EFFECT OF LIMING AND MICRONUTRIENT APPLICATION ON THE GROWTH AND OCCURRENCE OF STERILITY IN MAIZE AND TOMATO PLANTS IN A MALAYSIAN DEEP PEAT SOIL

Two field experiments were conducted in a deep woody peat soil located at Pontian in the south western part of Peninsular Malaysia to determine the effect of graded levels of liming with and without micronutrient application on the growth and performance of maize and tomato plants. The results obtained revealed that the growth of the maize and tomato plants was extremely poor in the unlimed treatment (pH 3.8 to 4.0). When micronutrients were applied, the growth was enhanced and the yield increased with the increase of the lime level and reached a maximum value at the lime level of 8 t/ha (pH 5.0 to 5.3) in both plants. There was no difference in the yield above the lime levels of 8 t/ha. When micronutrients were not applied, shoot growth of maize was enhanced with the increase of the lime level up to 8 t/ha in the same manner as in the treatments with micronutrient application. However, grain formation was inhibited while in the case of tomato the shoot growth was extremely inhibited and no fruits were formed regardless of the lime levels. The inhibition of grain formation in maize was much more severe both in the lower and higher pH ranges than in the intermediate pH range. Furthermore, shoot growth of tomato was also more severely inhibited both in the lower and higher pH ranges. Contents of Cu and B of both crops were critically low for the deficiencies in the treatments without micronutrient application. In order to analyze the behavior of the micronutrients in relation to the pH in this peat soil, an incubation study was conducted. The contents of 0.1 m HCl extractable Fe, Mn, Zn, and Cu and hot water soluble B decreased with the increase of the pH from 3.5 to about 7.0. The amount of ammonium oxalate extractable Mo increased with the increase of the pH up to pH 4.7, but it decreased with the increase of the pH above 4.7. It was suggested that the growth inhibition and the occurrence of sterility in the treatments without micronutrient application were caused by the deficiencies in Cu and/or B.