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Title: Effects of continuous nitrogen application on seed yield, yield components and nitrogen-use efficiency of Leymus chinensis in two different saline-sodic soils of Northeast China

Author
item HUANG, LIHUA - Chinese Academy Of Sciences
item LIANG, ZHENGWEI - Chinese Academy Of Sciences
item Suarez, Donald
item WANG, ZHICHUN - Chinese Academy Of Sciences
item WANG, MINGMING - Chinese Academy Of Sciences

Submitted to: Crop and Pasture Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/25/2019
Publication Date: 4/30/2019
Citation: Huang, L., Liang, Z., Suarez, D.L., Wang, Z., Wang, M. 2019. Effects of continuous nitrogen application on seed yield, yield components and nitrogen-use efficiency of Leymus chinensis in two different saline-sodic soils of Northeast China. Crop and Pasture Science. 70(4):373-383. https://doi.org/10.1071/CP18274.
DOI: https://doi.org/10.1071/CP18274

Interpretive Summary: The grasslands of the western Songnen Plain of Northeast China are mostly classified as saline or saline sodic and are currently low in productivity. As these lands are N deficient, they respond positively to N application. To further clarify the impact of nitrogen application on Leymus chinensis, seed yield and related parameters were monitored in a field experiment with two saline-sodic soils at the Da'an Sodic Land Experiment Station (DASLES) from 2010 to 2011. One field was classified as moderate saline–sodic grassland (MSSL) and the other severe saline–sodic grassland (SSSL). Nitrogen application rates were 0 (no fertilizer as control), 30, 60, 90, 120, 150, 180, and 210 kg N ha–1. Nitrogen application significantly improved seed yield mainly through increased spike number and heading percentage of Leymus chinensis. The seed yield of Leymus chinensis was increased 7.4 to 10.9 times with nitrogen application rate of 150 kg ha-1 as compared to no nitrogen application in MSSL, and 5.3 to 7.5 times with nitrogen application rate of 120 kg ha-1 as compared to those with no nitrogen application in SSSL. There are some significant differences in seed yield between 2010 and 2011 and between MSSL and SSSL under the same nitrogen addition rates. Nitrogen application also significantly impacted various nitrogen efficiencies of Leymus chinensis in the two saline-sodic soils. Correlation analysis demonstrated that seed yield and nitrogen efficiencies are not the best parameters to determine the optimum nitrogen application. Nitrogen application was a most practical and effective method to increase seed yield of Leymus chinensis in moderate saline-sodic grasslands, but not in severe saline sodic grassland where the limiting factor appeared to be elevated pH. This information is of direct use to land management specialists attempting to increase grassland productivity while minimizing cost and adverse environmental impacts of excess N application.

Technical Abstract: The effect of nitrogen (N) application on seed yields and yield components in Leymus chinensis (Trin.) Tzvel., a perennial rhizomatous grass, was measured in a field experiment with two saline-sodic soils at Da’an Sodic Land Experiment Station during 2010–11. Two grassland field sites were classified as moderately saline–sodic (MSSL) and severely saline–sodic (SSSL). Application rates of N at each site were 0, 30, 60, 90, 120, 150, 180 and 210 kg ha–1. Application of N significantly improved seed yield mainly through increased spike number (R2 = 0.96, P = 0.001). Compared with nil N, seed yield increased 7.4–10.9 times with N application of 150 kg ha–1 at MSSL, and 5.3–7.5 times with N application of 120 kg ha–1 at SSSL. However, absolute increases at SSSL were relatively small. Some significant differences (P = 0.01) in seed yield occurred between 2010 and 2011 with different N application rates in the same soil, and between MSSL and SSSL in the same year. Increasing N application rate significantly decreased N physiological efficiency (NPE) but increased N apparent-recovery fraction (NRF) and N partial-factor productivity (NPP) at both sites. Seed yield and NPP indicated that the optimal N application rates to increase yield were 150 kg ha–1 at MSSL and 120 kg ha–1 at SSSL. High soil pH was the major factor adversely impacting seed yield, and pH and soil salinity were major factors negative affecting NPE, NRF and NPP as well as decreasing the positive effect of N application. Nitrogen application is a practical and effective method to increase seed yield of L. chinensis in saline-sodic grasslands of Northeast China, particularly when soil pH and salinity are not limiting.