.Keywords: Leaf P, phosphate Rock, physic nut (Jatropha curcas L.), soil available P, [How to Cite: Achmad AR. 2014. Influence of SP-36 and Phosphate Rock on Changes in Soil Available P, Leaf P Content, and Growth of Physic Nut (Jatropha curcas L.) in an Ultisol. J Trop Soils 19: 9-15. Doi: 10.5400/jts.2014.19.1.9]
Highlights
Previous researches showed that humic substance affect soil characteristic, water, and environment
The objective of the research was to evaluate the effect of humic substance addition, that was extracted from compost of rice straw, soybean straw, cassava starch solid waste and oil palm tree, to pH and Al suspension
The results indicated that Al chelation and precipitation by humic substance originated from some agricultural wastes compost can be used to control metal element on land metal-contaminated
Summary
Previous researches showed that humic substance affect soil characteristic, water, and environment. The role of humic substance in the soil that affect or control the metal activities and other pollutant (like pesticide) were studied by previous researchers, for example Cu (Karlsson et al 2008), Uranium (Singhal et al 2006), Hg and Pb (CruzGuzma et al 2003), and pesticide (Li et al 2003). Aluminum (Al) content in the soil is very high, but the solubility is very low. The Al solubility will increase as the soil acidity increase (Lindsay 1979). High Al concentration has a negative effect on plant root growth, and potentially retard nutrient absorbtion, like Mg (Sverdrup and Warfvinge 1993)
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