This study was conducted to explore the changes in soil microbial populations, enzyme activity, and tuber yield under the rotation sequences of Potato–Common vetch (P–C), Potato–Black medic (P–B) and Potato–Longdong alfalfa (P–L) in a semi–arid area of China. The study also determined the effects of continuous potato cropping (without legumes) on the above mentioned soil properties and yield. The number of bacteria increased significantly (p < 0.05) under P–B rotation by 78%, 85% and 83% in the 2, 4 and 7–year continuous cropping soils, respectively compared to P–C rotation. The highest fungi/bacteria ratio was found in P–C (0.218), followed by P–L (0.184) and then P–B (0.137) rotation over the different cropping years. In the continuous potato cropping soils, the greatest fungi/bacteria ratio was recorded in the 4–year (0.4067) and 7–year (0.4238) cropping soils and these were significantly higher than 1–year (0.3041), 2–year (0.2545) and 3–year (0.3030) cropping soils. Generally, actinomycetes numbers followed the trend P–L>P–C>P–B. The P–L rotation increased aerobic azotobacters in 2–year (by 26% and 18%) and 4–year (40% and 21%) continuous cropping soils compared to P–C and P–B rotation, respectively. Generally, the highest urease and alkaline phosphate activity, respectively, were observed in P–C (55.77 mg g^–1) and (27.71 mg g^–1), followed by P–B (50.72 mg mg^–1) and (25.64 mg g^–1) and then P–L (41.61 mg g^–1) and (23.26 mg g^–1) rotation. Soil urease, alkaline phosphatase and hydrogen peroxidase activities decreased with increasing years of continuous potato cropping. On average, the P–B rotation significantly increased (p <0.05) tuber yield by 19% and 18%, compared to P–C and P–L rotation respectively. P–L rotation also increased potato tuber yield compared to P–C, but the effect was lesser relative to P–B rotation. These results suggest that adopting potato–legume rotation system has the potential to improve soil biology environment, alleviate continuous cropping obstacle and increase potato tuber yield in semi–arid region.

Knowledge about fungi diversity following different planting patterns could improve our understanding of soil processes and thus help us to develop sustainable management strategies. The objective of this study was to determine the impact of different furrow-ridge mulching techniques on fungal diversity in rhizosphere soil under continuous cropping system. The investigated treatments were: flat plot without mulch (CK); flat plot with mulch (T1); on-ridge planting with full mulch (T2); on-furrow planting with full mulch (T3); on-ridge planting with half mulch (T4); and on-furrow planting with half mulch (T5). NGS (Illumina) methods and ITS1 sequences were used in monitoring fungi diversity of the potato rhizosphere soil. The fungi diversity in the rhizosphere soil was ranked in the order T5>T2>T4>T1>CK at the early growth stage and T2>T3>T1>T4>CK at the late growth stage of potato. The fungal communities found in the rhizosphere soil were Ascomycota, Zygomycota, Basidiomycota, Chytridiomycota and other unidentified fungal communities. Among the fungal community in the rhizosphere soil, Ascomycota was found to be dominant fungi population, with the highest percentage (89%) in the T5 soil whereas the T2 soils had the lowest percentage (67%). The Fusarium abundance in fully mulched treated soils was higher than in half mulched treated soil. The dominant genus in the T4 soil was Mortierella, whereas lower populations (1-2%) of Scutellinia, Cryphonectria, Acremonium and Alternaria were found in that treatment. Among the eumycetes, the dominant fungal class in all treated soils was the Sordariomycetes, which ranged from 57% to 85% in T2 and T5 soils, respectively. The Fusarium percentages in half mulched treated soils (T4, T5) were 55% and 28% lower than that of complete mulched treated soils (T2, T3), respectively. The cluster analysis results showed that, CK, T4 and T5 treated soils and T1, T2 and T3 treated soils had similarities in microbial compositions, respectively. Potato tuber yield was greater under the on-ridge planting with full mulch (T2) treated soil, followed by on-ridge planting with half mulch (T4) treated soil. The rhizosphere soil under the on-ridge planting with full mulch (T2) soil had the highest fungal diversity, suggesting that this management was the best environment

A field trial was conducted to determine the effect of nitrogen-enriched biochar on soil water content, plant’s photosynthetic parameters, and grain yield of spring wheat at the Dingxi Experimental Station during the 2014 and 2015 cropping seasons. Results showed that biochar applied with nitrogen fertilizer at a rate of 50 kg ha^–1 of N (BN₅₀) increased soil water content in the 0–30 cm depth range by approximately 40, 32, and 53% on average at anthesis, milking, and maturity, respectively, compared with zero-amendment (CN₀). Stomatal conductance and net photosynthetic rate after the BN₅₀ treatment increased by approximately 40 to 50% compared to CN₀. Soil water content and photosynthetic traits also increased in other treatments using straw plus nitrogen fertilizer, but to lesser extent than that of BN₅₀. Grain yields were highest (1905 and 2133 kg ha^–1 in 2014 and 2015, respectively) under BN₅₀. From this, biochar appears to have a potential for its use with N-fertilizer as a cost-effective amendment for crop production in semiarid environments.