Key Technical Points for Spring Soybean Sowing in a Year of Severe Drought in Northeast China

Current drought situation in Northeast China and technical guidance for spring soybean sowing:

I. Precipitation and temperature conditions last winter and this spring

In the autumn and winter of last year, the drought in Northeast China was severe, precipitation was lower than normal, and soil moisture was insufficient. From January to October 2007, the average precipitation in Heilongjiang Province was 402 mm, 20% less than the same period in previous years. In addition, this year's widespread "dry sealing of the soil" at the onset of winter was not conducive to soil moisture conservation. Since the beginning of winter, precipitation in southern Qiqihar, most of Daqing, the Hegang area, and some counties and cities in Jiamusi has been more than 90% less than the same period in previous years; other areas have had 10% to 90% less. In January 2008, the average precipitation across Heilongjiang Province was only 0.1 mm, 97% less than the same period in previous years, with most of the Songnen Plain and the western Sanjiang Plain receiving no precipitation at all for the entire month. After entering February, precipitation in various places continued to remain low. Snow depth across Heilongjiang Province also dropped significantly. Compared with the same period in previous years, snow depth in most areas of the province was about 25 cm less. In 2008, the area of cultivated land affected by drought before sowing in Heilongjiang Province may reach 50 million mu. In addition, the continuous warm winter was extremely favorable for soybean pathogens and pest eggs to survive the winter safely, and soybean diseases and insect pests may occur more heavily this year. The spring drought situation in Inner Mongolia is similar to that in western Heilongjiang Province.

The overall meteorological situation in Jilin Province last winter and this spring was slightly higher temperatures and less precipitation. Among these, in October last year, the temperature was 0.6°C higher than the same period in previous years, and precipitation was 20.7 mm, 29% less than the same period in previous years; in November, the temperature was 0.6°C higher than the same period in previous years, and precipitation was 9.3 mm, 39% less than the same period in previous years; in December, the temperature was 2.9°C higher than the same period in previous years, and precipitation was 8.7 mm, 24% more than the same period in previous years; in January this year, the temperature was 0.9°C lower than the same period in previous years, and precipitation was only 0.4 mm, 92% less than the same period in previous years, with precipitation in the eastern region 76% to 98% less than the same period in previous years, and basically no precipitation in the central and western regions; in early February, the temperature was 0.7°C higher than the same period in previous years, in mid-February the temperature was 0.5°C lower than the same period in previous years, and there was no precipitation in early and mid-February, 100% less than the same period in previous years. It is expected that in the spring of 2008, precipitation in most areas of Jilin Province will be lower than normal, and there is a high possibility of low-rainfall drought, especially in the central and western regions. Since the beginning of winter in Liaoning Province, the average precipitation has been only 34 mm, 20% less than the same period in previous years. In particular, since midwinter (January 11), only Huanren, Kuandian, Donggang, and Lushun have had 1 to 3 mm of precipitation, while the rest of the region has had no precipitation, and the provincial average precipitation has been more than 90% less than the same period in previous years. Based on the prediction that the overall trend of precipitation this spring will be slightly lower than normal, there is a relatively high possibility of spring drought this year in most of western Liaoning, southern Dalian, and northern Shenyang, which will affect spring sowing work.

II. Soybean seed supply and preparation

In the spring of 2008, soybean prices reached a historic high, planting benefits improved significantly, soybean production showed a good development momentum, and the planting area will show recovery growth. This year, the soybean planting area in Heilongjiang Province is expected to reach 58 million mu.

Last year, in some areas, due to later drought, the quality of soybean seed reproduction was seriously affected, "stone beans" increased, and the germination rate declined. In addition, because the soybean market in autumn was unclear, seed preparation was clearly insufficient. As the soybean market has recently improved, farmers' willingness to plant has rebounded, resulting in soybean seed supply being unable to meet market demand, and it may be necessary to temporarily transfer seeds from elsewhere or activate national famine reserve seeds. Seeds obtained through normal channels @#@136@#@ are generally of good quality, and purity and germination rate basically meet standards. However, because the quantity of seeds is insufficient, problems of substandard seed quality may occur in individual places, and the quality of farmers' retained seeds is also difficult to guarantee.

III. Technical guidance

In response to the current production situation and the main existing problems, experts put forward the following technical guidance:

(1) Strictly select excellent varieties

Because the climate was dry last autumn, first, the seeds did not mature normally physiologically, and second, mechanical threshing of soybeans increased the possibility of damage to the seed embryo, affecting the germination rate of the seeds. Therefore, seed selection must be strict, preferably by grain selection, removing damaged seeds, and conducting germination tests well. The selected varieties should be of good quality and high yield potential, with strong adaptability, and cross-region planting must be prohibited. Seed transfer should be organized, helping farmers purchase seeds through normal channels and ensuring that purity and germination rate basically meet standards.

(2) Do a good job of seed treatment

First, sun the seeds before sowing. Sunning seeds generally can increase the germination rate by about 13% and advance emergence by 2 to 3 days. Second, chemical seed dressing or seed coating. With low temperature and drought, seeds remain in the soil for a long time and are prone to diseases and insect pests, so soybean seed coating agents can be used at a pesticide-to-seed ratio of 1:75 to 100 for control. To control soybean root rot, 50% carbendazim-thiram mixture at 0.5% of seed weight or 50% carbendazim at 0.3% of seed weight can be used for seed dressing. For plots with severe insect damage, coated seeds containing both fungicides and insecticides should be selected. For uncoated seeds, 35% mephosfolan emulsifiable concentrate should be used for seed dressing to control soil-dwelling pests. Ammonium molybdate can be added to the seed dressing agent to improve soybean emergence rate and nitrogen fixation capacity. In addition, for continuous and alternating cropping fields, attention should be paid to using poisoned bait to control rodent damage after emergence.

(3) Select appropriate sowing methods according to local conditions

For plots without autumn plowing, use no-till sowing on the original ridge; for autumn-plowed and ridged plots, use flat sowing followed by ridging or flat planting with narrow-row dense planting; for plots with poor soil moisture, use deep furrow opening, shallow covering, and heavy compaction; for plots with severe drought, use the sowing method of plastic film mulching between rows, and carry out continuous operations to prevent soil moisture loss.

(4) Adopt "early sowing" technology to make good use of "returning moisture" and strive to preserve full seedlings in one sowing

Sow while there is moisture to preserve full seedlings. We must seize the favorable opportunity of rising ground temperature and use early spring "returning moisture" to sow while there is moisture. Sowing can be carried out when the stable ground temperature in the plow layer passes 5°C, and continuous operations should be carried out to prevent soil moisture loss. The sowing method of deep furrow opening, shallow covering, and heavy compaction can be adopted. Deep furrow opening ensures that seeds are sown on moist soil, covering is uniform, and after compaction it reaches 2 cm, ensuring consistent sowing depth. Compact after sowing to preserve moisture. When soil moisture is suitable, compact 2 to 3 hours after sowing; when soil moisture is poor, compact immediately after sowing; for plots with high soil moisture (water content >25%) or that encounter rain after sowing, compaction should wait until a 2 cm dry soil layer appears on the surface.

(5) Inspect fields and fill gaps with seedlings

After sowing, inspect the fields regularly. Begin checking soil moisture 3 to 5 days after sowing. For plots with severe moisture loss, take corresponding measures to replenish moisture; before emergence, check bud conditions, and for plots with dried buds or spoiled seeds, promptly reseed with water; after emergence, check seedling and insect conditions, and for plots with missing seedlings or broken rows or affected by insect pests, reseed with early-maturing varieties or apply chemical control.

(6) Promote soil testing and formula fertilization

For a long time, many places have applied fertilizer based only on experience, causing an imbalance of soil nutrient elements and resulting in potassium deficiency and trace element deficiency in production. It is necessary, in conjunction with the soil testing and formula fertilization project implemented by the Ministry of Agriculture, to adhere to scientific fertilization and, according to soil test results, apply nitrogen, phosphorus, and potassium fertilizers in a certain proportion. Encourage the application of more farmyard manure, applied in combination with land preparation; chemical fertilizers used as seed fertilizer should be applied deeply 4 to 5 cm below the seed to avoid burning the seeds.

(7) Use non-long-residual herbicides to prevent and control phytotoxicity

Because continuous and alternating soybean cropping is severe, long-residual herbicides are used relatively often in soybean fields, and there are no land records, which has brought great trouble to structural adjustment. Therefore, the use of non-long-residual herbicides is advocated. Long-residual herbicides mainly include imazethapyr, chlorimuron-ethyl, thifensulfuron, flumetsulam, and clomazone.

In 2008, two situations may occur: 1. In the Sanjiang Plain region, the area of sugar beet and potato will expand, and special attention must be paid to the sensitivity of these two crops to long-residual herbicides; generally, 3 to 4 years of interval are required before planting. 2. The soybean area will expand, and the preceding crop is basically corn. If atrazine has been applied in corn fields at 2000 g/ha, planting soybeans may cause phytotoxicity, which should be taken seriously.