Cotton narrow row spacing should be widened: The second in a series of recommendations from rural advisory services in 2008
Before sowing, the author visited and investigated some cotton regions in Hebei, Shandong, Shanxi and Shaanxi. In most areas the cotton narrow row spacing is too narrow, seriously hindering the normal growth and development of cotton plants, and a planting reform of the population structure is essential. The pressing task is to widen the narrow row spacing.
In order to carry out plastic film mulching of cotton, cotton farmers mostly adopt wide-and-narrow row sowing, sowing two rows at once. Most areas use 90 cm wide plastic film, with the narrow row spacing about 45 cm wide. This is not conducive to the normal extension of fruiting branches and flowering and boll setting, and also causes unbalanced growth on both sides of the cotton root system. Many cotton farmers have experienced this: when picking cotton, the wide-row side yields far more than the narrow-row side.
In recent years, cotton farmers in some areas have used 1 m wide plastic film to mulch cotton, which can widen the narrow row spacing to about 55 cm. This not only benefits the growth and development of the fruiting branches and root systems on both sides of the cotton plant, but also allows 1 to 2 cultivations between the narrow rows after the film is removed in mid-June, which helps soil aeration, moisture conservation and the downward growth of the cotton root system.
Not long ago, during a rural service visit to Ruicheng County, Shanxi, the author learned that local cotton planting generally uses 80 cm wide plastic film to mulch cotton, with a narrow row spacing of only about 35 cm. This not only causes extremely unbalanced growth and development on both sides of the cotton plant, but also causes the narrow rows to close over too early. If the density is also too high and the leaf branches are not removed, it will inevitably cause the "disastrous" consequences of massive shedding of squares and bolls and few and small bolls. According to cotton farmers in Xi'nan Village, Donglu Township, Ruicheng County, the cotton they planted on the Yellow River beach in 2007 had a large-area yield of only 250 to 300 jin per mu, which is directly related to the too-narrow narrow row spacing, the rather high density and the failure to remove leaf branches. One cotton farmer, because too few seeds fell from one seed drill hole at sowing, ended up with only one row of the two rows having a full stand while the other row had many missing plants, yet in the end the yield was over 400 jin per mu, which was nevertheless relatively high for the local Yellow River beach. Therefore, 1 m wide plastic film should be used instead, and the narrow row spacing must be resolutely widened to more than 50 cm. If Ruicheng County does not carry out the planting reform of widening the narrow row spacing, it will be difficult for cotton yield to improve.
Whether to adopt equal row spacing planting cannot be generalized; it must depend on soil fertility, irrigation conditions and the yield-increasing potential of the variety. Where irrigation cannot be guaranteed and soil fertility is low, equal row spacing planting is not suitable, and still less is it suitable to blindly adopt 1 m wide row spacing. This is because 1 m equal row spacing makes it very difficult to ensure a density of more than 2000 plants per mu, and in drought it easily results in a low leaf area index and large gaps between rows, failing to make full use of land and light, air and heat resources, thus leading to losses. For general soil fertility, irrigated conditions and conventional varieties, under full-season chemical regulation, the equal row spacing in northern cotton regions should preferably be 80 cm, with a plant spacing of 1 chi and 2500 plants per mu. If the row spacing is narrowed further, it will bring difficulties to sowing and film mulching, and it is better to adopt wide-and-narrow row planting, which is more convenient for operations.