Effects of Wheat and Broad Bean Catch Crop and Their Decomposed Liquids on the Growth and Blight of Continuous Cropping Pepper Seedlings

To clarify the effects of catch crop decomposition liquid on the growth and blight of continuous pepper seedlings, and to provide the theoretical basis and technical support for wheat and broad bean catch crop to alleviate the continuous cropping obstacles of peppers.

Pepper and pepper continuous cropping soil were used as the research object. Firstly, seven catch crop treatments were set up, including wheat (A), broad bean (B), large-leafed skunk cabbage (C), wheat and broad bean mixture (AB), wheat and large-leafed skunk cabbage mixture (AC), broad bean and large-leafed skunk cabbage mixture (BC), and wheat, broad bean and large-leafed skunk cabbage mixture (ABC), and the non-catch crops were used as the control (CK). Study the effects of different treatments on the pepper growth and blight. Secondly, in order to ascertain the role of its catch crop decomposition liquid in promoting growth and disease control, four treatments with different concentrations of wheat and broad bean mixture straw decomposition liquid (0.01, 0.03, 0.05, and 0.07 g·mL^-1) were set up to investigate different treatments the effects on the growth and blight of pepper seedlings, using distilled water as the control (CK).

When transplanting for 20 and 30 d, the fresh weight of the whole plant, dry weight of the whole plant and plant height of pepper after mixed catch crop treatment of wheat and broad bean were significantly higher than those no-catch crops treatments, and the incidence and disease index were significantly lower than those no-catch crops treatments. The disease index of the wheat and broad bean mixed catch crop treatment was significantly lower than that of all other treatments. The whole plant fresh weight of pepper was significantly increased at 20 d and 30 d of treatment with wheat and broad bean mixed straw decomposed liquids. At 30 d, the dry weight of the whole pepper plant was significantly increased except for 0.01 g·mL^-1 treatment. Compared with distilled water treatment, 0.03 g·mL^-1 treatment significantly increased the root length, average diameter of roots, root surface area, root volume, root tip number and leaf peroxidase (POD) and polyphenol oxidase (PPO) activities of pepper (P<0.05). The mycelial diameter, zoospore germination rate and sporulation yield of Phytophthora capsici treated with different concentrations of wheat and broad bean mixture straw decomposed liquids were significantly lower than those of distilled water treatment (P<0.05). The mycelial diameter and zoospore germination rate of 0.03 g·mL^-1 treatment were significantly lower than those of other treatments, and the inhibition effect of 0.03 g·mL^-1 treatment on phytophthora blight and blight was the best.

The mixed catch crop of wheat and broad bean had a growth-promoting and disease-inhibiting effect on continuous cropping pepper seedlings, and its straw decomposed liquids played an important role in which the decomposed liquids concentration of 0.03 g·mL^-1 when the best effect, and its role was closely related to the direct inhibition of the phytophthora blight and improved the activity of the plant defense enzymes.