Spring of 2007 proves to be unusual
Brian Rees
Saturday, May 19, 2007
This has been an extremely unusual and trying spring in 2007. What has started off and looked good has become a lot less appealing. And some things are yet to start.
As I travel across the county I have noticed a few fields of good-looking corn, but many fields of corn just don’t quite look right. There have been some fields with corn that is purple to brown, and some fields that have problems related to the heavy rains within the past two weeks. It would probably be a good idea to take a look and see what the issue is and if there is anything you can do about it.
Most of the purpling and browning of the plant leaves is the result of a phosphorus deficiency in the plant. The recent wet spell and cool temperatures combined with sunshine after the warmer temperatures earlier in the spring has caused the young corn plants to be unable to convert the sugars produced during the day to starch and move them where needed. The plant responds with pigment production that affects the leaves.
Cooler soil temperatures and soil compaction reduce the uptake of phosphorus by the plant. Phosphorus plays a key role in the ability of plants to metabolize nutrients. Warmer weather and sunshine will enable the roots to take up an adequate amount of phosphorus and metabolize the nutrients trapped in the leaves, and should let the plants develop normally for the remainder of the season.
Another issue is alfalfa. Alfalfa is recovering extremely slowly from freeze injury this spring. The crop basically had to start from scratch in mid-April and regrow from severe freeze injury and alfalfa weevil infestations. This damage delayed the production of new carbohydrates within the leaf tissue, and further depleted food reserves in the roots just when these reserves should begin to accumulate.
As a result of the combination of freeze injury, early-season insect damage, saturated soils, and diseases, much Lyon County alfalfa is in a rather fragile condition. Food reserves are depleted and in some cases, there has been irreversible damage from crown rot or freeze injury.
Stands less than 12-15 inches tall in weakened condition should not be cut until the plants have recovered well enough to have started producing carbohydrates and replenishing root reserves. It will be tough to do, but the best management strategy where stands are short is to leave the crop alone. It would do more harm than good to mow the fields at this point, since that would deplete needed food reserves in the roots even more.
On the other hand, if the plants are taller than about 15 inches, or knee-high, it’s probably best to cut the stand soon before leaf diseases become too bad. In this situation, there has probably been enough time for the leaves to replenish at least some of the food reserves in the roots. Producers should expect slow regrowth, however, because of the combination of earlier stresses and low food reserves.