Nitrogen Fertilizer Deep Placement for Increased Grain Yield and Nitrogen Recovery Efficiency in Rice Grown in Subtropical China.

Meng Wu,Chunyu Jiang,Jia Liu,Zhongpei Li,Ming Liu,Weitao Li,Guilong Li

doi:10.3389/fpls.2017.01227

Abstract

Field plot experiments were conducted over 3 years (from April 2014 to November 2016) in a double-rice (Oryza sativa L.) cropping system in subtropical China to evaluate the effects of N fertilizer placement on grain yield and N recovery efficiency (NRE). Different N application methods included: no N application (CK); N broadcast application (NBP); N and NPK deep placement (NDP and NPKDP, respectively). Results showed that grain yield and apparent NRE significantly increased for NDP and NPKDP as compared to NBP. The main reason was that N deep placement (NDP) increased the number of productive panicle per m-2. To further evaluate the increase, a pot experiment was conducted to understand the N supply in different soil layers in NDP during the whole rice growing stage and a 15N tracing technique was used in a field experiment to investigate the fate of urea-15N in the rice–soil system during rice growth and at maturity. The pot experiment indicated that NDP could maintain a higher N supply in deep soil layers than N broadcast for 52 days during rice growth. The 15N tracing study showed that NDP could maintain much higher fertilizer N in the 5–20 cm soil layer during rice growth and could induce plant to absorb more N from fertilizer and soil than NBP, which led to higher NRE. One important finding was that NDP and NPKDP significantly increased fertilizer NRE but did not lead to N declined in soil compared to NBP. Compared to NPK, NPKDP induced rice plants to absorb more fertilizer N rather than soil N.

Highlights

To obtain high yields of cereal crops, high rates of N fertilizer are applied in China (Liang et al, 2013)
A 3-year, consecutive field plot experiment indicated that N deep placement (NDP) increased early and late rice yield and N recovery efficiency (NRE) significantly compared to the N broadcast application (NBP) method in subtropical China
The stepwise regression analysis showed that PPN explained most of the variation of grain yield, which further determined the difference of NRE between different treatments

Summary

Introduction

To obtain high yields of cereal crops, high rates of N fertilizer are applied in China (Liang et al, 2013). The main topics of these studies have been: (1) determining that N fertilizer deep placement could reduce ammonia volatilization compared to broadcast application of N fertilizer (Rochette et al, 2013) and increase NRE (Huda et al, 2016); (2) seeking appropriate N application materials such as urea supergranules and briquette N (Mohanty et al, 1999; Gaudin and D’Onofrio, 2015) for N fertilizer deep placement; (3) identifying other specific agronomic practices for N fertilizer deep placement such as optimizing the depth of N fertilizer placement in different countries (Mohanty et al, 1999; Gaudin, 2012); (4) and developing and applying fertilization machines for deep fertilizing (Bautista et al, 2001; Liu et al, 2015) Few of these studies focus on the N distribution during rice growth under N fertilizer deep placement.

Methods

Results

Discussion

Conclusion