Changes in Nutrient Accumulation and Transportation of Waxy Sorghum in Waxy Sorghum-Soybean Intercropping Systems Under Different Row Ratio Configurations

Effects of narrow-wide row planting patterns on canopy photosynthetic characteristics, bending resistance and yield of soybean in maize‒soybean intercropping systems

With the improvements in mechanization levels, it is difficult for the traditional intercropping planting patterns to meet the needs of mechanization. In the traditional maize‒soybean intercropping, maize has a shading effect on soybean, which leads to a decrease in soybean photosynthetic capacity and stem bend resistance, resulting in severe lodging, which greatly affects soybean yield. In this study, we investigated the effects of three intercropping ratios (four rows of maize and four rows of soybean; four rows of maize and six rows of soybean; six rows of maize and six rows of soybean) and two planting patterns (narrow-wide row planting pattern of 80-50 cm and uniform-ridges planting pattern of 65 cm) on soybean canopy photosynthesis, stem bending resistance, cellulose, hemicellulose, lignin and related enzyme activities. Compared with the uniform-ridge planting pattern, the narrow-wide row planting pattern significantly increased the LAI, PAR, light transmittance and compound yield by 6.06%, 2.49%, 5.68% and 5.95%, respectively. The stem bending resistance and cellulose, hemicellulose, lignin and PAL, TAL and CAD activities were also significantly increased. Compared with those under the uniform-ridge planting pattern, these values increased by 7.74%, 3.04%, 8.42%, 9.76%, 7.39%, 10.54% and 8.73% respectively. Under the three intercropping ratios, the stem bending resistance, cellulose, hemicellulose, lignin content and PAL, TAL, and CAD activities in the M4S6 treatment were significantly greater than those in the M4S4 and M6S6 treatments. Compared with the M4S4 treatment, these variables increased by 12.05%, 11.09%, 21.56%, 11.91%, 18.46%, 16.1%, and 16.84%, respectively, and compared with the M6S6 treatment, they increased by 2.06%, 2.53%, 2.78%, 2.98%, 8.81%, 4.59%, and 4.36%, respectively. The D-M4S6 treatment significantly improved the lodging resistance of soybean and weakened the negative impact of intercropping on soybean yield. Therefore, based on the planting pattern of narrow-wide row maize‒soybean intercropping planting pattern, four rows of maize and six rows of soybean were more effective at improving the lodging resistance of soybean in the semiarid region of western China.

Rhizosphere soil properties of waxy sorghum under different row ratio configurations in waxy sorghum-soybean intercropping systems

To overcome the continuous planting obstacle and promote the sustainable production of waxy sorghum, a two-years field experiment was performed to determine the responses of waxy sorghum rhizosphere soil properties to different row ratio configurations in waxy sorghum-soybean intercropping systems. The treatments included five row ratio configurations, which were two rows of waxy sorghum intercropped with one row of soybean (2W1S), two rows of waxy sorghum intercropped with two rows of soybean (2W2S), three rows of waxy sorghum intercropped with one row of soybean (3W1S), three rows of waxy sorghum intercropped with two rows of soybean (3W2S), and three rows of waxy sorghum intercropped with three rows of soybean (3W3S), and sole cropping waxy sorghum (SW) was used as control. The nutrients, enzyme activities, and microbes of waxy sorghum rhizosphere soil were investigated at the jointing, anthesis, and maturity stages. Results showed that rhizosphere soil properties of waxy sorghum were significantly affected by row ratio configurations of waxy sorghum intercropped soybean. Among all treatments, the performances of rhizosphere soil nutrients contents, enzymes activities, and microbes contents were 2W1S > 3W1S > 3W2S > 3W3S > 2W2S > SW. Compared to SW treatment, the 2W1S treatment increased the organic matter, total N, total P, total K, gram-negative bacteria phospholipid fatty acids (PLFAs), and gram-positive bacteria PLFAs contents and catalase, polyphenol oxidase, and urease activities by 20.86%-25.67%, 34.33%-70.05%, 23.98%-33.83%, 44.12%-81.86%, 74.87%-194.32%, 81.59-136.59%, 91.44%-114.07%, 85.35%-146.91%, and 36.32%-63.94%, respectively. Likewise, the available N, available P, available K, total PLFAs, fungus PLFAs, actinomycetes PLFAs, and bacteria PLFAs contents under the 2W1S treatment were 1.53-2.41, 1.32-1.89, 1.82-2.05, 1.96-2.91, 3.59-4.44, 9.11-12.56, and 1.81-2.71 times than those of SW treatment, respectively. Further, the determining factors of soil microbes were total K, catalase, and polyphenol oxidase for total microbes, bacteria, and gram-negative bacteria, total P and available K for fungus, available N, available K, and polyphenol oxidase for actinomycetes, and total K and polyphenol oxidase for gram-positive bacteria. In conclusion, the 2W1S treatment was the optimal row ratio configuration of waxy sorghum intercropped with soybean, which can improve the rhizosphere soil quality and promote the sustainable production of waxy sorghum.

Nitrogen Promotes the Salt-Gathering Capacity of Suaeda salsa and Alleviates Nutrient Competition in the Intercropping of Suaeda salsa/Zea mays L

Nitrogen accelerates salt accumulation in the root zone of an euhalophyte, which might be beneficial for inhibiting the salt damage and interspecific competition for nutrients of non-halophytes in intercropping. However, the variations in the effect of euhalophyte/non-halophyte intercropping with nitrogen supply are poorly understood. Here, we selected the euhalophyte Suaeda salsa (suaeda) and non-halophyte Zea mays L. (maize) as the research objects, setting up three cropping patterns in order to explore the influence of nitrogen application on the intercropping effect in the suaeda/maize intercropping. The results showed that the biomass of maize in the intercropping was significantly lower than that in the monoculture, while for suaeda, it was higher in the intercropping than that in the monoculture. The biomass of maize under NO₃^--N treatment performed significantly higher than that under no nitrogen treatment. Moreover, under suitable NO₃^--N treatment, more salt ions (Na⁺, K⁺) gathered around the roots of suaeda, which weakened the salt damage on maize growth. In the intercropping, the effect of NO₃^--N on the maize growth was enhanced when compared with the non-significant effect of NH₄⁺-N, but a positive effect of NH₄⁺-N on suaeda growth was found. Therefore, the disadvantage of maize growth in the intercropping suaeda/maize might be caused by interspecific competition to a certain extent, providing an effective means for the improvement of saline-alkali land by phytoremediation.