At present, the main soil treatment agents for corn and soybean fields in our province are acetochlor, which also uses isopropylamine and metolachlor. They are all budsides, and the application time must be consistent with the germination period of weeds. Play a weeding effect. Gramineous weeds are mainly absorbed by the coleoptile and broad-leaved weeds are absorbed by the hypocotyls. This kind of germicide can only effectively kill the grassy weeds and cotyledons that have been exposed to the surface of the coleoptile and have not been arched (or indeed Leaf) Some broad-leaved grasses that have not been excavated have only an inhibitory effect on one-leaf and one-hearted grass weeds, and basically have no effect after two-leaf and one-heart period. There are several situations that lead to the late spraying period: 1. The application of rain, etc., causes the application of pesticides to be late: In the spring drought year, all soil treatment agents have poor efficacy. Only after the application of appropriate rainfall (>10mm) or good ploughing, or irrigation (such as sprinkling irrigation) after spraying, the pesticide can be infiltrated into the shallow plough layer to kill the germinating weeds. It is necessary to correctly grasp the application period to make it coincide with the germination period of weeds. When the rain is applied over the germination period of weeds, the efficacy is certainly not good. The corn, soybeans and other crops planted immediately after planting in our province should generally be applied 7 days after sowing. In late sowing fields, due to the increase in temperature, weeds sprout quickly and they can't wait for rain. 2, spring warmer early, the temperature is high, the phenology period ahead of time, weeds early sprouting. It is easy to miss the sprouting period of weeds during the application period. The spring warmer early, the weeds germinate ahead of time, and the crop sowing period did not advance accordingly, many places in the broadcast 7-10 days after spraying, the longest waited 21 days. After waiting for the rain and other problems, some of the weeds had been excavated or unearthed during the application, and weeds were missing. 3, autumn soil preparation, autumn for the ridge area easy to apply late, when the sowing of the shallow plow layer due to high temperature, weeds have been in a germinating state. In the case of barnyardgrass, the seeds germinate at 10Â°C, and the optimum temperature is 20-30Â°C. The first seeds that germinate and cause grass damage are 1-2cm grass seeds (grass). The lower the seed germination rate, the lower the seed germination rate. Even if it does not germinate, the current dry field is not deep-turned. Rotational ploughing is often used, resulting in grass seed mostly in shallow plough layers, and individual even unearthed. Where autumn and autumn land preparation, autumn ridge, must be applied as soon as possible after sowing, do not wait too much rain and so on. If the spring preparations are delayed and sowing is not done, the pesticide should be applied in time after sowing. It is not appropriate to sow out too late weeds for most of them to be unearthed and then use acetochlor instead. 4. It is of utmost importance to improve the quality of soil preparation (without large blocks and straws) before resuming sowing, especially after sowing. Herbicides do not exert their effects on water, and water is the carrier through which herbicides migrate to the plough layer. In non-repressed, droughty soil layers, herbicides are either strongly adsorbed by fine soil particles or are stripped by the wind. The same soil quality, sowing date, application amount and closed time, timely repression and re-application of pesticides after sowing were closed, and the weeding effect was much better than non-repression. The repression must be carried out with heavy rolling to achieve a soil compaction of 1.2-1.3 g/cm3, which is very favorable for the protection of crops, the emergence of crops and the improvement of weed control. Acetochlor is relatively sensitive to soybeans and it is not desirable to wait for rain application. Soybean arch season in the case of low-temperature rainfall, can inhibit the growth, acetochlor and sophosulfuron in the vicinity of the soybean near the arch period, the phytotoxicity is obvious, or even out of production. The absorption of weeds through the roots of weeds in the weeds basically does not affect the weeds. The application period is wider, and the unearthed 2-leaf weeds can still be killed. The period of application of E-and-Dua mixture should be based on acetochlor and DÃ¼rr.