Single fertilization of urea in root zone improving crop yield, nutrient uptake and use efficiency in summer maize

Abstract: Appropriate fertilization practices are critical for improving crop yields and increasing nitrogen use efficiency (NUE). Split surface broadcasting (SSB) of nitrogen is typically practiced for summer maize (Zea Mays L.) in China. However, the SSB of nitrogen is labor intensive and causes large amount of nitrogen leaching or runoff into the environment, yet it does not substantially increase maize yields. Deep placement of nitrogen fertilizers has been widely recognized as an efficient way to solve such problems. However, limited information is available on the effect of one-time deep placement of urea on plant growth, nitrogen uptake and NUE in maize cropping system. Therefore, the object of this study was to investigate the effect of nitrogen application method on maize yield and NUE, which could not only provide an optimum one-time fertilization for summer maize, but also decrease chemical nitrogen fertilizers input to reduce environmental risks and maintain the sustainable development of maize cropping system. A two-year consecutive field experiment was conducted from 2015 to 2016 in Taihe and Dongzhi counties of Anhui province to study the effect of different nitrogen application methods on crop yield, nutrient uptake and fertilizer use efficiency in maize cropping system. There were four treatments, CK (with no N fertilizer), two-split surface broadcasting (SSB), one-time root-zone fertilization (RZF, all nitrogen fertilizers were point deep-placed at one time as a basal fertilizer into a hole 5 cm away from the seed and 12 cm under the soil surface), and one-time band deep placement (BDP, the nitrogen fertilizers were applied in a band at 5 cm from the seed and 12 cm under the soil surface as basal fertilizer). The results showed that the grain yield of different application methods was as follows: RZF>SSB≈BDP> CK. RZF achieved the highest grain yield in all treatments, which was 8.8% and 9.8% significant higher than that of the SSB and BDP, respectively. Similarly, the uptake of N, P and K by plant in RZF was the highest in all treatments. The N apparent recovery efficiency (ARE) in RZF was 50.1% to 58.9%, which was increased by 8.3 and 12.4 percentage points compared with SSB and BDP, respectively. Moreover, both the N agronomy efficiency (AE) and N partial factor productivity (PFP) were highest in RZF in all treatments. The P apparent recovery efficiency in RZF was 17.5%, which was 2.7 (increased by 18.1%) and 3.7 (increased by 27.2%) percentage points higher than that in SSB and BDP, respectively. Under the same nitrogen application rate, crop yield, biomass and nitrogen uptake by plant in Taihe were 31.5%, 25.2% and 46.3% higher than that in Dongzhi. The increase of maize yield and nitrogen use efficiency for RZF was probably due to the decreased soil volume with which the N fertilizer was mixed and reduced nitrogen release rate, thus it had an effect on slowing fertilizer release and matching the requirement of nitrogen during the plant growth period. The present study showed that there was a great potential and space for increasing crop yield and fertilizer use efficiency by optimizing fertilization methods, and the one-time RZF can achieve high yield in crop, high efficiency in fertilization, which was worth developing and applying the special root-zone fertilization machinery. In conclusion, these findings help us better understand the nitrogen uptake and use efficiency of one-time fertilization in maize cropping system, and provide references and recommendations for nitrogen management in this study area.