Influence of inorganic and organic fertilizers on the performance of water-absorbing polymer amended soils from the perspective of sustainable water use efficiency

The frequent occurrence of unprecedented droughts has necessitated strategies for enhancing water use efficiency to boost agricultural production. Water-absorbing polymer (WAP) has emerged as a viable option for water stress management. However, the sensitivity of these hydrophilic WAP’s to the external ionic medium significantly affects their water absorption capacity. Therefore, the combined or hybrid use of WAP and organic/ inorganic fertilizers may inhibit the functionality of WAP, which needs to be thoroughly investigated. The objective of this study is to assess the performance of two different WAPs (a commercially available WAP and a laboratory synthesized WAP) with varying combinations of organic/ inorganic fertilizers in two different soil textures. The combined influence of fertilizers and WAP (a total of 13 combinations of treatment) on the soil-water retention curve (SWRC) of two agricultural soils (silt and silt loam) were quantified. The water-absorbing capacity (WAC) of both WAPs (Com-WAP and FA-WAP) was reduced under the influence of different fertilizers in the order of urea < organic < DAP. Despite the reduction in overall WAC, the combined use of fertilizers and WAP have improved the water retention in both the soils due to modification of the soil pore volume. The improvement in water retention was more significant in silt soil than the silt loam for both the WAPs. The sensitivity of FA-WAP to fertilizers was found to be less than Com-WAP. This opens up the possibility of engineering the WAP for better water use efficiency. Quantification from SWRC revealed a significant increase in plant wilting time and plant available water content (PAWC) under the combined influence of WAP and fertilizers. The study indicates the potential of WAP as an efficient soil conditioner even in the presence of fertilizer for countering the negative impacts of water stress conditions.