How to judge the lack of fertilizer in crops? What are the misunderstandings in the use of fertilizer? How to improve fertilizer efficiency?

Fertilizer is inseparable from the growth of crops, and it is easy to use, so it is deeply liked by farmers, but there are many misunderstandings in the use of fertilizer, which can not improve the fertilizer efficiency correctly. Improper application of fertilizer is easy to cause waste and fertilizer damage. Let's take a look at how to judge whether crops are short of fertilizer, and how to avoid some misunderstandings in the use of fertilizer and improve fertilizer efficiency.

1. How to judge the symptoms of crop fertilizer deficiency

The growth and development of crops need a variety of nutrient elements, once the lack of certain nutrients, it will first show symptoms of element deficiency in the leaves. The lack of different nutrient elements shows different symptoms, and any kind of deficiency will affect the normal growth and development of crops. Therefore, it is necessary to correctly diagnose the symptoms of element deficiency according to its external performance, so as to supplement the missing nutrients in time and reduce the loss. Some common symptoms of element deficiency are listed below.

⑴ nitrogen deficiency

Under the condition of nitrogen deficiency, the leaves become light green or yellow-white, the branches are thin and weak, and the new leaves on top shoots become smaller gradually, and at the same time, they are easy to fall.

The main symptoms are that the new branches are thin and short, the leaves are small and erect, the leaves are gray-green, the petioles, leaf veins and cortex turn red, the flowers and fruits are small, the fruits are precocious and easy to fall off, the fine roots are many, the big roots are few, the new roots are yellow, and the ability to resist diseases and insect pests and drought is weakened.

Take soybean as a row, lack of nitrogen fertilizer in the growth period, starting from the lower leaves, the leaves become light green, and then gradually turn yellow and withered, and sometimes bronze markings appear on the leaves. In severe cases, the plant stops growing and the leaves gradually fall off.

⑵ phosphorus deficiency

Insufficient phosphate fertilizer will hinder the formation of crop flower buds, make crop flowers small and small, and easily lead to poor fruit development. In the early stage of crop growth, the effect of phosphorus fertilizer is not very obvious, but in the middle and later stage, phosphorus deficiency will affect the effective accumulation of nitrogen and protein synthesis. The symptoms of phosphorus deficiency in different crops are different.

The phosphorus deficiency of wheat was characterized by slow growth of seedlings, poor development of roots, decrease of tillers, purple at the base of stems, dark green leaves, slightly purplish red, few grains per spike, and a significant decrease in 1000-grain weight.

The manifestation of phosphorus deficiency in maize was slow growth in seedling stage, obvious symptoms in 5-leaf stage, purple-red leaves, short and small corn cobs, curved shape, baldness prematurely, and most grains were not full.

The manifestation of phosphorus deficiency in soybean is that the leaves become dark, dark green or dark green, the leaves are small, pointed, narrow, and erect upward, the plants are thin and grow slowly. In severe cases, the stem may appear red, and if the soybean is deficient in phosphorus after flowering, the leaves will appear brown spots.

The performance of phosphorus deficiency of fruit trees is poor fruit quality, slow growth, sparse leaves, yellowish brown leaves, easy to appear early shedding phenomenon.

⑶ potassium deficiency

Lack of potassium nutrition, the stem is slender, in serious cases, the leaf tip and leaf margin are scorched, the leaf is wrinkled, the old leaf edge is curled yellow, burning color and easy to fall off. The main manifestations are that the tip of the lower leaf of the general crop turns yellow, gradually turns yellow along the edge of the leaf, and both sides of the leaf vein and leaf midrib are still green.

In severe cases, most of the leaves are withered and yellow, and the edges of the leaves are burning; cereal crops show weak tillering ability, soft stems, and easy lodging; dicotyledons leaves curl, gradually wrinkle, sometimes leaves are incomplete, but the middle of the leaves remain green; the quality of root crops is reduced, the quality is poor, the fruit ripening period is inconsistent, the pulp is woody, and the taste is sour and bitter.

Magnesium deficiency in ⑷

Magnesium deficiency first yellowed between the veins of the old leaves, and gradually spread to the upper new leaves, the mesophyll was yellow but the veins were still green, and various color spots appeared between the veins.

⑸ iron deficiency

The symptoms of iron deficiency are similar to those of magnesium deficiency, except that iron deficiency first appears yellowing between the veins of the new leaves, and the veins are still green, and then the whole leaf turns yellow or whitish.

⑹ manganese deficiency

The symptoms of manganese deficiency were basically similar to those of iron deficiency. Chlorosis spots appeared between leaf veins and stripes were gradually formed, but leaf veins were still green.

Boron deficiency in ⑺

The young leaves of boron deficiency lost chlorosis, the leaves were thickened and wrinkled, the leaf margin curled upward, the root system was underdeveloped, the terminal bud and young root growth point died, flowers and fruits fell.

⑻ calcium deficiency

The terminal bud of calcium deficiency was damaged, and caused root tip necrosis, green leaf loss, leaf edge curling up and scorched, leaf tip often hooked.

⑼ sulfur deficiency

The sulfur-deficient leaves become light green, even white, expand to new leaves, the leaves are slender, the plants are short, the flowering is delayed, and the roots are obviously elongated.

⑽ zinc deficiency

The internodes of zinc deficient plants were obviously atrophied and ossified, the leaves became yellow or smaller, macula appeared between the veins, spread to new leaves, and the young leaves were hard and small, and yellowing.

⑾ molybdenum deficiency

The young leaves of molybdenum deficiency are yellowish green, and the leaves lose green and wither, which is easy to cause necrosis.

⑿ copper deficiency

The tips of copper-deficient leaves were white, the young leaves shrunk, and white leaf spots appeared.

two。 Common misunderstandings in fertilizer application at present

⑴ organic fertilizer drying

Human manure and chicken manure have become the main base fertilizer for vegetable production in greenhouse, but vegetable farmers often dry human manure and chicken manure in the field for convenience. This practice will cause maggots to reproduce, nitrogen volatilization and loss of nitrogen nutrients in fertilizers.

⑵ calcium, magnesium and phosphorus as base fertilizer in alkaline soil

Calcium magnesium phosphorus is a weakly acidic fertilizer insoluble in water and can be gradually transformed into water-soluble phosphate absorbed by crop roots under weak acid conditions and applied in alkaline soil; it can not solve the urgent need of crop seedlings for phosphorus resulting in physiological phosphorus deficiency.

Application of ⑶ superphosphate as topdressing on the ground

The movement of phosphorus in the soil is small, generally at the point of 0.5 cm, and the moving range is between 1 cm and 3 cm. Therefore, surface application is difficult to reach the crop rhizosphere, so it can not supplement the role of phosphorus in crops.

Watering immediately after ⑷ urea application

Urea is an acylamine nitrogen fertilizer, which is soluble in water, and can be transformed into ammonium bicarbonate after being decomposed into soil, which can be absorbed by crops and watered immediately after surface application, which is easy to make urea lose with water and reduce fertilizer efficiency.

⑸ ammonium bicarbonate sprinkled with water

This method often results in a lot of fertilizer at the inlet, crop growth varies, and it is difficult to manage, while the greenhouse temperature rises in the afternoon, ammonia escapes from the soil, fumigating the lower leaves of crops, resulting in fertilizer damage.

3. The main methods to improve fertilizer efficiency

Compost and compost of ⑴ organic manure as base fertilizer

In late July, 4000 kg of human dung, 100kg of calcium, magnesium and phosphorus and 400kg of chopped wheat straw (bran) were added in the sunny place, and then piled into a bun shape, covered with dilapidated plastic film or strictly piled with straw mud for 30 days, that is, high-quality organic fertilizer was used as base fertilizer in the greenhouse.

Concentrated application of ⑵ superphosphate as base fertilizer

Open a deep trench of 8 cm in the transplanting row, cover the soil with 5cm after the removal of phosphate fertilizer, and then transplant crops in a shallow ditch to shorten the distance between phosphate fertilizer and crop roots to make up for the weakness of low phosphorus mobility.

Early, deep and extra-root application of ⑶ urea

According to the fertilizer and water demand of crop development stage, topdressing and deep application were applied in advance, which increased the utilization rate by 28% compared with shallow application. The greenhouse temperature is 7 days earlier when the greenhouse temperature is 15 ℃ 20 ℃, and 5 days earlier when the greenhouse temperature is 20 ℃. After topdressing, the soil is tightly covered, and the deep hole application can be used for the crops with large row spacing.

According to the temperature of the greenhouse, it was watered every 7 days to make it fully ammoniated in the soil to facilitate the absorption and utilization of crops. During the crop growth period, 0.3% urea solution can be used to spray leaves, once every 7 days, 100 kg solution per mu for 3 times in a row.

⑷ ammonium bicarbonate deep application

Ammonium bicarbonate is an ideal quick-acting fertilizer for vegetable topdressing in warm winter greenhouse. Because it is rarely volatilized at 20 ℃, ammonium bicarbonate can be dissociated into ammonium ions absorbed by soil and then slowly released for crop root absorption. Even under the soil temperature of 5 ℃, ammonium bicarbonate can be transformed and decomposed and absorbed by crops.

When topdressing, a deep trench of 10 cm is opened 10 cm away from the crop rhizome, and the soil is strictly covered after spraying fertilizer, which can increase the utilization rate by 10%, increase the yield by 10% compared with shallow application, and increase by 7.8% compared with water application.