Effects of nitrogen type on rainfed maize nutrient uptake and grain yield

Urea blended with slow-release nitrogen fertilizer (UNS) is considered as a promising alternative to increase crop yields compared with the conventional split urea (U) application or slow-release nitrogen fertilizer (SRF). However, the yield-increasing effect and mechanism of UNS under different rainfall conditions is still unclear. A field experiment was conducted during 2016-2020 to evaluate the effects of UNS on dry matter (DM), nutrient uptake, and grain yield of rainfed maize (Zea mays L.) in Northwest China. The results showed that UNS increased the average total DM and N uptake by 19.6 and 27.5% compared with U, and by 15.8 and 18.2% relative to SRF, respectively. The average maximum DMaccumulation and N uptake rates in UNS were increased by 26.5 and 6.5% compared with those in U, and by 20.4 and 14.0% relative to those in SRF, respectively. Compared with U and SRF, UNS increased N remobilization from vegetative organs to grains after silking by 51.9 and 40.7%, respectively. Dry matter accumulation, NPK uptake, and N remobilization in 2017 ("pre-dry") and 2018 ("normal") were greater than those in 2016 ("post-dry"), 2019 ("wet"), and 2020 ("wet"). Grain yield in U was relatively low and stable over the five growing seasons, while grain yield followed the order of 2017 > 2018 approximate to 2019 approximate to 2020 > 2016 in UNS, and 2018 approximate to 2019 > 2020 > 2017 > 2016 in SRF. The UNS increased grain yield by 46.2 and 28.6% compared with U and SRF, respectively. Therefore, UNS can be used as a promising N management practice to improve the ability of agricultural ecosystems to cope with climate change, and ultimately maintain high crop yields.