Detailed Explanation of Sprinkler Irrigation Techniques for Soybeans During the Pod-Filling Stage
When soybeans enter the pod-filling and maturation stages, they still need some water and nutrients to promote material accumulation and maturation, improve the seed-setting rate, and increase yield. For many years, when soybeans enter the pod-filling stage, conditions are generally very dry, which adversely affects the pod filling and maturation of the top and upper pods. In response, some farmers use sprinkler irrigation with well water during this period to alleviate the drought.
Production practice has proven that soybeans sprinkler-irrigated with pumped water during the pod-filling stage not only fail to promote maturation after one week, but instead cause some branches and plants to turn yellow prematurely or even die, thereby reducing yield.
The reason is that after pod filling, soybeans enter the maturation stage. Because the root system has aged, humidity is high after sprinkling, and soil temperature drops, the root's transport function is inhibited and reduced, accelerating the aging process and decline of the soybean root system and causing partial loss of transport function. At the same time, when humidity is correspondingly too high, the roots are also prone to soybean root rot, causing the entire plant to dry up and die, and further causing death due to improper sprinkler irrigation.
If sprinkler irrigation is done properly, the desired effect can be achieved. The following points should be noted for sprinkler irrigation of soybeans in the later stage:
1. Sprinkler irrigation should be carried out before pod filling. At this time, the soybean root system has not fully entered the aging stage and has strong resistance to low temperature, humidity, and disease. After sprinkling, it is not only very beneficial to soybean pod filling and rapid maturation, but also less likely to cause root rot and other problems. Soybeans sprinkler-irrigated during this period have full grains and a large yield increase, making it a critical period for increasing soybean yield.
2. The timing of sprinkler irrigation should be chosen. If the weather temperature is high, sprinkler irrigation should avoid high temperatures (except river water), and sprinkling should be chosen in the early morning or evening to reduce the temperature difference between the soybeans and the well water.
3. In later-stage sprinkler irrigation, the irrigation time should be reduced or shortened to minimise high soil humidity. When sprinkler-irrigating in the late pod-filling stage of soybeans, even more attention should be paid to soil temperature and humidity when pumping well water, so as to avoid causing soybean root rot. When the temperature is high, sprinkler irrigation should stop once it connects with the humidity in the soil, and violent sprinkling should not be used. When the temperature is relatively low, the sprinkler irrigation intensity should be less than the soil infiltration rate, and it is advisable that no runoff or standing water is produced on the surface, so as to meet the needs of soybean pod filling.
4. Sprinkler irrigation and fertilisation should be carried out simultaneously. For soybeans sprinkler-irrigated in the later stage, foliar fertiliser should be sprayed on the crop 1—2 times in a timely manner to quickly promote pod filling and maturation. For each hectare of soybeans, 7.5—10 kg of urea or 1.2 kg of monopotassium phosphate can be used for manual foliar spraying, to supplement the nutrients that the crop cannot provide in time due to root aging, and at the same time it can also promote and improve the crop's leaf function, prolong vitality, and improve photosynthetic efficiency, thereby increasing the seed-setting rate and yield.