What is the highest salinity of water in cotton planting?

I am from Xinjiang. At the end of last year, I wrote something to meet the requirements of my superiors and see if I could help the landlord.

Xinjiang has a long illumination time and a large temperature difference between day and night, showing a typical temperate continental climate. Due to the uneven terrain and large evaporation in the arid desert area of Xinjiang, and the high groundwater level in Xinjiang, groundwater rises to the ground along the capillary, resulting in the continuous accumulation of salt in the soil.

Generally speaking, when the soil salt content is below 0.3%, cotton can emerge normally; When the soil salt content is 0.3-0.5%, cotton can barely emerge, but the cotton seedlings are weak; When the soil salt content exceeds 0.5%, it is difficult for cotton to emerge and grow.

1 Effect of Saline-alkali Land on Cotton Growth

I even have a part of saline-alkali land, which has a great influence on the growth of cotton every year because of its high salt content, mainly in the following points:

1. 1 The strip field with serious saline-alkali soil and high groundwater level make the sowing date later than that of normal cotton field.

1.2 During sowing, a layer of dry and virtual soil is easily formed on the soil surface. If the seeds are only planted on this dry virtual soil, it is difficult to sprout, and water must be replenished.

1.3 The soil moisture in saline-alkali land is easy to make people misjudge the soil moisture, which leads to the difficulty in checking the soil moisture before sowing and replenishing water after sowing.

1.4 After the temperature warms up, the saline-alkali soil is cool, and the ground temperature rises slowly, which makes the cotton seedlings emerge slowly, and after the emergence, the seedlings are weak, the growth potential is not strong, and even the seedlings die. Especially in the drilling field with water supply, if there is too much water supply, the seeds are easy to sink, and the cotton seedlings can't be pushed out after the alkaline soil on it meets the water to form a plate, which leads to rotten seeds. If you encounter cold weather, the situation is even worse.

1.5 Different parts of the strip field in saline-alkali land have different salt content and different growth conditions of cotton seedlings, which leads to the phenomenon of "four generations living under one roof" in one field and "planting seedlings in the east and planting seedlings in the west" in the same field.

2 methods to improve saline-alkali land

2. 1 Dig the alkali drainage channel, do a good job of dredging the alkali drainage channel, and reduce the groundwater level.

2.2 Due to the serious alkalization of saline-alkali land in spring and autumn, the usual practice in the past was irrigation and ploughing after spring. In the past two years, many contractors for planting saline-alkali land have actively explored new methods and achieved some results. The first method is to plow the land in autumn, irrigate it in the next spring, and then turn it shallow after spring irrigation, so the effect of pressing alkali is better than that of spring irrigation and spring tillage alone; The second method is to plough the land in autumn, and irrigate it directly in micropores and sow it wet after spring. The second method seems to have gained a lot of recognition in the company in the past two years, because it can be broadcast 15-30 days in advance. As long as the emerging water is well watered, the rising speed of ground temperature will be much faster than that in the field where soil moisture is maintained, so that cotton seedlings will grow better. Micro-hole irrigation is very effective in removing alkali from soil under film, so that cotton seedlings can grow in a better environment. The disadvantage of this method is that the cost per mu of micro-hole irrigation is about 200 yuan higher than that of flood irrigation, so it is necessary to increase the yield per mu by 40-50kg in normal years to offset the increased cost of micro-hole irrigation. In saline-alkali land, the income is not high and the contractor's funds are limited, so our workers need to bear certain risks. Without large-scale irrigation, it is easy to cause secondary salinization of soil.

2.3 Improve the quality of soil preparation before sowing, reach the six-character standard of "neat, flat, moist, broken, loose and clean", prevent the accumulation of salt and alkali, and control the height difference of farmland below 5cm. After sowing, actively and timely intertillage to improve the ground temperature.

2.4 After cotton seedlings come out, the method of promoting control should be adopted to make cotton seedlings grow evenly and facilitate management. The topping time of cotton field in saline-alkali land can be delayed a little compared with that of normal cotton field, but it must be finished before July 15, and the big seedlings and small seedlings should be aborted together, and there should be no psychology of letting the seedlings grow because they are small.

2.5 through fertilization to change the nature of the soil and cultivate fertility. Saline-alkali soil has low nutrient content. By applying more organic fertilizer, fermented garbage and fly ash, using organic acid to buffer saline-alkali, improving soil aggregate structure, adjusting soil water, gas and heat conditions, improving soil permeability, and improving soil fertility and water retention capacity. Apply more acid fertilizers such as potassium sulfate and zinc sulfate to neutralize soil alkalinity. In addition, it is also a good method to use soil improvers such as "Hekang" and "Saline-Alkali Abundance".