Abstract
To examine the effect of NPK application on the growth, yield and nutrient uptake by sugarcane (Saccharum officinarum L.) and to elucidate the limiting factors of cultivation on sandy soils in the tropics, a field experiment was carried out in 2005 on a sandy soil in Khon Kaen, Northeast Thailand. Six treatments were applied: NPK (300 kg ha-1 each), PK, NK, NP, control and NPK+manure (300 kg ha-1 each + 30 t ha-1) treatments. Plants were harvested and the dry weight, yield and NPK contents determined. Root distribution in the soil profile was also examined. Aboveground biomass values in the PK, NP, NPK and NK treatments were 26, 37, 85 and 87% higher than in the control (31.4 t ha-1), respectively, indicating that N was the dominant limiting factor, followed by K, with little effect of P. Aboveground biomass value in the NPK + Manure treatment was not significantly different from that of the NPK treatment, suggesting that the advantage of organic matter application was limited in the present study. More than 80% of the roots were distributed within the surface 30cm. Nutrient removal in the control treatment amounted to 39 kgN ha-1, 12 kgP ha-1 and 39 kgK ha-1, which corresponded to 83, 5 and 15% of the soil available nutrients. In conclusion, adequate N and K fertilization in combination with effective erosion control to conserve surface soil would be essential for sustainable production of sugarcane on sandy soils in the tropics.
