Effects of microbial fertilizer and alternate micro-sprinkler irrigation with different water amounts on soil health, root rot incidence, and yield of P. notoginseng under under shaded cultivation

Abstract

Soil moisture, soil nutrients, soil enzyme activity, and soil microbial quantity played important roles in Panax notoginseng (Burk) F. H. Chen production but the interaction mechanisms between these indicators and yield and root rot incidence remained contradictory and inconclusive. The objective of this study was therefore to build interaction relationships between these soil indicators and yield and root rot incidence by analysing the effects of different irrigation schedules and microbial fertilizer application on these soil properties, yield, and root rot incidence. A two-year field experiment was conducted in the process of P. notoginseng cultivation under three micro-sprinkler irrigation schedules (J1: 5 mm, J2: 15 mm, J3: 5/15 mm, alternate irrigation) and microbial fertilizer application (F1: 0.24 t ha−1, F2: 0.33 t ha−1) in Yunnan Province of southwest China. The results indicated that three micro-sprinkler irrigation schedules and microbial fertilizer application significantly affected soil moisture, soil nutrients, soil enzyme activity, and soil microbial quantity in the root zone of P. notoginseng. The soil moisture was ranked from high to low as follows: J2 > J3 > J1 and F2 > F1 during the seedling, flowering, and fruiting stages in 2019 and 2020. Compared with treatments J1F2 and J2F2, the J3F2 treatment significantly increased the populations of actinomycetes and catalase activity, while decreasing soil nutrient content ((Formula presented.), AP, AK), fungus counts, bacterial counts, sucrase activity, and urease activity. The lowest root rot incidence (6.73% in 2019, 6.11% in 2020) and the largest yield (2735 kg ha−1 in 2019, 3208 kg ha−1 in 2020) was obtained in the J3F2 treatment. The interaction relationships between soil indicators and yield and root rot incidence were built by using Partial Least Squares Path Modelling (PLS-PM) in order to reveal the interaction mechanisms between these indicators and yield and root rot incidence. We found that soil moisture, (Formula presented.), soil actinomycete quantity, and soil catalase activity were the main control factors for decreasing root rot incidence and increasing yield in P. notoginseng root zone soil. Moreover, the economic benefits (19.07 × 104 $ ha−1 in 2019, 27.94 × 104 $ ha−1 in 2020) were in J3F2 treatment higher than that in other treatments. Therefore, this study recommended alternate irrigation (J3, 5/15 mm) and microbial fertilizer application (F2, 0.33 t ha−1) might be an adaptive water-fertilizer management strategy for decreasing root rot incidence, increasing yield, and economic benefits.