Orchard grass cultivation originated in the United States in the 19th century, was popularized and applied in the 1940s, and has become a conventional production technology for orchards in most countries. China introduced this technology from the early 1980s, initially applied in orchards in Fujian, Guangdong, Shandong and other places, and began to promote orchard grass as a green fruit production technology nationwide in 1998. After nearly 30 years of research and application, the majority of fruit farmers on the orchard grass in maintaining the stability of the orchard micro-environment, improving soil fertility, improving fruit quality, reducing production costs and other aspects of the understanding continues to increase, orchard grass area continues to increase, orchard grass ecological benefits and economic benefits are becoming more and more obvious, this transformation for the healthy and sustainable development of China's fruit tree industry is of great significance.
At present, most studies have shown that orchard grass can improve soil physicochemical properties, improve soil fertility, enhance and maintain soil microbial and enzyme activities, improve tree nutrition, improve yield and quality, increase orchard biodiversity, and enhance resistance to diseases and insects. However, in view of the lack of systematic research on the comprehensive supporting management measures after orchard grassing, and even the deviation in understanding, the research on the management measures after orchard grassing is summarized in order to provide theoretical support and technical reference for the sustainable and healthy development of orchards in China.
☞ Reaping management
Orchard grass includes two forms: natural grass and artificial grass. Natural grass is mostly selected from local grass species that can form natural communities in the local area, combined with the removal of vicious weeds in orchards, and the retention of benign weeds. Artificial grass mainly selects grass species with strong adaptability, large grass yield, shallow root, short stalk, and conducive to the growth and reproduction of natural enemies of pests, mostly legumes and grasses, which can be planted with single grass species or 2 or more grass species.
At present, orchards are mostly mowed after grass is planted, and the grass is mostly covered in the tree tray or covered in place after cutting. After the grass is planted, the growth amount of grass species can be changed by timely mowing, which regulates the growth and development and succession of grass species, and can also avoid competing with fruit trees for fertilizer and water for a short time, thus alleviating or eliminating the nutrient competition relationship with fruit trees. The period and frequency of mowing are determined according to the standing conditions of the orchard and the growth characteristics of the grass species to ensure that the grass is in a relatively stable state for a long time.
1. The effect of cutting on the growth and development of fruit trees
Although orchard grass has more advantages, it is also easy to form nutrient and water competition with fruit trees, especially the competition of nitrogen nutrition, which inhibits the growth of fruit trees to a certain extent, which is especially obvious in young orchards. Mowing is an effective way to reduce nutrient competition between raw grass and fruit trees.
2. Effect of cutting on orchard soil
The soil directly provides water and mineral nutrients to the fruit trees, which is the basic component of the orchard ecosystem, and the relative stability and healthy development of the soil environment are conducive to the growth and development of fruit trees and the sustainable use of orchards. Orchard grass after mowing can increase the mineral nitrogen content of surface soil, reduce surface runoff and surface runoff mineral nitrogen loss, and its effect of reducing soil erosion is related to the height of mowing, the time of mowing, the number of mowing, etc., which can promote the growth and development of the tree.
Mowing can improve the ecological environment of the orchard near the surface grass, improve the illuminance and temperature of the near surface grass, increase the daily evaporation of the surface, reduce the relative humidity and co2 concentration of the air, which can improve soil permeability in the rainy season, provide a suitable environment for the growth of the root system, and is conducive to the healthy growth of fruit trees. At the same time, the soil bulk density is reduced, and the soil nutrient content is increased, among which the organic matter and total potassium content are significantly increased, and the available potassium content is significantly increased, and with the increase of the age, the multi-nutrient content of mowing cover and mowing burial increases year by year, while the content of some nutrients in clear farming shows negative growth.
3. The impact of mowing on the grassland environment
Mowing can regulate the succession process of grass species, and the cutting time, the number of mows and the height of mowing are determined by the growth height and growth of grass communities, which are related to grass varieties. A reasonable mowing period and number of mows can ensure that the grass cover is in a relatively stable state for a long time. In the Bohai Bay area using artificial planting of red trifoliary apple orchards, the growing season generally needs to be cut 4 to 6 times, the height of stubble retention is about 20cm is appropriate, at this time the net photosynthesis rate of red trifoliary leaves is high, the effective photosynthetic time is long, the number of branches in the base part is large, and the total yield is high, which is conducive to the continuous production of red trifolium. Mowing highly affects the biomass and nutrient composition of grass species. In general, the mowing height of grass species should be above the growth point, and the leguminous grass species should be above 1 to 2 nodes of the stem. Arid and semi-arid areas should appropriately reduce the number of mows, or even no mows.
In addition, mowing can change the number and occurrence of insect populations in orchard ecosystems, and timely mowing can reduce the harm of pests to fruit trees to a certain extent. Compared with the control area of clear farming, the study of ryegrass planting areas can reduce the summer inter-tree temperature and increase the relative humidity of air, so that the field microclimate has been significantly improved, which inhibits the growth of the coniferous claw mite population, which is conducive to the growth of its natural enemy chestnut blunt mite population, and there are differences between different mowing treatments, and the number of coniferous claw mites in the peak period of occurrence on the full-cut tree is 4.78 heads per leaf, and the number of strip cuts is 1.62 heads per leaf.
☞ Fertilizer water management
After grassing, reasonable fertilizer water management and timely removal of malignant weeds can make the grass community quickly form a dominant grass cover, increase the coverage and biomass of grass species, and especially alleviate the problem of fertilizer competition between grass and fruit trees in young orchards. After the grass is planted, reasonable fertilization can improve the physical and chemical properties and nutrient status of the soil, promote the growth and development of fruit trees, and improve fruit yield and quality.
Balanced fertilization under raw grass cover conditions can improve the fruit set rate and fruit shape index, significantly increase the soluble sugar content and vitamin C content of fruit, significantly improve the water use efficiency of fruit trees, and can increase the rain accumulation at the ripening stage and increase the soil storage capacity; the soil organic matter content and fast-available nutrient content under the combined fertilization treatment of raw grass cover are higher than those of raw grass control and single fertilization treatment. Fertilization treatment after grass planting can increase the soil moisture content of 0~30 cm soil layer, reduce soil pH value, and increase soil organic matter content, indicating that fertilization can promote grass growth and dry matter accumulation.
In addition, the content of soil organic carbon, microbial volume carbon, dissolved organic carbon and easily oxidized organic carbon was increased after fertilization after grassing; the activities of soil sucrase, cellulase and β-glucosidase increased; the diversity of soil microbial communities was significantly improved, and the utilization rate of soil microorganisms on carbohydrates, amino acids and polymer carbon sources was significantly increased, of which the effect of nitrogen fertilizer application was more obvious.
After the grass is planted, it cooperates with reasonable fertilizer and water management to show positive effects on the soil environment, soil water use efficiency, tree growth and development, fruit yield and quality of the orchard. Research in this regard should be strengthened, combined with the fertilizer water management of fruit trees, and the fertilizer and water management measures adapted to local grass orchards should be screened to facilitate the long-term healthy development of orchards.
☞ Other management
After 4 to 5 years of grass in the orchard, the grass cover begins to age, and the soil surface layer is compacted, which is not conducive to the growth and development of the root system of the fruit tree and its absorption of nutrients, and the grass cover should be updated in time. At this time, it should be combined with rotary tillage or ploughing management, clearing and ploughing for 1 to 2 years, and then re-planting grass.
It is recommended that phosphorus and potassium fertilizers be supplemented in orchard management in a timely manner, and alkaline substances such as lime can be added to reduce the decline in soil pH caused by leguminous forage when cultivating fertilizer. In addition, should be combined with fruit tree disease and pest control measures, the ground grass is sprayed to control diseases and insect pests, generally natural grass due to the rich diversity of population diversity, its grass cover diseases and insect pests are lighter, and the population structure of a single artificial grass formed by the grass quilt is more prone to diseases and insect pests, should pay attention to timely control.
☞ Looking ahead
Orchard grass is a long-term and systematic project in orchard management. Due to its obvious advantages in cultivating fertility in orchards, improving tree growth and development, improving fruit tree yield and fruit quality, increasing orchard microsystem biodiversity and reducing the occurrence of diseases and insect pests, it has received more and more attention from the majority of scientific and technological workers and fruit farmers, and the research and investment in orchard grass has gradually increased. Strengthening the research on post-grass management measures in orchards and adopting practical and feasible management measures to adapt to local orchard conditions can improve the stability of orchard ecosystems and contribute to the long-term healthy and stable development of orchard ecosystems.
Ming Ming: Excerpted from "China Fruit Trees", No. 4, 2018, "Post-weed Management Measures and Their Research Progress in Orchards in China" (Xu Tianwei, Qin Sijun, Du Guodong, Lü Dede)