Abstract:
The project entitled Critical analysis of the soil plant atmosphere continuum for increasing the productivity of rice in lateritic soils was conducted at two locations of Palakkad district (Koyalmannam and Ottappalam) for two seasons during 1999-2001. Objective of the study was to identify the role of P, K and lime in influencing the nutrient content of soil and plant and hence rice yield in Fe toxic lateritic solils .The study included the evaluation of influence of P, K and lime on macro and micronutrient content of soil and plant at critical stages in addition to uptake studies, correlation pattern of nutrient ratios with soil and plant was also studied.
Field evaluation of the crop performance at two locations revealed the following.
At Koyalmannam and Ottappalam P, K and lime significantly influenced the yield and yield contributing characters. Phosphorus, potassium and lime at 35 kg ha-1, 70 kg ha-1 and 600 kg ha-1 respectively increased the grain yield. However for the second crop at Ottappalam significant yield reduction was not observed even with the 17.5 kg ha-1 of P.
Pooled analysis of yield data showed significant influence of higher level of P at 35 kg ha-1. Potassium at higher level of 70 kg ha-1 significantly increased the yield. But higher level of lime application at 600 kg ha-1 significantly increased only the straw yield. However higher level of P, K and lime at 35, 70 and 600 kg ha-1 respectively increased the major nutrient content of the plant and decreased the Fe and Mn contents.
There was significant increase in the uptake of N, P and K while the Fe uptake was reduced by the higher level of K application. Potassium and phosphorus applied together in general decreased the Fe uptake while it enhanced the uptake of P and K.
Soil available major nutrients also showed significant positive response to higher level of K and lime application. There was an increase in the N, P and K contents of the soil at higher level of P application at 35 kg ha-1. The available Fe and Mn contents of the soil showed significant decrease at higher dose of K and lime.
Correlation studies showed significant positive correlation of N/Fe, P/Fe, K/Fe and K/Ca+Mg ratios of soil and plant with yield which indicated that an increase in P and K followed a decrease in the Fe content of soil which subsequently increased the yield.
