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Title: Impact of cultivation year, nitrogen fertilization rate and irrigation water quality on soil salinity and soil nitrogen in saline-sodic paddy fields in 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
item YANG, HAOYU - Chinese Academy Of Sciences
item LIU, MIAO - Chinese Academy Of Sciences

Submitted to: Journal of Agricultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/19/2015
Publication Date: 8/12/2015
Citation: Huang, L., Liang, Z., Suarez, D.L., Wang, Z., Wang, M., Yang, H., Liu, M. 2015. Impact of cultivation year, nitrogen fertilization rate and irrigation water quality on soil salinity and soil nitrogen in saline-sodic paddy fields in Northeast China. Journal of Agricultural Science. doi: 10.1017/S002185961500057X.

Interpretive Summary: Saline sodic soils are generally either not utilized for irrigated crop production, or else abandoned as unsuitable for such use, due to the elevated salinity, poor soil structure and low water infiltration. Nonetheless these soils can potentially be reclaimed for use with irrigated crops, resulting in a vast increase in land productivity. Paddy rice production has been considered suitable for the initial stages of reclamation as subsurface drainage is not required or desired with this crop. In this study we examine the potential for crop production and reclamation of saline sodic soils with elevated pH in the western Songnen Plain in Northeast China, soils especially challenging to utilize as they are also severely depleted in N and elevated pH has an adverse impact on plant growth. We followed the impact of irrigation on soil chemical properties for 1, 3, 6 and 9 years following the initiation of rice production. Experimental treatments included application of 0, 100, 200 and 300 kg of N per year using either river or ground water, in addition to initial application of P and K fertilizer. Soil N levels increased with time but there was little change in soil EC, pH or sodicity. The soils were reclaimed for rice production but the soils are still saline and sodic so their use for other crops is still very limited. Reclamation in the sense of reduction in salinity, pH and sodicity did not occur due to the extremely low infiltration rates. Large quantities of Ca and acid amendments would be required to lower the soil pH and sodicity and improve infiltration, thus these high clay soils appear suitable only for rice production. This information is of use to growers and extension personnel worldwide interested in options for utilization and reclamation of saline sodic soils for crop production.

Technical Abstract: Saline-sodic soils are a valuable potential arable land resource, and are widely distributed in the western Songnen Plain of Northeast China. Reclaiming and planting rice is an effective and feasible approach for improving saline-sodic soil and increasing food production. Assessment of the effectiveness and sustainability of this method requires monitoring of the changes in soil salinity and nutrient content. The objective of this study was to investigate the changes of soil salinity and nitrogen contents over up to nine years of cultivation, different nitrogen application rates and different irrigation water types. In total, we examined fields after 1, 3, 6, and 9 years of cultivation, four nitrogen application rates (N0: no nitrogen, N1: 100 kg N/ha, N2: 200 kg N/ha and N3: 300 kg N/ha) and two irrigation water types: ground water irrigation (GWT) and river water irrigation (RWI). We analyzed soil and water samples before and after throughout the experiment. We found that soil pH and EC, especially those in the surface layer of 0-40 cm depth, decreased with years of cultivation whether with GWI or with RWI, while soil inorganic nitrogen and total nitrogen contents were increased. Moreover, with increasing nitrogen application levels, soil inorganic nitrogen and total nitrogen contents increased significantly in the 0-20 cm soil layer. Increasing N application had little effect on soil pH and EC. Reclaiming and planting rice promoted the desalination of the surface and fertile tillage layer in saline-sodic paddy fields. In terms of irrigation and drainage in saline-sodic paddy field, both soil salinity and nitrogen contents were increased, soil total salinity annually increased 34 kg/ha and 12.8 kg/ha, and inorganic nitrogen contents annually increased 9 kg/ha and 13.5 kg/ha with GWI or RWI, respectively. Therefore, some comprehensive agricultural practices should be done for improving and cropping rice in saline-sodic paddy field, such as soil improvement, fertilization and so on.