A recent article in the Delta Farm Press on early irrigations that may have saved some soybean fields was absolutely on target. I realize no one wants to think about irrigating prior to July 4, but to attain maximum yield you must meet the crop's needs season-long.

From time to time I hear that there is no benefit to irrigating prior to bloom. Personally, I hope this growing season has put that comment to bed. Some years that is true, but you must focus on the crop's stage of growth and needs, not the time of the year.

We had a lot of short beans this year due to a long cool, dry period in May. If you could irrigate and failed to do so, you kept plants from achieving maximum growth and possibly impacted the crop's yield potential.

The dry weather we experienced in May and June closely simulated 1983, the only difference being that it occurred earlier in the year.

Only about 30 percent of our soybean crop can be irrigated, but for those who could water, it was a much-needed input.

In our statewide verification program, we encouraged all participating growers who could to irrigate. Weeks later it became obvious that paid off because we began observing plant death statewide. Plants that died were stressed and aborted their root systems.

Plant death started showing up soon after it started raining in June. When that happened, many took the stance that plants were stressed from watering and that watering again once it dried was not the right move.

This was far from accurate. Plants stressed the greatest died; stress plants again and additional plants will die. Many plants were stressed earlier, but when stressed again, they continued the earlier trend.

I will admit that irrigation needs hit early this year, but because the crop was early, it reached peak demand earlier.

If you are planting early, the needs of the crop will occur earlier. If you fail to provide these inputs the crop may survive but it will give up its earliness; this translates into reduced yield.

To avoid some of the problems with irrigation, consider irrigating on a slightly earlier schedule. If you just keep waiting and waiting, plants are being stressed. Watering stressed plants magnifies the problem.

Many say watering scalds plants. It will not if you water on time and get through timely. Slow watering, large sets, and small holes all cause watering to take longer. If you are experiencing these problems, turn irrigation on sooner. If you turn on a little too quick, it will just water through faster, not as deep, which will avoid problems if it rains soon after watering. Use smaller sets and large holes, gates or multiple holes to water faster.

The symptomology observed earlier in the year from plants dying was similar to SDS, stem canker, and red crown rot. Although leaf symptomology is similar it is imperative that if you observe a problem you get it positively identified. Do not guess. Identifying problems correctly is needed in order to correct the problem and avoid future concerns.


Alan Blaine is the Mississippi Extension soybean specialist. e-mail: ablaine@pss.msstate.edu