What are the remedial measures for a kiwifruit orchard after heavy rain and flooding?
After the heavy rain, kiwifruit plants are submerged and buried. Kiwifruit has fleshy roots. Excessive rain causes soil water saturation, insufficient nutrient supply and poor aeration, weakening the root respiration capacity, and the roots will gradually rot. During rainfall, if rainwater remains on the soil surface for 2 hours, the leaves will yellow and curl slightly; if it remains for 3-4 hours, slight root rot begins to appear, and leaf yellowing and curling worsen; if it remains for more than 5 hours, the roots rot severely, and the edges of the aboveground leaves scorch and fall off; after 4 days of flooding, 40% of the plants die, and after 8 days, basically 100% die. In order to help the affected orchard resume growth as quickly as possible and reduce flood damage losses, it is recommended that affected orchards take the following remedial measures. Let us take a closer look:
1. Quickly clean up and tidy the orchard
After heavy rain and flooding, growers should quickly organize personnel to clean up and tidy the orchard. First, straighten the fruit trees and trellis posts, and promptly cover exposed roots with fresh soil. Second, remove silt and rubble from the bed surfaces and bed furrows in the orchard, dredge the ditches inside and outside the orchard, strengthen drainage within the orchard, ensure there is no standing water in the bed furrows, and make the orchard dry after the rain. Third, repair damaged trellis materials and comb the branches and vines so that damaged plants can be re-trained onto the trellis. Fourth, prune broken and damaged branches and leaves. For plants soaked by rainwater for more than 48 consecutive hours, remove some fruit, prune young tender shoots and excessively vigorous branches, and appropriately cut back weak branches to reduce the tree's load. Fifth, for bagged fruit that has been submerged by floodwater, remove the paper bags promptly.
2. Disinfect the whole orchard and apply additional foliar fertilizer
Be sure to seize the opportunity when the weather clears after the heavy rain to spray the whole orchard carefully 2-3 times with efficient fungicides and foliar fertilizers.
How to use the fungicides and foliar fertilizers: 1000 times 45% amobam + 1000 times 2% amino-oligosaccharin + 400 times amino acid liquid fertilizer, or 500 times 20% sodium dichloroisocyanurate + 1000 times fruit vaccine + 300 times super phosphorus and potassium. The two methods can be used alternately. They mainly prevent and control canker and early leaf drop disease, and improve plant resistance and fruit quality.
Plant care: For plants soaked by rainwater for more than 48 consecutive hours, dig open the soil around the root crown and air the roots. Carry out inter-row tillage and weeding in the tree dish, and loosen the soil to drain moisture. When the soil begins to dry, use 2500 times Yitushi solution + 500 times 70% thiophanate-methyl, or 2000 times Aierjia solution + 500 times 70% thiophanate-methyl for root drenching, with about 5 kg of liquid per plant, to promote new root growth and tree recovery.
Precautions: Heavy rain will cause a large amount of staining and damage to kiwifruit leaves, fruit and trunks. Where conditions permit, a high-pressure sprayer should be used to apply fungicides and foliar fertilizers, using water pressure to wash the trees clean. In orchards with a high incidence of major diseases such as kiwifruit canker, phytophthora rot and root rot, spraying must be meticulous and thorough, and the whole orchard should be sprayed, including the ground, trunks and so on.
1. Dig ditches for drainage. Drain promptly during rainfall. After the water recedes, if standing water remains in low-lying areas of the orchard, ditches must be opened promptly to drain it and restore normal respiration of the trees.
2. Loosen the soil and fertilize throughout the orchard. After flooding, the orchard soil becomes compacted, causing root hypoxia. When the surface soil no longer sticks to the foot when stepped on, carry out shallow tillage to loosen the soil and promote new root growth. After loosening the soil, apply fertilizer in a timely manner according to tree vigor, tree age and yield, applying 2500 kg to 3500 kg of organic fertilizer per mu, together with 80 to 100 kg of special fruit tree fertilizer or 150 kg of compound fertilizer, depending on tree size.
3. Moderate pruning. For trees that lost their leaves after the disaster, prune dead branches in a timely manner. Prune away dead branches, diseased and pest-damaged branches, crossing branches, densely growing branches and weak slender branches from the whole tree, so that the tree is well ventilated and lit and its metabolism is balanced.
4. Whitewash the trunks. Leaf drop is likely after waterlogging, so trunks can be whitewashed. Whitewash formula: 10 parts water, 2 parts quicklime, 0.5 part salt, 1 part solid lime sulfur mixture, or 25 grams sulfur powder.
5. Spray foliar fertilizer to strengthen tree nutrition and speed up recovery of tree vigor. A solution of 0.2% urea + 0.5% monopotassium phosphate can be sprayed on the leaves once every week for 2-3 consecutive times.
6. Disease prevention. Diseases tend to occur after standing water. Spray 800 times carbendazim or 1000 times thiophanate-methyl on the leaves to control pathogen growth and avoid further harm to the health of the fruit trees.
7. After flooding, as soon as weather conditions permit, spray reactive oxygen species scavengers to alleviate waterlogging damage. A 1000 ppm sodium benzoate or ascorbic acid solution and other reactive oxygen species scavengers can be sprayed on the leaves.