Kiwifruit is a berry-like vine fruit tree, an emerging fruit with high nutritional value. Native to the Yangtze River basin in China, it is cultivated in Henan, Shaanxi, Hunan, Sichuan and other provinces. While its fruit edible value and medicinal value are very high, and its tree ornamental value is also very high. Therefore in recent years, the cultivated area has been expanding year by year.
A、Fertility characteristics of kiwifruit
1、Nutritional growth characteristics of the root system
The roots are fleshy, white at first and then light brown. Older roots have a gray-brown outer skin and red inner flesh. While the main roots are not developed, and the fibrous roots are numerous, shallow and widely distributed. However mostly distributed in the 50 cm topsoil layer. The ducts of the roots are well developed, and the root pressure is large, with a strong ability to transport nutrients. While it is easy to produce adventitious roots and has a strong regenerative capacity.
The root system of kiwifruit penetrates extremely well. It can penetrate rock crevices or semi-weathered mother rocks and extend downhill to areas with deep soils and concentrated water and fertilizer. The annual growth cycle of kiwifruit roots is longer than that of branches, and there are two peaks in the annual cycle. The first peak occurs in June when the branch tips grow rapidly. The second occurs in September, late in fruit development. Root growth and above-ground growth are alternating and have some regular changes.
2、Nutritional growth characteristics of branches and leaves
Kiwifruit is a deciduous vine trailing fruit tree. The top of the branches and vines grow in an anti-clockwise twining pattern. It generally grows nearly twice a year, and rarely three times. The vines are about 10 m long, with one to several main vines. According to the growth and fruiting or not, it can be divided into two kinds of fruiting branches and nutritional branches.
3、Kiwifruit fertilizer requirements characteristics
① Requirements for soil conditions
Kiwifruit is adapted to warm, moist, slightly acidic soil. Most afraid of sticky, strongly acidic or alkaline, poorly drained, excessively dry, infertile soil. Therefore, measures can be taken to improve the physical and chemical properties of the soil and to create an optimal ecological environment for its growth.
②Fertilizer demand characteristics
The kiwifruit grows vigorously, with lush foliage and many early fruits. As a result, a large amount of nutrients are consumed each year. The effective nutrients in the soil are not sufficient to meet its needs. Therefore, it is necessary to grasp its fertilizer requirements in a timely and accurate manner to achieve scientific and economic fertilization.
a、Phosphorus nutrition and fertilization
Phosphorus enhances the vitality of kiwifruit, promoting flower bud differentiation, fruit development and seed maturation. It also enhances quality, promotes root expansion and drought and cold resistance. In kiwifruit orchards with increased application of calcium superphosphate and organic fertilizers, phosphorus deficiency symptoms are rarely seen.
b、Potassium nutrition and fertilization
The right amount of potassium promotes fruit fertility and ripening, sugar conversion and transport. It also improves fruit quality and storage resistance. It can also promote thickening growth and tissue maturation, and enhance the tree’s resistance to stress.
Potassium deficiency is a nutrient disorder that occurs more commonly. In many cases, potassium deficiency causes foliar symptoms that are mistakenly attributed to drought or wind damage. Typically kiwifruit contains 1.8% to 2.5% potassium. If it drops below 1.5% it will show symptoms of potassium deficiency. The application of potassium fertilizer should be taken seriously in production. As kiwifruit requires a high chloride content for growth. Therefore, it is better to apply potassium chloride.
c、Calcium, magnesium and sulfur nutrition and fertilization
Calcium plays an important role in cell wall composition, regulates photosynthesis and is closely related to membrane stability and permeability. Suitable calcium content can delay fruit aging, improve hardness and enhance storage resistance.
Magnesium can regulate photosynthesis and hydration of plants. The right amount of magnesium can promote fruit fertility and improve quality.
Sulfur is a variety of amino acids and enzymes components, and carbohydrates, fats and protein metabolism has a close relationship.
d、Micronutrient nutrition and fertilization
Chlorine is related to photosynthesis and hydration. Kiwifruit is sensitive to chlorine deficiency and begins to show a patchy loss of green at the top of the old leaves between the main and lateral veins scattered, expanding from the leaf margin to the main and lateral veins. In areas with high rainfall, chlorine is easily lost by leaching from the soil. Leaves containing less than 0.6% of dry matter weight will show symptoms and should be supplemented with potassium chloride fertilizer.
4、Summary of the fertilizer needs of kiwifruit
In summary, kiwifruit has a high need for all types of mineral elements. At the same time, the uptake of various nutrients varies considerably in different reproductive stages. From early spring budding to fruit set, nitrogen, phosphorus, potassium, magnesium, zinc, copper, iron and manganese accumulate in the leaves at about 80% of the annual total. During the fruit expansion period, nitrogen, phosphorus and potassium nutrients are gradually transferred from the branches and leaves to the fruit. According to leaf analysis, kiwifruit has a special preference for chlorine. It is about 0.025% for general crops and 0.8% to 3.0% for kiwifruit. There is a greater demand for chlorine especially when potassium is lacking.
B、Fertilization techniques for kiwifruit
① Base fertilizer
Generally advocate the application of base fertilizer in autumn, early application after fruit harvesting is more favorable. Early application of basal fertilizer plus appropriate irrigation. To accelerate the recovery and maintenance of leaf function, delay leaf senescence, growth of leaf life, to maintain a strong photosynthetic production capacity, has an important role. Therefore, autumn basal fertilization increases the level of stored nutrients in the tree. It facilitates the differentiation of flower buds before and after leaf drop and for a period before flowering the following year. It facilitates budding and new shoot growth. The quality of flowering is good, which in turn facilitates pollination and fruit set.
The application of base fertilizer should be combined with soil improvement and soil fertility. More organic fertilizer should be applied, such as stable manure, compost, cake fertilizer, human manure and urine. At the same time, adding a certain amount of fast-acting nitrogen fertilizer, according to the orchard soil nutrients can be applied with phosphorus, potassium fertilizer. The amount of base fertilizer should account for 60% of the annual fertilizer application. If applied in winter and spring, it can be reduced appropriately.
Fertilization required in a timely manner according to the root growth characteristics of kiwifruit and the above-ground growth phenology. Too early or too late is not conducive to normal tree growth and fruiting.
We usually apply it in February and March around the time of sprouting. Fertilization at this time can promote the sprouting of axillary buds and the growth of branches and leaves, and improve the fruit set rate. Fertilizer is mainly fast-acting nitrogen fertilizer, together with potassium fertilizer, etc.
b、Fertilizer for strong fruit and tip
Generally in June to August after the flowering. This stage of rapid expansion of young fruit, new growth and bud differentiation need a lot of nutrients. We can fertilize one to two times as appropriate according to the tree’s strength and fruiting volume. Fertilization during this period requires the application of nitrogen, phosphorus and potassium fertilizers in combination. Also pay attention to observe whether there is a lack of vegetation symptoms, so that timely adjustment.
2、The amount and proportion of fertilizer application
According to the size of the kiwifruit tree and the number of results, as well as the effective nutrient content of the soil and other factors flexible control. We generally apply it in two applications, in early spring in February and in autumn in August after fruit harvest. Compost, cake fertilizer, stall fertilizer and chlorine fertilizer are the main ingredients, with appropriate amounts of urea, phosphorus fertilizer and grass ashes.
3、Kiwifruit fertilization methods
①Root fertilization method
a、Fertilization by circular furrow
At the outer edge of the kiwifruit crown projection or 1 meter from the trunk, dig a circular ditch 30~40 cm deep and wide to apply fertilizer.
b、Radial ditch application
With the trunk as the center of the circle, dig 4~6 radial ditches at about 40 cm inside and outside the crown projection in the direction of horizontal heel growth. Width 30 cm, depth 30 ~ 40 cm. Inside shallow and outside deep, so as not to hurt the roots too much. Mix fertilizer and soil into the ditch.
c、Strip trench fertilization
Dig a trench 30 cm wide and 30~40 cm deep on each side of the outer edge of the crown projection. Then, apply fertilizer.
Dig a hole 40 cm deep and 40~50 cm in diameter under the tree crown 1 m away from the main trunk. The number depends on the size of the tree crown and the amount of fertilizer. Then, apply the fertilizer.
Spread the whole garden and then turn it 20~30 cm deep.
Also called extra-root fertilization. It is to spray a certain concentration of water soluble fertilizer evenly on the leaves. Fertilizer method outside the root is simple and easy, with a small amount of fertilizer, fertilizer effect is fast. This can avoid the loss of certain nutrients fixed or leached in the soil. When we apply foliar sprays, we need to distribute the fertilizer evenly over the canopy, with little influence from the nutrient distribution center. Again, we can do this in combination with spraying and sprinkler irrigation. This saves labor and reduces costs.
The types and concentrations of fertilizers commonly used for foliar spraying of kiwifruit include the following: urea 0.3% to 0.5%, ferrous sulfate 0.3% to 0.5%, boric acid or borax 0.1% to 0.3%, potassium sulfate 0.5% to 1%, calcium sulfate 0.3% to 0.4%, grass ash 1% to 5%, and potassium chloride 0.3%.
We prefer to apply foliar fertilizer in the morning and evening on cloudy or sunny days when there is no wind.