Deficit irrigation and fertilization strategies to improve soil quality and alfalfa yield in arid and semi-arid areas of northern China.

Qianmin Jia,Muhammad Kamran,Lefeng Sun,Xiaolong Ren,Shahzad Ali,Peng Zhang,Zhikuan Jia

doi:10.7717/peerj.4410

Abstract

BackgroundIn the arid and semi-arid areas of northern China, overexploitation of fertilizers and extensive irrigation with brackish groundwater have led to soil degradation and large areas of farmland have been abandoned. In order to improve the soil quality of abandoned farmland and make reasonable use of brackish groundwater, we conducted field trials in 2013 and 2014.MethodsIn our study, we used three fertilization modes (CF, chemical fertilizer; OM, organic manure and chemical fertilizer; NF, no fertilizer) and three deficit irrigation levels (I0: 0 mm; I75: 75 mm; I150: 150 mm).ResultsThe results showed that the activities of soil urease, alkaline phosphatase, invertase, catalase, and dehydrogenase in the OM treatment were significantly improved compared with those in the CF and NF treatments under the three deficit irrigation levels. Compared with NF, the OM treatment significantly increased soil organic carbon (SOC), water-soluble carbon (WSC), total nitrogen, microbial biomass carbon and nitrogen (MBC and MBN), and soil respiration rate, and significantly decreased soil C:N and MBC:MBN ratios and the metabolic quotient, thus improving the soil quality of abandoned farmland. Furthermore, the OM treatment increased alfalfa plant height, leaf area index, leaf chlorophyll content, and biomass yield. Under the CF and OM fertilization modes, the activities of urease and catalase in I150 were significantly higher than those in I0, whereas irrigating without fertilizer did not significantly increase the activity of these two enzymes. Regardless of fertilization, alkaline phosphatase activity increased with an increase in irrigation amount, whereas invertase activity decreased.DiscussionThe results showed that deficit irrigation with brackish groundwater under the OM treatment can improve soil quality. Over the two years of the study, maximum SOC, total nitrogen, WSC, MBC, and MBN were observed under the OM-I150 treatment, and the alfalfa biomass yield of this treatment was also significantly higher than that of the OM-I0 treatment. Therefore, the OM-I150 treatment could be used as a suitable measure not only to improve the quality of abandoned farmland soil but also to increase the alfalfa biomass yield in arid and semi-arid areas of northern China.

Highlights

Exploitation and utilization of brackish groundwater has become a concern in many countries (Oster, 1994; Mondal, Bhuiyan & Franco, 2001; Jiang et al, 2012)
In order to improve soil quality in abandoned farmland and increase pasture production, we studied the effects of three fertilization modes and different deficit irrigation rates on soil enzyme activities, organic carbon, water-soluble carbon, total nitrogen, microbial biomass, respiration rate, and alfalfa yield
Our research indicated that brackish groundwater has a less inhibitory effect on soil enzyme activity due to the lower salt content (NaCl: 2.3 g L−1) in the water

Summary

Introduction

Exploitation and utilization of brackish groundwater has become a concern in many countries (Oster, 1994; Mondal, Bhuiyan & Franco, 2001; Jiang et al, 2012). Deficit irrigation has been widely used in agricultural production to improve crop yield and water-use efficiency (Shock et al, 2007; Du et al, 2010; Lindenmayer et al, 2011) It is not known whether using brackish water for deficit irrigation can improve soil quality and increase alfalfa production, and this needs further study. Compared with NF, the OM treatment significantly increased soil organic carbon (SOC), water-soluble carbon (WSC), total nitrogen, microbial biomass carbon and nitrogen (MBC and MBN), and soil respiration rate, and significantly decreased soil C:N and MBC:MBN ratios and the metabolic quotient, improving the soil quality of abandoned farmland. The OM-I150 treatment could be used as a suitable measure to improve the quality of abandoned farmland soil and to increase the alfalfa biomass yield in arid and semi-arid areas of northern China

Methods

Results

Discussion

Conclusion