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Title: Continuous nitrogen application differentially affects growth, yield,and nitrogen use efficiency of Leymus chinensis in two saline–sodic soils of Northeastern 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 MA, HONGYUAN - Chinese Academy Of Sciences
item YANG, HAOYU - Chinese Academy Of Sciences
item LIU, MIAO - Chinese Academy Of Sciences

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/23/2015
Publication Date: 1/13/2015
Citation: Huang, L., Liang, Z., Suarez, D.L., Wang, Z., Ma, H., Yang, H., Liu, M. 2015. Continuous nitrogen application differentially affects growth, yield,and nitrogen use efficiency of Leymus chinensis in two saline–sodic soils of Northeastern China. Crop Science. doi: 10.2134/agronj14.0250.

Interpretive Summary: Degradation of grazing lands is a serious and increasing problem in arid and semi-arid regions of the world. Salinization of grazing lands is increasing in many of these regions compounding the adverse impacts of overgrazing. Leymus chinesis is a highly desirable grass species in northeastern China with tolerance to saline and sodic conditions. We evaluated the nitrogen requirements of Leymus chinesis and nitrogen use efficiency in a field study on degraded nitrogen- depleted, saline-sodic lands in the western Songnen plain of northeastern China. We examined nitrogen response under both high sodic (exchangeable sodium percentage of 38% and pH of 8.9) and severe sodic conditions (exchangeable sodium percentage of 50% and soil pH of 9.8) for three years. The nitrogen treatments considered of annual application of 0, 30. 60, 90, 120, 150, 180 and 210 kg nitrogen/ha. Application of 180 kg nitrogen/ha increased hay yield from 2 t/ha to 10.7 t in the high sodicity field and from 1 t/ha to 4.9 t/ha under in the field with severe sodicity conditions. Based on the experimental results including the nitrogen use efficiency of the treatments, optimal nitrogen application for three year restoration of the grasslands was 90 to 120 kg/ha under high sodicity conditions and 120-150 kg/ha under severe sodicity conditions. Nitrogen application is a viable option for restoration of degraded saline sodic grasslands under high pH conditions. This information is of interest to rangeland management specialists and extension specialists in arid and semi-arid regions of the world.

Technical Abstract: Leymus chinensis (Trin.) Tzvel. (Poaceae) is a dominant plant in the Western Songnen plain of Northeastern China, Soil salinization and alkalization, nitrogen deficiency and current management practices have resulted in grassland degradation in the region. The objective of this study was to investigate the effect of nitrogen addition on hay yield and nitrogen use efficiency of Leymus chinensis and the optimum nitrogen application rate in relation to soil saline-sodic conditions. To achieve this goal, we conducted a 3-year field experiment in two nearby fields at the Da'an sodic land experiment station of China from 2009 to 2011. The initial soil nitrogen condition was similar for both fields but the soil saline-alkaline level was moderate (ESP=37.9%, pH=8.9) in one field, (designated as MSAL), and severe (ESP=50.3%, pH= 9.8) in the other field (designated as SSAL). Accordingly, the fields were assigned as MSAL (moderate saline-alkaline grassland) and SSAL (severe saline-alkaline grassland). Nitrogen addition rates were 0 (no added fertilizer as control), 30, 60, 90, 120, 150, 180 and 210 kg N/ha. We determined that nitrogen addition could significantly improve plant height, population density, LAI (leaf area index) and hay yield of Leymus chinensis either in MSAL or in SSAL. There are some significant differences (P=0.05) in plant height, population density and LAI (leaf area index) during three years under the same nitrogen addition rate and in the same field, but no significant difference in Leymus chinensis yield (P>0.05) at the same nitrogen addition rate in the same field among the three years. Nitrogen addition can improve hay yield of Leymus chinensis from 2.0 t/ha with no nitrogen addition to more than 10.7 t/ha with a nitrogen application rate of 180 kg N/ha in MSAL, and from 1.0 t/ha with no nitrogen addition to 4.9 t/ha with nitrogen addition rate was 180 kg N/ha in SSAL. Hay yields of Leymus chinensis were increased 5.35 and 4.9 times when nitrogen addition rate was 180 kg N/ha in MSAL and SSAL respectively, when compared to the no nitrogen addition (control) treatment. Nitrogen use efficiencies were generally higher in MSAL than those in SSAL, the highest values of average NUE were the treatments with nitrogen addition rates with 120 kg N/ha in MSAL and 180 kg N/ha in SSAL. Based on comprehensive analysis of Leymus chinensis yield and nitrogen use efficiency data, our overall results support the use of nitrogen applications of 90 to 120 kg N/ha in MSAL and 120 to 150 kg N/ha in SSAL. Nitrogen addition can not only improve hay yield of Leymus chinensis, but also contain further grassland degradation in the Western Songnen Plain of northeastern China.