Effect of continuous overcast and rainy weather on the growth of citrus in autumn and its countermeasures

Effect of continuous overcast and rainy weather on the growth of citrus in autumn and its countermeasures

Dangyang City, Hubei Province is the dominant planting area of wide-skinned citrus in China. The existing citrus planting area is 21,000 hm ~ 2. The main citrus types are Wenzhou mandarin and Ponkan, among which Ponkan (E mandarin No. 1, Qianyang seedless) has an area of 14,000 hm ~ 2. A series of abnormal weather conditions occurred in Yichang in the autumn of 2017. In this paper, the effects of abnormal climate on the growth and fruit setting of citrus in Dangyang in autumn 2017 were investigated and analyzed, and some countermeasures were put forward.

1 abnormal weather in autumn 2017

From September 18 to October 19, 2017, there was an obvious continuous rainy weather process in Dangyang, which lasted for 30 days, and the daily average temperature was 18.6 ℃, which was 1.4 ℃ lower than that in the same period of previous years, and the number of continuous precipitation days was 28 days, 10 days more than the longest continuous precipitation days, and the precipitation reached 238.5 mm. It is 3.1 times that of the same period in previous years (77.1 mm); the average relative humidity is 92%, which is significantly higher, and the sunshine hours are 7.4h, only 5% for the same period (148.1 h). The occurrence of abnormal weather has a great impact on the fruit quality of citrus and the normal growth and growth of plants before winter. In this regard, it is particularly important and urgent to correctly analyze the impact of abnormal weather on citrus production in order to implement the corresponding measures in time.

2 examples of observation and test

In October 2017, a comparative observation was conducted in two groups of Wang Yisheng orchards in Universe Village, Banyue Town, the main citrus producing area of Dangyang City. The existing orchard is 4 hm2, mainly wide-skinned citrus. (4) the hm2 orange orchard was treated with ditching, cleaning, spraying, fertilization, shoot removal, whitening and so on. 667 m2... No processing has been done. Comparative test time: September 20, 2017 ~ … February 2018.

3 observation test results

3.1 Test results

The observation results of fruit trees with and without protective measures during the experiment are shown in the attached table.

Attached observation results

3.2 main harm of continuous rainy weather to citrus growth in autumn

The main results are as follows: (1) when the long-term overcast and rainy weather occurs, the poor drainage of the orchard will lead to insufficient oxygen supply to the root growth point, the respiration is weakened, it is difficult to transport nutrients normally, and the root growth point necrosis occurs seriously, which weakens the tree potential. At the same time, continuous overcast and rain will lead to a large number of trace element loss and absorption obstacles, especially the rising water in roots will lead to the reduction of copper and zinc absorption, aggravate the lack of elements, and seriously lead to fruit drop and fruit cracking.

(2) there is more moisture in the tree, the branches grow vigorously, the accumulated temperature decreases, and the fruit ripening period is delayed. The accumulation concentration of nutrients in leaves and buds decreased accordingly, which affected the quantity and quality of flower bud differentiation and reduced yield in the coming year.

(3) the continuous overcast and rainy weather greatly reduced the photosynthesis of citrus, decreased the synthesis of carbohydrates, increased the moisture of pulp, affected the sweetness and flavor, and made the peel more fragile and tender, not easy to transport and store, and easy to rot fruit.

(4) the continuous rainy weather leads to high humidity in orchard, poor soil permeability, decrease of tree nutrient accumulation and decrease of resistance to diseases and insect pests. It is easy to cause a large number of mature citrus fruits, such as black spot, brown rot, anthracnose, green, green mold, tick and so on.

(5) reduce the frost resistance of citrus.

4 to deal with technical measures

4.1 timely implement the technical measures of "first prevention, second clearing, and three increases". The first prevention is to make good use of the sunny weather after the rain to carry out a thorough disease prevention and control work in the whole park. In view of the occurrence and development trend of orchard diseases in Dangyang City, biophysical prevention and control measures such as solar energy insecticidal lamp, armyworm color plate, predator mite, trap can and trunk adhesive tape are mainly adopted, combined with the necessary low-toxic and efficient pesticide emergency prevention and control. for example, fungicides such as prochloraz + ethylphosphate aluminum or topiramate + ethyl phosphate aluminum are sprayed once a week twice a week for effective prevention and control.

Erqing means clearing ditches and draining stains in time after rain, reducing orchard humidity, and removing fallen fruits, diseases and insect pests, split fruits, branches and leaves of diseases and insect pests, weeds, etc., so as to create a clean orchard environment and keep the soil moderately dry and ventilated. to ensure the normal growth of citrus roots and the absorption of soil minerals.

The third increase is the timely application of trace elements in fine weather after rain to improve the stress resistance of trees. Studies have confirmed that continuous overcast and rain will lead to a large loss of trace elements and absorption obstacles, especially the rising water of roots will lead to the decrease of copper and zinc absorption, aggravation of element deficiency, and aggravation of serious fruit drop, fruit cracking, anthracnose and brown spot. Therefore, as an emergency prevention and control measure, a large area of orchard zinc and potassium supplement should be carried out, 0.2% zinc sulfate should be sprayed 1-2 times, and 0.08% copper sulfate should be sprayed in orchards with heavy fruit cracking, withered branches and gum flow.

4.2 timely implementation of the technical measures of "one increase, two thinning"

One increase is the application of overwintering fertilizer to the late-maturing variety garden, which is mainly organic fertilizer, combined with phosphorus and potash fertilizer. The main source of organic fertilizer is farm manure, biogas slurry, residue grass and forest surface humus, supplemented by high quality commercial fertilizer. Generally, adult normal fruit trees are treated with commercial organic fertilizer 1.5 ~ 2.0 kg, high quality and low nitrogen compound fertilizer 0.5 kg. The depth of fertilizer trough is 25 ~ 30 cm, and it is evenly applied in layers, and the trough is curved. The second thinning is to remove the diseases and insect pests, deformed fruits and extra small fruits on the tree in time to ensure that the tree carries fruit reasonably; to remove redundant and overdense shoots, especially late autumn shoots, to create good ventilation and light transmission conditions for orchards to the maximum extent.

4.3 implement shallow ploughing and pressure fertilizer in time to reduce humidity and increase oxygen

Methods: combined with green manure and weeds, shallow ploughing for 15 ~ 20 cm was beneficial to increase soil organic fertility, accelerate the evaporation of excess soil water, and protect trees and roots into the physiological preparation period before overwintering.

4.4 do a good job in clearing the garden in winter

The first is spraying the whole orchard, which is mainly composed of mineral agents such as stone sulfur mixture, pine alkali mixture, engine oil emulsion and so on, to minimize the base of diseases and insect pests; the second is to turn the whole orchard deeply to improve the soil environment of the orchard; the fourth is to prune the whole orchard timely and appropriately, mainly to cut off the branches of diseases and insect pests, over-dense branches, senile branches and drooping branches, so as to improve the ventilation and light transmission of the orchard to the maximum extent. Fifth, according to the weather conditions, in case of strong cold air invasion, we can take physical measures such as canopy mulching, underground mulching, timely irrigation and other physical measures to keep the trees and fruits safe through the winter.