Biochar addition combined with daily fertigation improves overall soil quality and enhances water-fertilizer productivity of cucumber in alkaline soils of a semi-arid region

Abstract

Crop land degradation is a common phenomenon in most regions of the world, especially in arid and semi-arid regions. To mitigate cropland degradation and further enhance crop productivity, it is crucial to restore soil quality by utilizing efficient soil management practices. Although biochar has been widely used to improve soil conditions, the efficiency of biochar in enhancing crop productivity is often limited by inappropriate agricultural practices (e.g. irrigation and fertilization). Moreover, little information is available regarding the link among availability of water, biochar and productivity. In this study, we measured the effects of biochar addition, daily fertigation and their combination on overall soil quality, crop yield and water-fertilizer productivity in alkaline soils of a semi-arid region, over two years. To comprehensively evaluate soil quality, a wide range of soil physical, chemical, biological and ecological properties were measured and integrated into a soil quality index (SQI). The treatments evaluated were (i) untreated soils managed with traditional irrigation and fertilization (control), (ii) soils treated with biochar and managed with traditional irrigation and fertilization (B), (iii) untreated soils managed with daily fertigation (DF), and (iv) soils treated with biochar and managed with daily fertigation (B + DF). In general, biochar addition enhanced soil quality (expressed by SQI) mainly through increasing soil water content (SWC), available phosphorus (AP), the capacity of soil microbes to utilize miscellaneous (CSM-MI) and microbial biomass carbon (Cmic), and decreasing soil pH and plant-parasitic nematode abundance. Daily fertigation improved soil quality primarily by enhancing SWC, AP, CSM-MI and Cmic. The SQI exhibited strong positive correlations with both plant biomass and fruit yield. In addition, the treatment B + DF showed not only the highest SQI and fruit yield, but also the highest irrigation water-productivity (326.3 and 557.9 kg mm−1 in 2017 and 2018, respectively) and partial factor productivity for fertilizer in both years 2017 and 2018. Our results show that biochar addition combined with daily fertigation can improve overall soil quality, and further enhance cucumber yield and water-fertilizer productivity in alkaline soils.