Agronomic evaluation of control-release urea (CRU) in maize and rice in Heilongjiang

The objective of this project, initiated in 2015, was to study how regular urea (RU) can be substituted with controlled-release urea (CRU) to improve yield and N use efficiency of maize and rice in Heiongjiang Province. Treatments were designed to compare farmer’s practice (FP), soil test-based fertilization (OPTS), and combinations of NPK that substituted CRU for RU at various proportions and rates. Timing of N application was also studied using various splits between planting and in-crop (stalk elongation stage). IPNI's Nutrient Expert® Maize (NE) was used to prescribe N application in selected treatments. Maize was grown in the town of Minzhu near Harbin City, Heilongjiang. Rice was grown in Qingan County, Heilongjiang.

In maize, grain yield was not affected by the substitution of RU with CRU, and yields did not differ from the FP or OPTS, when the full N recommendation was used. Treatments designed to provide 20% less N had lower grain yields regardless of the source. Full N rate treatment combinations with 60 to 75% of the N supplied as CRU effectively provided 17% to 7% less N to the maize crop, but still maintained the same yield as FP and OPTS treatments. The CRU treatments achieved higher agronomic (AE) and recovery efficiencies (RE) than the FP or OPTS.

In rice, the combination of providing the full rate of N using 75% CRU and 25% of RU generated higher grain yield and N efficiency parameters than those obtained under FP or OPTS.

Use of NE software hold promise as a decision support tool for determining the right source, rate, and timing recommendations for fertilizer application if traditional soil testing is not available.