Influence of some controlled release nitrogen fertilizer treatments on the growth and nutrient composition of green bunching onions
1990
Isobutylidene diurea (IBDU), mixtures of plastic coated urea and ammonium nitrate, plastic coated urea, ammonium nitrate, and urea were evaluated as nitrogen sources for the production of green bunching onions grown on a Lakeland sand soil. IBDU was not an acceptable N source due to its slow release rate as indicated by the lower yield and leaf N content in comparison to the plastic coated urea, NH4NO3 and urea treatments. Treatments in which 50% of the N was from plastic coated urea and 50% from NH4NO3 resulted in yields similar to application of plastic coated urea at equivalent rates. Band application at planting of plastic coated urea (Escote 100) at 56 kg N/ha (50 lb N/A) produced a yield of marketable onions similar to three topdress applications of NH4NO3 or urea at 56 kg N/ha per application. However, 56 kg N/ha of Escote 100 costs about $25.00 per ha more than 168 kg/ha of ammonium nitrate or urea. This reduction by 112 kg N/ha for production of this crop would significantly reduce the potential for groundwater contamination by N. The benefits of plastic coated urea were more apparent when there were more leaching rains (>2.54 cm in 24 h) during the growing season.
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