Evaluation of Boron Produced As Seed-Core Urea for Urease Inhibition
Loading...
Date
2013-11
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Borax (Na2B4O7.5 H2O) and boric acid (H3BO3) were evaluated as urease inhibitors by quantifying ammonia (NH3) volatilization loss under upland and flooded conditions. Boron-enriched urea was produced by two methods – compaction/tableting and seed-core granulation. The NH3 losses from the B products were compared with urea, urea + N-(n-butyl) thiophosphoric triamide (NBTPT) and urea + cyclohexyl phosphoric triamide (CHPT). The greenhouse study was conducted over a 17-day period and a 25-day period for the upland and flooded soils, respectively. The following year the experiment was repeated using freshly made and original products. Ammonia volatilization loss was a major N loss pathway under both the upland and flooded conditions accounting for losses of 34% and 51% of applied urea-N, respectively under the conditions of the experiment. The method of production of urea products containing B did not influence the NH3 volatilization loss. All B seed-core urea products were effective in reducing ammonia volatilization losses; however, when compared with urease inhibitors, NBTPT and CHPT, they were less effective. Under the upland condition, B seed-core urea gave as much as 37% lower NH3 volatilization loss than urea during the first 5 days, compared to only 17% lower volatilization loss after 17 days. Similar results of 37% and 10% lower NH3-N losses were obtained with flooded soil for first 5 days and after 15 days, respectively. Throughout the entire experimental period, losses of ammonia from soil treated with B seed-core urea were significantly lower than losses of ammonia from the same soils with urea applied alone. While there was no decline in the effectiveness of B seed-core urea products, the NBTPT product showed significant loss of activity during the 12-month storage period. Among the B products 0.5% B as boric acid was as effective as 2% B as borax in reducing volatilization losses. The single high rate of urea-N application (200 kg N ha-1) and the absence of a crop in this study may have influenced the effectiveness of B as a urease inhibitor, and most likely resulted in higher ammonia volatilization loss.