Abstract
The effect of rate and method of urea application on the yield of common beans (Phaseolus vulgaris L., cv. IPA-1) was evaluated on a Red-Yellow Latosol (Psamentic Haplortox) of Arapiraca and on a Solodic Planosol (Ustalf) of Igaci, both sandy-clay-loams located in the State of Alagoas, Brazil. Rates of 30,60 and 90 kg N/ha were applied placing the urea totally in the furrow at planting time; totally sidedressed twenty days after planting, mixed or not with the soil; or 1/3 of the amount in the furrow at planting plus 2/3 sidedressed twenty days after planting, mixed or not with the soil. Bean yield responses to nitrogen followed quadratic equations. In the Red-Yellow Latosol response to nitrogen occurred up to the rate of 66 kg N/ha, while in the Solodic Planosol the yield increased up to the highest applied rate of 90 kg N/ha. The relative yield increase for each site was 22% and 16%, respectively. Sidedressed application of the total amount of urea resulted in the lowest yields, whereas split application and furrow fertilization were the best and equally effective methods. No significant yield increase was observed by mixing the urea with the soil.
Highlights
Use of urea as a nitrogen source for crops has substantially increased in Brazil during the last fifteen years
The interaction "rate of urea x method of application" was not significant in the experiment conducted on the Red-Yellow Latosol, but bean yield in this site increased with the applied rate of urea according to a quadratic equation (Figure 1)
Response to nitrogen application occurred up to the rate of 66 kg N/ha, which corresponded to a maximum yield of 2.53 t/ha of beans, a yield increase of 463 kg/ha (22%) over the control treatment
Summary
Use of urea as a nitrogen source for crops has substantially increased in Brazil during the last fifteen years. Reliable information on the amount and methods of urea application to the various crops cultivated under the extremely different climates of Brazil are rare or even absent. Considering that the proportion of experiments with positive responses of beans to nitrogen application in our country is around 30% (IGUE, 1968 and MALAVOLTA, 1972), it is possible that the demand of additional amounts of nitrogen in the soil by this crop is not high. Several experiments were carried out in different regions of Brazil to study the effect of rates, methods and time of urea application on the yield of cotton (KIEHL et al, 1985) and corn (MELLO et al, 1988).
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