The result of the "big and small year" is a phenomenon that is easy to appear in the production of walnuts in the fruiting period, which not only causes a decline in fruit yield, poor nut quality, and a decrease in economic income, but also easily leads to weak tree strength, reduced stress resistance, aggravated pest damage, and even shortened the productive life of walnuts. Directly affect the yield of walnuts in the current year.
The cause of the occurrence
1. Night frost hazards. Spring late frost is the main disaster affecting the yield of walnuts in Shangluo. In recent years, with the global warming of the climate and abnormal atmospheric circulation, the probability of late frost in early spring has increased significantly, and a late frost will occur every 2-3 years. Late frost generally appears in the first and middle sentences of April, at this time it is the early stage of walnut germination, leaf spreading and flowering, after the late frost hazard, the stamens dry out and lose the ability to pollinate, the pistil stigma turns black and loses the ability to fertilize, the surface of the young fruit appears ring-shaped black spots, the young buds and young leaves dry and die, and the tree momentum weakens, thus affecting the yield and nut quality of the year, forming a small year of fruit. At the same time, it also has a certain impact on normal growth and yield in the second year.
2. Persistent drought. Walnuts like to be moist, winter, spring drought or early summer drought, drought continuous occurrence, due to excessive drought of the soil, resulting in water imbalance in the tree body, water deficit occurs, resulting in leaf drooping, wilting, fruit growth is hindered and a large number of flowers and fruits fall, resulting in small results.
3. Nutritional imbalance. In the large year of excessive load, due to the growth and development of the fruit and the consumption of a large amount of nutrients, resulting in the growth of the tree is weak, unable to form flower buds, resulting in a decrease in the amount of flowers in the following year and the formation of a small year with a small fruit and a small year with a lighter load, due to the fruit growth and development consumes less nutrients, which is conducive to the differentiation of female flower buds and lays the foundation for a large number of results in the next year.
4. Variety differences. Under the circumstance that the natural conditions and cultivation management level are basically similar, the size of the walnut fruit fall rate mainly depends on the biological characteristics of the variety, and the varieties with high fruit fall rate are prone to the phenomenon of large and small annual results.
5. Serious pests and diseases. These include walnut erector moth, peach borer borer, walnut cross-groove elephant, walnut flat leaf beetle and walnut black spot disease, walnut brown spot disease, walnut anthrax, walnut branch blight, walnut root decay, etc.
6. Plastic trimming is unreasonable. Failure to pay attention to plastic trimming, or improper pruning methods, will lead to the occurrence of large and small annual results.
7. Fertilizer water management is not in place. Fertilization is single, the fertilization time is unreasonable, and the tree body cannot continuously supply nutrients. During the differentiation of female flower buds, flood irrigation or heavy application of nitrogen fertilizer causes new shoots to flourish, and nutritional competition occurs with adult flowers, so that flower bud differentiation lacks nutrients.
Prevention and control methods
1. Choose varieties with strong stress resistance.
2. Reasonable shaping and trimming. Timely remove overcrowded branches, overlapping branches, intersecting branches, diseased and insect branches, and maintain the coordination and balance of tree shape; Combining thinning and slow release, appropriately reducing peripheral branches and controlling the apex advantage; Pressure outside the internal, pressure before and after, to maintain three-dimensional results; Retract the weak backbone branch, raise the angle, and ensure that the backbone branch is strong; Timely culture and update of fruiting branches. Through plastic pruning, the relationship between growth and results is adjusted, light conditions are improved, the phenomenon of large and small years is overcome, and the productive life is prolonged. After pruning, spray with ulcer healing agent + garlic essential oil to promote wound healing and kill virus bacteria.
3. Flower preservation and fruit preservation and flower thinning. Flower preservation and fruit thinning is one of the basic measures to effectively prevent the annual fruit phenomenon of walnut size.
4. Fertilize and irrigate. After the autumn leaves fall, combined with ploughing and expanding the plate, the radial furrow application method is adopted, and the plant is fertilized. In the spring, before germination and the hardcore stage of the fruit, the plant is fertilized with compound fertilizer. After fertilization, water the overwintering water once before the soil is frozen, and water the soil in time after thawing to reduce the ground temperature to delay the flowering period and prevent frost. At the same time, according to the soil moisture and walnut growth and development law, timely irrigation.
5. Control of pests and diseases.