Since 1997 popularized hybrid cotton in Funing county, the application coverage of hybrid cotton has increased year by year, and it has been close to 100% since 2007. The popularization and application of hybrid cotton reduces labor input, improves cotton planting efficiency and increases cotton farmers' income. However, in recent years, with the large-scale application of hybrid cotton in production, there have been many problems and shortcomings in actual production, such as too thin planting density, unreasonable fertilization and inadequate chemical regulation. In particular, the cotton planting density has been declining year after year, and even has a downward trend, which has a great impact on the healthy development of cotton industry in our county.
First, the basic situation of cotton density
1. Basic information
Cotton density is one of the important factors of yield formation, which is inextricably linked with natural climate, soil environment and agricultural technology. Before 1997, all cotton varieties in our county were conventional cotton, and the planting density was 42,000-60,000 plants /hm2. In recent years, with the popularization of hybrid cotton, the rise of fertility level and the vigorous promotion of high-efficiency three-dimensional planting, the planting density of cotton production has shown an obvious downward trend. From 2006 to 20 1 1 year, the average planting density of cotton fields in our county was 39,750 plants /hm2, 35,700 plants /hm2, 33 150 plants /hm2, 32,250 plants /hm2 and 3 1200 plants /hm2, respectively.
2. Reasons for the continuous decline of cotton planting density
(1) Planting combination factor
The unreasonable cotton planting combination is the main reason for the decline of cotton density in our county. Cotton farmers generally believe that small row spacing and premature enclosure are the main factors of high density. In large-scale production, the row spacing is too small and the spacing between plants is too large, which leads to the waste of light and heat resources, poor field permeability, high proportion of rotten bolls and heavy shedding in the middle and lower parts, which is not conducive to high yield of cotton.
(2) Input increasing factors
Due to the rapid popularization of hybrid cotton, the demand for improved varieties is also increasing, which leads to the market price of hybrid cotton seeds much higher than that of conventional cotton, with tens or even hundreds of yuan per kilogram, which leads to the decline of planting density, and most cotton farmers are reluctant to buy seeds, which is far from meeting the actual demand for seeds in cotton fields. On the other hand, with the economic and social development, labor costs have risen sharply. At present, the cost of cotton growers in rural areas is around 50 yuan/day. If the field density is reduced, the cotton field management will be reduced, which will directly reduce the labor cost.
(3) Subjective factors of cotton farmers
In the production practice of hybrid cotton, some cotton farmers gradually formed the wrong idea that hybrid cotton does not need pruning. They think that hybrid cotton has many leaves and strong growth potential, forming the planting habit of not pruning, using public branches to increase the population, improving the total effective number of cotton fields, making cotton plants in the field insufficient and reducing the density. On the other hand, with the rapid development of economy, many young and middle-aged cotton farmers go out to work to earn money, resulting in the situation that the old, the weak, the sick and the disabled are engaged in cotton production, which leads to the subjective need to plant large plant varieties to reduce labor consumption in all aspects of cotton production. In addition, at present, under the condition of low planting density, if cotton is in normal or good years, individual cotton will grow vigorously and the field will be more "tolerant", which also caters to the psychology of cotton farmers and leads to their subjective pursuit.
(4) Climate and resource factors
Our county has a mild climate and good humidity conditions, which is conducive to the development of hybrid cotton growth advantages. In addition, in recent years, the introduction of varieties with great growth potential and obvious individual advantages, increasing the input of cotton fertility and optimizing cultivation management are conducive to individual development. In the late climate, high temperature and slow cooling delayed the effective solar terms, prolonged the effective flowering and boll-setting period, increased the total number of individuals, and also led to the decrease of planting density.
Second, the countermeasures
1. Strengthen publicity and guidance
First, from the subjective understanding of cotton. Through multi-channel and multi-directional publicity, the majority of cotton farmers have realized that the low density of cotton fields has brought many adverse effects on cotton production, such as unstable yield and low efficiency, and realized that reasonable arrangement of planting density is the key technology and prerequisite for winning cotton output. At the same time, through experiments and demonstrations, the high-yield film with high photosynthetic efficiency group dynamic structure was established, typical models were shaped, cotton farmers were organized to observe and exchange learning, perceptual knowledge was increased, and cotton farmers were guided to arrange planting density reasonably.
2. Strengthen technical services
In recent years, due to the influence of objective factors, there are many shortcomings in cotton production management in some areas, such as anthracnose, damping-off disease, ineffective prevention and control of wilt and verticillium wilt, substandard three ditches in cotton fields, and no high ridges in cotton fields. In the case of serious diseases or natural disasters, plants will die due to waterlogging, resulting in lower density. Therefore, in the critical period of cotton growth, agricultural technology departments should always walk in the fields to guide cotton farmers, help them to do all aspects of cotton management and reduce the losses caused by waterlogging.
3. Scientifically determine the density
(1) reasonable planting combination
In recent years, with the popularization of insect-resistant hybrid cotton, the incompatibility of planting combinations has appeared, which is mainly manifested in unreasonable plant spacing, too small plant spacing, too large plant spacing, heavy concealment at the lower part and many rotten peaches. Therefore, it is necessary to take the technical route of expanding rows and shrinking plants, improve the ventilation and light-transmitting environment of cotton fields, reduce wide and narrow row planting, expand the planting area of row spacing, and provide favorable space for three-dimensional planting in cotton fields. Production practice has proved that it is reasonable to control the row spacing of general hybrid cotton within 1 10cm and the plant spacing within 35cm.
(2) Pay close attention to the weather
In recent years, disastrous weather often occurs in cotton production season in our county. From 2005 to 20 1 1 these seven years, there were five disaster years, and the cotton output in these five years was obviously lower than normal. Therefore, we should pay close attention to the annual climate forecast of the meteorological department, adjust the planting density appropriately according to the forecast, and increase the planting density appropriately in unfavorable years to maintain the stability of output.
(3) Scientifically determine the density
According to the plant type characteristics of cotton varieties, the suitable planting density is determined. Varieties with large plant type, strong boll per plant and flat branches have lower density, and varieties with small plant type are appropriately larger. But the fiber characteristics of varieties and the sensitivity of fiber quality to density should also be considered. Sensitive varieties must maintain suitable planting density. The planting density of insect-resistant hybrid cotton varieties with large plant type should be kept at about 30,000 plants /hm2, and the planting density of varieties with relatively compact plant type should be kept at 37,500-42,000 plants /hm2. At the same time, plots with good soil fertility and water and fertilizer conditions should be sparsely planted, and plots with poor soil fertility and water and fertilizer conditions should be densely planted. For three-dimensional cotton fields, it is necessary to consider and determine the appropriate planting density as a whole.
4. Supporting cultivation techniques
(1) Select improved varieties and cultivate strong seedlings.
Select excellent varieties such as Xiangzamian No.3 and Zhong Mian No.47 with strong adaptability and great yield-increasing potential. Efforts should be made to realize timely early broadcasting. The best sowing period in our county is from the end of March to the Qingming period. If it can't be broadcast early in time, it will end early after Qingming. Adhere to early cultivation, promote double-film seedling raising, adhere to reasonable hardening of seedlings, and ensure that seedlings do not leave the bed and the film does not leave the bed. The transplanting period of early crops should be in mid-May. Select the weeding microfilm with the width of 90- 100cm, carefully prepare the soil, cover the soil with plastic film, and open a pool on the plastic film for transplanting, with the plant spacing of 23.3-26.7cm. The plastic film transplanting technology can effectively bloom and set the boll peak ahead of time and prolong the full flowering period. Transplanting should be completed at the end of May for the middle and late cropping cotton fields with high cultivation level.
(2) combine fertilizer with fertilizer to set up a shelf.
Fertilization adopts one bottom, two topdressing and one supplement, and the total application of pure nitrogen is 270-300kg/ hm2. Combined with stubble cleaning and ploughing in winter and spring, 30000kg/ hm2 of organic fertilizer was applied to improve soil fertility and increase the number of straw returned from previous crops. When transplanting (or direct seeding), apply base fertilizer, 600-750 kg of special coating fertilizer for cotton per hectare, and apply cotton boll fertilizer twice in late July and late July, and apply pure nitrogen 70 kg/hm2 and 165438 respectively. According to the seedling situation, foliar spray 1% urea solution every 5 days 1 time in the evening. Chemical adjustment should master the principles of early adjustment, light adjustment and diligent adjustment. Before budding, chemical control should be carried out on the flourishing land, and biochemical agents should be sprayed on the leaves of thin seedlings, weak seedlings and diseased seedlings. At the initial bud stage, 1000mL/ hm2 was used to regulate growth, at the full flowering stage, 45g/ hm2+ was used to shape plant type, and 1500mL/ hm2 was used to reduce abscission. 5-7 days after topping, chemical capping with 75g/ hm2 growth promoter can reduce the occurrence of redundant buds and save cleaning labor.
(3) Comprehensive management to reduce losses
Do a good job in winter ploughing frozen soil and spring ploughing with cotton net, pick up sick and disabled plants in the field, and reduce the base of pests and diseases; At seedling stage, the method of spreading poisonous soil was used to control aphids, cutworms, red spiders, blind stinkbug and other pests. For the third and fourth generations of Helicoverpa armigera, it is necessary to strengthen the forecast, unify the prevention and control, do not use insurance drugs, dispense drugs at will and increase the dosage at will, use drugs strictly according to the forecast of pests and diseases, and combine fertilization and chemical adjustment; When the bell fertilizer is topdressing for the first time, do a good job of uncovering the film, loosening the soil and ridging to prevent disasters and prolong the root function. The whole growth period needs pruning twice, the first time when the male branch reaches two true leaves after budding, and the second time after the second application of flower boll fertilizer after the small line is closed.
refer to
[1] Nanjing Agricultural University, Jiangsu Agricultural College, Hubei Agricultural College, Anhui Agricultural College, etc. , crop cultivation, 199 1: 268-270.