Differential response of soybean genotypes to soil pH and manganese application

An experiment was conducted at Tamil Nadu Agricultural University, Coimbatore, India during 1982 wet season (June–July) to study the root activity and rooting pattern of IR-20 rice as influenced by urea insecticide combinations by a³²P absorption technique. The treatments involved a factorial combination of four levels of N (0, 60, 90 and 120 kg N/ha) as urea and three levels of insecticides (no insecticide, carbofuran @ 0.75 kg a.i./ha and phorate @ 1.0 kg a.i./ha). The root activity measured in terms of the amount of³²P absorbed by the plant, increased considerably by the application of urea and insecticides (carbofuran or phorate) as well as due to their interactions. The root activity increased upto 120 kg N ha⁻¹. Carbofuran or phorate application increased root activity and the effect of carbofuran was greater than that of phorate. Nitrogen-insecticide interaction was positive on root activity upto 120 kg N ha⁻¹ and the effect was more marked with carbofuran and N combinations. But the percentage distribution of active roots of rice could not be influenced by levels of N, insecticides or their interactions. About 80 percent of the roots of IR 20 rice forage within 10 cm from the surface. The enhanced root activity due to application of N and insecticides (carbofuran and phorate) increased the uptake of major and micro-nutrients. the phytotonic effects of carbofuran and phorate on rice works by triggering the root activity of the crop.