Effects of Nitrogen Conservation Measures on the Nitrogen Uptake by Cotton Plants and Nitrogen Residual in Soil Profile in Extremely Arid Areas of Xinjiang, China

Jinhu Zhi,Xinlu Bai,Mengjie Xia,Zhujun Chen,Jianbin Zhou,Taoyu Qiu

doi:10.3390/pr10020353

Jinhu Zhi, Xinlu Bai + Show 4 more

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https://doi.org/10.3390/pr10020353

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Abstract

This study researched the effects of using various nitrogen (N) conservation measures on the residual characteristics of nitrate and ammonium N in soil and the associated N uptake by cotton plants. A field experiment with six treatments was conducted, as follows, no N application (DT1), conventional N application (DT2), 60% conventional N application combined with DCD (DT3), 60% conventional N application combined with NBPT (DT4), 60% conventional N application combined with cotton straw returning (DT5), and 60% conventional N application combined with DCD, NBPT, and cotton straw returning (DT6). The results showed that the cotton straws in the DT5 treatment were beneficial for the vegetative growth of cotton seedlings. However, it was observed that the later performance of the plants in this sample was poor in terms of height, biomass, and yield of cotton. The plant height in the DT6 sample increased by 15 cm compared with those in DT1, and the soil and plant analyzer development (SPAD) values of the fourth leaf from the top of the DT6 plants were higher than those in the DT1 and DT4 samples. The DT6 plants (60% Urea + DCD + NBPT + cotton straw) increased N use efficiency by up to 47%, and no significant decrease in biomass and cotton yield was observed compared to the DT2 sample. The residual content of nitrate N in the tillage layer increased gradually over time between two rounds of drip irrigation treatment applications. Compared with the DT2 treatment, the other treatments resulted in lower residual nitrate N contents. In summary, the application of N fertilizers at a reduced rate combined with N conservation measures may increase N use efficiency and decrease the risk of non-point source N fertilizer pollution, while maintaining the cotton yield.

Highlights

With its wide-ranging applications, cotton is the world’s most vital economic crop [1].The Tarim Basin in China is an arid region with a high cotton yield and unique climatic and soil conditions
The difference in the height of the cotton plants between DT6 and DT4 was not significant after the budding stage, but the cotton plant height for these two treatments was significantly greater than that for the other treatments. This result indicates that the application of urea with a nitrification inhibitor alone (DT3) and the application of urea with cotton straws alone (DT5) were unfavorable for increasing the height of cotton plants
We proposed a concept of phase nitrogen use efficiency (PNUE), which is defined as the proportion of cumulative N uptake during the period from the application of N to the end of a given stage in relation to the total amount of N applied

Summary

Introduction

The Tarim Basin in China is an arid region with a high cotton yield and unique climatic and soil conditions. It is located in China’s main cotton planting region, Xinjiang, where cotton production accounts for 83% of the total national production [2,3,4]. Many factors affect cotton yield [5], among which nitrogen (N) is the main limiting factor for its growth. Urea is the most common N fertilizer used for cotton production in China. Within two to three weeks after urea application, the fertilizer is converted to a mobile nitrate (NO3 − N) through nitrification [6]. The volatilization of Nitrous oxide (N2 O) due to denitrification and the volatilization of ammonia (NH3 ) due to the presence of ammonium nitrogen (NH4 + ) results in the loss of most of the N fertilizer following its application to the soil

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