How should chestnuts be top-dressed in early spring for high yields?
Chestnuts have long enjoyed the reputation of “king of dried fruits”. As an economic forest crop, they have expanded economic opportunities for farmers in mountainous areas and become one of the channels for some mountain farmers to prosper, but for chestnuts to yield high, early spring top-dressing has its particularities!
I. Key points of base fertilizer for chestnuts
Chestnut trees have a relatively large fertilizer requirement, and rational fertilization is an important foundation for a high-yielding chestnut orchard. Base fertilizer should be mainly farmyard manure, so as to improve the soil, enhance the soil's ability to retain fertilizer and water, and provide relatively comprehensive nutrient elements.
When planting chestnut trees in blocks on flat land or gently sloping land, pits 0.8-1.0m long and wide and about 0.5m deep need to be dug. For each pit, apply 50-100kg of fully mixed decomposed organic fertilizer, 0.5-0.6kg of urea, and 0.4kg of ordinary superphosphate. For soil with low boron content, 10-15g of boron fertilizer should also be applied per pit as base fertilizer.
II. Key points of top-dressing for chestnuts
1. Types of top-dressing
Chestnut top-dressing should be mainly quick-acting nitrogen fertilizer, combined with phosphorus and potassium fertilizers.
2. Timing of top-dressing
Top-dressing is done in early spring and summer. In spring application, generally apply 0.3-0.5kg of urea per newly planted fruit tree, and 2kg of urea per large tree in full fruit stage. After top-dressing, combine with watering to fully bring out the fertilizer effect.
Summer top-dressing is carried out from late July to mid-August. At this time, applying quick-acting nitrogen fertilizer and phosphorus fertilizer can promote fruit enlargement, plump flesh, and improve fruit quality.
3. Number of top-dressing applications
Foliar top-dressing can be carried out multiple times a year, with 2 times being especially important.
The 1st time is in early spring when the leaves at the base of the branches have just unfolded and are turning from yellow to green; spray 3-5g/kg urea plus 3-5g/kg borax. Its role is to promote basic leaf function, improve photosynthesis, and promote flower bud formation.
The 2nd time is 30d before harvest, spraying 1g/kg monopotassium phosphate twice at an interval of 10-15d. Its main role is to improve photosynthetic efficiency, promote the transfer of nutrients from leaves and other organs into the fruit, and it has an obvious effect of increasing single-grain weight.
III. Why fertilize before harvesting chestnuts?
Chestnuts have a long fruit-bearing period and a large fruit load, consuming many nutrients. Before and after the fruit ripens, the tree vigor is already in a hungry or semi-hungry state and is very weak, which is unfavorable for flowering and fruiting the next year. If pre-harvest and post-harvest fertilizer can be applied in time to supplement nutrients, then tree vigor recovery can be accelerated and the trees can be strengthened, laying a good foundation for high and stable yields the next year.
Apply post-harvest fertilizer within 5-10 days after harvesting the chestnuts, mainly with nitrogen-phosphorus-potassium compound fertilizer and high-quality organic fertilizer. If the weather is dry, after fertilizing, drench each tree with 80-100 kilograms of clear water or decomposed and rotted human and livestock manure water, so as to promote fertilizer dissolution and transformation, supply root absorption and utilization, and improve the fertilization effect.