The application of sanitary sewage using subsurface drip irrigation contributes to mitigating the current problems of water availability and food production. The aim in this study was to evaluate cowpea receiving sanitary sewage through drippers operating at different flow rates and depths. The drippers operated at flow rates of 1.6 and 3.8 L h(-1) and were installed at depths of 0, 5, 10, 15, 20, 25, and 30 cm. Cowpea was grown in 65 L pots filled with sandy clay soil in a greenhouse. Synthetic sanitary sewage was used and the amount applied to the pots was based on the limiting element, which in this case was nitrogen, for growing cowpea. Irrigation was managed using TDR probes. Germination and the physiological responses and morphology of cowpea roots were assessed. Capillary rise, when water was applied in subsurface, was not sufficient to evenly moisten the soil surface. The germination variables decreased as a result of the increase in drip installation depths. The distribution of water as the depth of the emitters increased was responsible for the damage to the physiological and morphological responses of cowpea roots. The flow rates of the drippers did not affect the germination of cowpea. Using the subsurface drip irrigation system was not appropriate for growing cowpea under the conditions of this study.

Capillary rise of water leads to salt migration and accumulation, which is the main cause of erosion at the bottom of the Great Wall in Northwest China. In this study, we evaluated the effectiveness of SH (modified polyvinyl alcohol) and lime composite material against capillary water rise. We conducted comparative capillary rise cycle tests on two sample types: untreated Great Wall soil and soil treated with the SH-lime composite, using solutions of NaCl and Na2SO4 of specified concentrations. The surface hardness, strength, water-salt distribution, and pore size distribution of the samples were also evaluated. The results showed that: in the salt solution capillary rise cycle, the untreated soil samples quickly changed color and precipitated white crystals. As the test proceeded, the untreated soil samples developed cracks, followed by fragmentation at the corners, and finally collapsed. In contrast, the SH-lime solidified soil had less white crystal precipitation and no visible cracks after 7 cycles. This indicates that the overall integrity of the SH-lime solidified soil was higher. The capillary rise cycles also changed the pore size distribution of the samples. NaCl crystals tended to occupy and expand micropores and small pores, while Na2SO4 crystals tended to grow in large pores. In addition, Na2SO4 was more destructive to soil than NaCl. The SH-lime composite material reduced porosity and strengthened soil structure, which slowed down the expansion of large pores. The study concludes that SH-lime effectively inhibits capillary rise-induced water-salt migration and associated damage, making it a suitable choice for repairing capillary rise-prone Great Wall sites.