Cultivation techniques of spinach

The growth process of spinach can be divided into two stages:

1. Vegetative growth period: from unearthed cotyledons to inflorescence differentiation. The initial temperature of seed germination was 4 ℃, and the optimum temperature was 15-20 ℃. When the temperature was too high, the germination rate decreased and the germination time prolonged. The cotyledons expand to the appearance of two true leaves and grow slowly. After the expansion of the two true leaves, the leaf number, leaf weight and leaf area increased rapidly. When the daily average temperature was below 23 ℃, the rate of leaf primordium differentiation at the seedling tip slowed down with the decrease of temperature. The leaf growth is the fastest when the daily average temperature is 20-25 ℃. After the inflorescence primordium was differentiated at the tip of the seedling, the number of basal leaves did not increase. The number of leaves during inflorescence differentiation varied with sowing date, ranging from 6-7 to more than 20.

2. Reproductive growth period: inflorescence differentiation to seed maturity. Spinach is a typical long-day crop, which can differentiate flower buds in a wide range of temperatures under long-day conditions. Spinach sown in summer can still differentiate flower buds even if the low temperature is less than 15 ℃. The days of inflorescence differentiation to bolting varied greatly with different sowing dates, ranging from 8-9 days to more than 140 days in the elderly. The length of this period is related to the harvest time, the length and the yield. Spinach has strong cold tolerance, and the areas where the average lowest temperature in winter is about-10 ℃ can survive the winter safely in the open field. Varieties with strong cold tolerance, plants with 4-6 true leaves, can withstand short-term low temperature of-30 ℃.

> cultivation techniques: spinach does not have strict requirements on soil, and its cultivation is early in sandy loam, so it is easy to get high yield in clayey loam. The acid resistance is weak, the suitable soil pH value is 5.5-7, and the soil pH grows poorly when the soil pH value is below 5.5 or above 8. The main cultivation stubble: early spring sowing, late spring harvest, called spring spinach; summer sowing and autumn harvest, called autumn spinach; autumn sowing next spring harvest, called overwintering spinach; late spring sowing and summer harvest, summer spinach. For direct seeding, when sowing in early spring and summer, in order to ensure the whole seedling, the seeds were soaked in 15-20 ℃ for one day, germinated and sowed wet. Generally, the sowing rate is 3-3.5kg per mu. The sowing amount of overwintering spinach is large, more than 4-10 kg per mu. Flat beds are mostly used in the north of China, while high border cultivation, sowing or strip sowing are mostly used in the south. Quick-acting nitrogen fertilizer was applied 1-2 times after two true leaves. The absorption ratio of nitrogen, phosphorus and potassium in spinach was 2%. Excessive application of nitrate fertilizer would increase the content of nitrate. The soil moisture should be kept 70-80% of the field capacity during the whole growth period.

In order to prevent spinach from overwintering, it is necessary to protect against cold and preserve soil moisture. Measures such as setting up wind barriers, irrigating "frozen water" and covering barnyard manure were taken in northern China before soil freezing. In order to ensure the whole seedling and promote the growth of summer spinach, sheltering is often used in the Yangtze River Basin and South China to reduce the harm of high temperature and rainstorm.

The sowing date of spinach for keeping seeds is a little later than that of overwintering spinach. Strip broadcast, line spacing 20-23cm. After turning green in spring, the miscellaneous plants and early bolting male plants were pulled out one after another, and some nutritious male plants were left, so that the plant distance reached about 20cm. During the bolting period, it is not suitable to irrigate more water, so as to avoid weak lodging of flower bolts and reduce seed yield. After flowering, topdressing, irrigation, foliar spraying 1-2% calcium superphosphate to make the seeds full. After the female plant sets seeds, the male plant is pulled out to facilitate ventilation and light transmission. Most of the stems and leaves are withered and yellow, and the seeds are harvested when they are ripe and threshed several days after ripening.