Effect on Soil Properties and Crop Yields to Long-Term Application of Superabsorbent Polymer and Manure

Abstract

Intensive farming leads to soil degradation, and poses a serious threat to agricultural yield sustainability and soil ecology. Superabsorbent polymer (SAP) and organic manure (OM) are amendments that can remediate the soil, and improve soil structure and soil pore characteristics, thereby enhancing soil quality and promoting crop growth. These benefits may be enhanced through long-term continuous application of the amendments. X-ray computed tomography (CT) was used to determine the number, connectivity, and locations of pores (160–1,000 μm, >1,000 µm) in the soil at depths of 0–100 cm. Soil organic carbon content, proportion of water-stable macroaggregates (>0.25 mm) (WSM), soil bulk density, field water capacity, available water content, wilting point content, and saturated hydraulic conductivity were also determined. Compared to the control, long-term SAP and OM treatments significantly increased the number of 160–1,000 µm and >1,000 µm soil pores (5–20 cm depths), >1,000 µm and >160 µm soil porosity (at 0–20 cm depths), total organic carbon (10–20 cm and 40–50 cm), field water capacity (0–20 cm), available water content (0–20 cm), wilting point (10–30 cm), saturated water content (10–70 cm), saturated hydraulic conductivity (0–90 cm), and WSM (0–30 cm and 40–50 cm) while decreasing the soil bulk density (0–70 cm). Compared to OM, SAP had greater beneficial effects on the total organic carbon, soil field water capacity, available water content, saturated water content, saturated hydraulic conductivity, and WSM in soil at 0–20 cm depth. The improvements to soil quality resulted in an increase in the yields of wheat and maize. Therefore, although SAP and OM were both effective at improving soil properties and increasing the economic yield of wheat and maize, the effectiveness of SAP was greater than that of OM.

Effect of long term application of super absorbent polymer on soil structure, soil enzyme activity, photosynthetic characteristics, water and nitrogen use of winter wheat

“…SAP acts as a soil amendment, which can improve soil structure, soil pore characteristics ( Yang et al., 2011c ; Yang et al., 2018 ) and soil physical properties ( Yang et al., 2021 ; Yang et al., 2022 ), which in turn increases soil water retention and then facilitates microorganism growth. SAP could be strongly adsorbed to the soil particles, preventing dispersion of them ( Ajwa and Trout, 2006 ).…”

“…Under drought conditions, water has an important effect on the photosynthetic properties of wheat ( Keck and Boyer, 1974 ; Tezara et al., 1999 ; Lawlor and Cornic, 2010 ), and 90% to 95% of its yield comes from photosynthesis ( Li et al., 2006 ), especially in the late reproductive period, where photosynthates of functional leaves can contribute 80% to the grain ( Zheng, 1992 ). SAP have the function of improving soil structure ( Yang et al., 2021 ; Yang et al., 2022 ), reducing ineffective soil evaporation ( Yang et al., 2009a ), and storing water and moisture conservation ( Yang et al., 2012 ). In addition, SAP can regulate the physiological process and improve the photosynthetic efficiency of wheat ( Yang et al., 2009b ; Yang et al., 2011b ) by improving the soil water condition, regulating the relative water content or leaf water potential, and it is of great significance to reduce or slow down the damage degree of crops subject to drought stress.…”

“…This indicates that SAP can effectively improve the leaf photosynthetic rate while reducing the leaf transpiration, or be more beneficial for improving the Pn of wheat, and the Tr is also relatively higher, but, compared with CK, the Pn increased more significantly than Tr, thus leading to improved the LWUE. This indicates that the long-term application of SAP has a stable soil structure ( Yang et al., 2021 ; Yang et al., 2022 ) that regulates soil moisture, nutrients, and microbial enzyme activity ( Table 2 ) by buffering against the influence of drought stress ( Bodner et al., 2015 ), which is more beneficial in improving the photosynthetic efficiency per unit water utilization, and promoting dry matter accumulation ( Shi et al., 2016 ; Yang et al., 2021 ; Yang et al., 2022 ). Correlation analysis ( Table 5 ) showed that the increased photosynthetic rate promoted the improved wheat yield and nitrogen utilization efficiency.…”

“…Therefore, the application of SAP is an important measure in agricultural water conservation ( Niu et al., 2007 ), and also a hot topic in the study of dry farming area ( Huang et al., 1999 ). Studies show that the application of SAP could improve the root activity ( Yang et al., 2011a ) and physiological characteristics of wheat ( Yang et al., 2011b ), improve the water retention ( Khadem et al., 2010 ) and water supply capability of soil ( Song et al., 2009 ; Yang et al., 2012 ; Zhou et al., 2012 ), mitigate drought stress ( Hüttermann et al., 2009 ; Yun et al., 2017 ), regulate soil porosity ( Yang et al., 2011c ; Yang et al., 2018 ; Yang et al., 2022 ) and the structural characteristics of soil aggregates ( Wu et al., 2006 ; Yang et al., 2009a ; Yang et al., 2021 ), enhance soil microbial activity ( Dehkordi, 2018 ), stimulate the growth and development of crops ( Yang et al., 2011d ), and enhance photosynthesis ( Yang et al., 2009b ; Yang et al., 2011b ), so as to achieve higher crop yields ( Wu et al., 2007 ; Wu et al., 2010 ; Wu et al., 2011 ), precipitation and water use efficiency ( Yang et al., 2011d ; Lei et al., 2014 ), and nutrient utilization efficiency ( Lents, 1998 ). Li et al.…”

Long‐term combined subsoiling and straw mulching conserves water and improves agricultural soil properties

“…Subsoiling tillage can remediate subsoil compaction, break up the bottom of the plow and high‐density soil layer (Wang et al, 2014, 2020) while leaving the upper and lower soil layer intact (Singh et al, 2013), improve the water retention capacity and infiltration capacity of the soil (Kuang et al, 2020; Li & Hou, 2015), regulate the soil aggregate distribution (Baumhardt & Jones, 2005; Yang et al, 2021), promote root growth, and increase crop yield (Bennie & Botha, 1986; Yang, Duan, et al, 2022; Yang, Li, et al, 2022; Yang, Wu, et al, 2022). Cai et al (2014) and Wang and Li (2014) show that subsoiling tillage moderates soil temperatures and protects soil aggregate structures while increasing soil contents of moisture and organic carbon, while moderating soil temperature, thus providing favorable growth conditions that facilitate improved harvests.…”