Detailed Explanation of Key Technical Points for Soil Testing and Formula Fertilization of Chestnut Trees
1. Main branch balancing (taking the three-main-branch open-center shape as an example). The main branches are the primary framework supporting all the branches. Before pruning, first carefully observe the orientation and growth vigor of the three main branches, have a clear picture in mind, and then make adjustments. For strong and vigorous main branches (with a large thickness ratio), strongly pull them to a wide angle, or use a side branch to replace the main branch extension head, combined with ring barking...
1. Fertilizer requirements: During the annual growth cycle, from the differentiation of male flowers in early spring to the period of flowering and fruit setting, nitrogen demand is greatest, followed by potassium, with less phosphorus; from after flowering to the fruit expansion stage, phosphorus demand is greatest, followed by nitrogen and potassium; from the fruit expansion stage to harvest, potassium demand is greatest, followed by nitrogen, with less phosphorus. In addition to the three major elements nitrogen, phosphorus, and potassium, chestnut trees also need appropriate amounts of calcium, magnesium, and trace elements such as manganese, zinc, and boron. If the supply is insufficient, poor leaf growth and a high rate of empty burs will occur.2. Fertilization technology: Under medium fertility levels, the annual fertilization amount per mu for chestnut trees during the growth cycle is 3000-3500 kg of organic fertilizer or 400-450 kg of commercial organic fertilizer, 14-16 kg of nitrogen fertilizer, 6-7 kg of phosphorus fertilizer, and 7-9 kg of potassium fertilizer. Organic fertilizer is used as base fertilizer; nitrogen and potassium are divided into base fertilizer and two topdressings; phosphorus fertilizer is all applied as base fertilizer; chemical fertilizer and farmyard manure (or commercial organic fertilizer) are mixed and applied.
Base fertilizer: The base fertilizer is mainly organic fertilizer, combined with an appropriate amount of chemical fertilizer. Apply 3000-3500 kg of farmyard manure or 400-450 kg of commercial organic fertilizer per mu, 5-6 kg of urea, 13-15 kg of diammonium phosphate, and 4-5 kg of potassium sulfate. Topdressing: Topdressing at the germination stage: apply 11-13 kg of urea and 6-8 kg of potassium sulfate per mu. Topdressing at the fruit expansion stage: apply 9-10 kg of urea and 4-5 kg of potassium sulfate per mu. Foliar topdressing: During the growth period from May to July, spray a mixture of 0.05% manganese sulfate and 0.05% magnesium sulfate to supplement trace elements. Spraying a 0.1%-0.2% borax solution at full bloom has a certain effect on solving empty chestnut burs. It only needs to be applied to the roots or sprayed once a year; use boron fertilizer with caution in dry years.