Increase in soil pH by liming has been considered sufficient to assure Mo availability for crops. In soybean, the high response to liming might be related to additional demand of Mo for nitrogenase complex activity, in relation to other non-nitrogen fixing crops. Therefore, this research planned to study lime-Mo interactions for soybeans and sorghum crops, in a Red-Yellow Podzolic soil from the Mococa Experimental Station, Instituto Agronômico, State of São Paulo, Brazil, during the period 1985 to 1989. The treatments were set up in a randomized complete block design, with four replications, in a split-plot experiment. The main plots received 0, 2, 4, 6 and 8 t ha-1 of limestone and the subplots received annually 0, 50 and 100 g ha-1 of Mo applied on the seeds as ammonium molybdate. There were three soybean croppings of IAC 11 cultivar, intercalated with one of grain sorghum (DK 64 cultivar). High yield responses to liming were observed for all crops and for both species. Mo application decreased the response of both crops to liming, which indicated that liming can be replaced by Mo. The soybean responses to Mo were more evident without liming, whereas that of sorghum was more evident, with the intermediate rates of liming. Responses to Mo occurred for soil pH (CaCl2) at values below 5.2. It was concluded that higher soybean yields require higher soil acidity neutralization and that it is possible to reduce lime requirement to reach maximum yield by the application of Mo in the seeds, for both species, especially in an acid soil with low available Al and Mn.
micronutrients; soybean yield; acid soil; seed treatment