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Sweet potato (Ipomoea batatas L.) is a promising food and industrial crop that plays an important role in China’s agricultural poverty relief strategy. Selecting an appropriate cropping system for sweet-potato production could simultaneously achieve energy, economic, and environmental benefits. Therefore, the comprehensive assessment of diversified sweet-potato-based cropping systems (i.e., sweet potato monoculture (SP), continuous sweet potato cropping (SPSP), sweet potato–rice (SPRI), sweet potato–maize (SPMA), and sweet potato–potato (SPPO)) in South China was conducted with a field survey and life-cycle assessment. The data were collected quantitatively using a questionnaire for face-to-face interviewing of 70 farmers. The results indicated that the annual crop yield (sweet potato equivalent yield) of five cropping systems was in increasing order as SPPO > SPSP > SPMA > SPRI > SP. The SPMA system exhibited the highest net energy (499.09 GJ/ha) and energy rate (7.77). The SPSP system performed better in energy efficiency (0.90 kg/MJ), net return (140,284 CNY/ha), benefit to cost rate (3.20), and eco-efficiency (45 CNY/kg CO2-eq). The annual greenhouse-gas (GHG) emissions of five cropping systems ranked from lowest to highest as follows: SP < SPRI < SPSP < SPMA < SPPO. With comprehensive consideration, extended rotation systems (e.g., SPMA, SPRI, and SPSP) are proposed because they could effectively reduce GHG emissions while maintaining or even increasing the system’s productivity (ensuring food safety) in South China.

Subsurface pipe drainage technology can effectively improve coastal saline land in Northern China. We explored an okra (Abelmoschus esculentus L.)-assisted subsurface pipe drainage system to improve the water and salt discharge performance and benefits. In this study, the simulation box experiment was conducted to research the response of water and salt discharge performance in subsurface pipe drainage to okra root weight density (RWD). The drain outflow, soil salinity, and sodium adsorption ratio were determined. The results showed that okra RWD affected the vertical distribution of okra roots. Okra with an appropriate RWD (about 116 μg·cm−3) could significantly increase the cumulative drain outflow. Okra with an appropriate RWD (about 136 μg·cm−3) could significantly increase the desalting effect. Moreover, the RWD of okra also influenced the ability of subsurface pipe drainage to inhibit soil alkalization. The above results show that planting okra and installing subsurface pipe drainage to control drainage at the coastal saline land in Northern China can effectively improve the water and salt drainage effect when okra RWD is about 116–136 μg·cm−3. When using subsurface pipe drainage to improve coastal saline soils, planting okra with proper density may be an appropriate choice to improve the effect and benefit.

Freshwater shortage and soil salinization are the major constraints for alfalfa (Medicago sativa L.) growth in coastal salt–alkali soil of North China. In this study, we analyzed the effects of shallow groundwater tables and alfalfa cultivars on forage yield and nutritional value. A field simulation experiment was conducted during the growing season of 2019–2021 with three groundwater depths (80, 100, and 120 cm) and five alfalfa cultivars (Magnum 551, Phabulous, Zhongmu No. 1, Zhongmu No. 3, and WL525HQ) under subsurface pipe systems. Alfalfa forage was harvested six times in total during the growing season. Results revealed significant variation among alfalfa cultivars for forage yield at each shallow groundwater depth. The greatest forage yield was recorded in cultivar Phabulous (32.2 and 35.9 t ha−1 in 2020 and 2021) when planted at 100 cm shallow groundwater depth. Forage yield during the first harvest was 24.6–25.7%, exhibiting the highest ratio of the total annual yield. The effects of shallow groundwater depth, cultivar, and their interaction were significant (p < 0.01) on the turn-green ratio of alfalfa. Cultivar Zhongmu No. 1 had the highest turn-green ratio at the 100 cm groundwater depth, while cultivar WL525HQ showed the lowest turn-green ratio at each groundwater depth. Moreover, crude protein (CP), neutral detergent fiber (NDF), and acid detergent fiber (ADF) content were also significantly affected by shallow groundwater depth, cultivars, and their interaction at different harvests. Cultivars Magnum551, Zhongmu No. 1, Zhongmu No. 3, and Phabulous furnished the highest CP, while cultivar WL525HQ performed the poorest in terms of CP in this study. These results propose that planting the cultivar Phabulous at a groundwater depth of 100 cm could be a suitable agronomic practice for alfalfa forage production in the coastal salt–alkali area of North China.

Alfalfa (Medicago sativa L.) production is affected by many factors, including management practices, soil conditions, and the environmental elements of the target area. Varietal differences, in terms of agronomic performance and forage yield, among 50 alfalfa cultivars under six harvest systems following regrowth were evaluated during the growing season of 2019–2020 under non-irrigated rainfed conditions in a coastal saline-alkali soil region of North China. Days to harvesting, plant height, canopy area, growth rate, and forage yield were assessed to rank the cultivars. Furthermore, the key factor influencing the regrowth of the second year after over-wintering was identified based on the growth status before over-wintering by using the Boston Matrix method. Results showed significant (p < 0.05) differences among cultivars and harvests regarding plant height, canopy area, and forage yield. Alfalfa forage yield ranged between 24.2 t ha−1 yr−1 and 32.7 t ha−1 yr−1. The highest forage yield was obtained in cultivar Guochan No.1, and was lowest in cultivar Magnum 601. Forage yield reached the greatest values for the first harvest, and then decreased gradually and changed stably. The forage yield of the third, fourth, fifth, and sixth harvest ranged from 3.4 t ha−1 to 4.3 t ha−1 (averaged across 50 cultivars), which represented 10.8% to 15.2% of the annual total forage production. We also observed that forage yield correlated strongly, but negatively, with the growth rate. According to subordinate function value analysis, Womu No.1, WL440HQ, Weston, Surprise, and WL354HQ proved optimum cultivars for general cultivation in this coastal area. In future, development of alfalfa cultivars with improved regrowth and tolerance to heavy saline-alkali soil and early spring drought would be necessary to increase forage yield under rainfed conditions in coastal saline-alkali areas of North China.