Research Article: Irrigation has more influence than fertilization on leaching water quality and the potential environmental risk in excessively fertilized vegetable soils

Date Published: September 27, 2018

Publisher: Public Library of Science

Author(s): Yang Li, Juanqi Li, Lihong Gao, Yongqiang Tian, Wen-Xiong Lin.

http://doi.org/10.1371/journal.pone.0204570

Abstract

Excessive fertilization is a common agricultural practice that often negatively influence soil and environmental quality in intensive vegetable production systems in China. To reduce negative effects of excessive fertilization, current studies generally focused on fertilizer management but not irrigation. In this study, we investigated the effects of fertilization and irrigation on soil properties, leaching water characteristics, plant growth, cucumber yield, irrigation water use efficiency (IWUE) and partial factor productivity of nitrogen (PFPN) in a double cropping system. The treatments included (i) conventional irrigation with conventional N fertilization (IcNc), (ii) optimal irrigation with conventional N fertilization (IoNc), (iii) conventional irrigation with optimal N fertilization (IcNo), and (iv) optimal irrigation with optimal N fertilization (IoNo). In general, fertilization merely influenced concentrations of nitrate (NO3-), phosphorus (P) and potassium (K), but did not affect most leaching water characteristics. In contrast, irrigation influenced pH, EC and concentrations of P, K, Ca, Mg, Na and Cu. Cumulative leached amounts of NO3-, P, K, Ca, Mg, Na, Fe, Cu and Zn were significantly decreased by optimal irrigation as compared to conventional irrigation under same fertilization conditions, but not by optimal fertilization as compared to conventional fertilization under same irrigation conditions. The leachate volume was strongly positively correlated with cumulative leached amounts of all tested elements, and these relationships were obviously influenced by irrigation but not fertilization. The IoNo treatment significantly increased both IWUE and PFPN as compared to the IcNc treatment. However, the IcNo treatment only enhanced PFPN, while the IoNc treatment improved IWUE, when compared to the IcNc treatment. Our results suggested that irrigation has more influence than fertilization on leaching water quality and that the optimal irrigation combined with optimal fertilization was efficient in reducing the potential environmental risk caused by excessive fertilization in intensive vegetable production systems.

Partial Text

China’s population accounts for approximately 19% of the world’s population. However, China’s arable land accounts for only about 7% of the cultivated land in the world. To produce adequate food, since the early 1980s, Chinese agriculture has intensified greatly on a limited land area with large inputs of fertilizers, and has finally obtained relatively high crop yields on limited land [1]. Solar greenhouse is a common vegetable cultivation facility in China. Since solar greenhouse uses solar energy as the sole source of light and heat for vegetable production, it has developed rapidly in China [2], encompassing 4.0 million ha in 2015 [3]. Unfortunately, to obtain high crop yields, Chinese farmers often apply excessive fertilizers and irrigation water during crop production. For instance, in some greenhouse vegetable cultivation regions in China, annual irrigation rate was as high as 1000 mm, and fertilizer N apparent recovery efficiency was only 18–33% of applied N taken up by the vegetables. [4]. Consequently, redundant water and fertilizers can cause serious environmental problems, such as greenhouse gas emission, soil degradation, freshwater contamination, and natural resource consumption [5,6].

Excessively fertilized vegetable soils generally had high nutrient leaching. Optimal irrigation was more efficient than optimal fertilization in reducing nutrient leaching in excessively fertilized soils. In addition, irrigation had more influence than fertilization on leaching water quality in excessively fertilized soils. In general, fertilization merely influenced concentrations of nitrate (NO3-), phosphorus (P) and potassium (K), but did not affect most leaching water characteristics. In contrast, irrigation influenced pH, EC and concentrations of P, K, Ca, Mg, Na and Cu. Cumulative leached amounts of NO3-, P, K, Ca, Mg, Na, Fe, Cu and Zn were significantly decreased by optimal irrigation as compared to conventional irrigation under same fertilization conditions, but not by optimal fertilization as compared to conventional fertilization under same irrigation conditions.

 

Source:

http://doi.org/10.1371/journal.pone.0204570

 

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