Agronomic evaluation of control-release urea (CRU) in some crops in Inner Mongolia

The purpose of this study was to demonstrate the appropriate ratio of controlled-release urea (CRU) and regular urea (RU) for processing tomato and sunflower production.

Nitrogen fertilizer application increased processing tomato yield by 50 to 95 t/ha (71% to 137％) over the zero N control treatment. At the recommended N rate, application of 60% as basal CRU plus 40% as RU split, between flowering and fruiting, produced the highest fruit yield. This option performed better than a 100% basal application of RU alone, 100% basal CRU, or 70％ as basal CRU plus 30% of RU at flowering. At the 80% recommended N application rate, there was no significant difference in fruit yield between treatments either applied as RU and CRU alone, or in combinations. However, fruit yield of all the treatments was significantly lower than the full N recommendation supplied as 60% basal CRU plus 40% RU equally split between flowering and fruiting. The agronomic efficiency (AE-N) from CRU or CRU+RU was 74 to 157 kg/kg N higher and the recovery efficiency (RE-N) was 15 to 22% higher than RU alone. Also, the RE-N at 80% recommended N was 13 to 20% higher than 100% N recommendation. From an economic and environmental aspect, the best management practice for N was 60% basally applied as CRU, with the remaining 40% as RU - equally split between flowering and fruiting using 100% of the current N recommendation.

Nitrogen fertilization increased the seed yield of edible sunflower by 480 to 1,170 kg/ha (19.7% to 48.5%) over the zero N control treatment. At the recommended N application rate, basal application of RU alone produced a similar seed yield to basal application of CRU alone, but was significantly lower than basal application of CRU+RU, or a split application of RU. At 80% of the recommended N rate, there were no significant treatment differences in seed yield between basal application of CRU alone, CRU combinations with RU, or basal application of RU. However, yields at the 80% N recommendation were lower than basal application of CRU alone or in combinations with RU at the 100% N recommendation. The AE-N from basal CRU or CRU+RU was 1.2 to 2.9 kg/kg N higher and RE-N was 6 to 23% higher than basal application of RU alone. The RE-N at 80% of the N recommendation was 14 to 20% higher than the 100% N recommendation. From an economic and environmental aspect, the best management of N for edible sunflower was 40% basally applied CRU and 60% as RU using 80% of the current N recommendation.