Field Updates

Field Updates

August 10, 2007

Del Hemsath, Extension Educator in Dakota, Dixon and Thurston counties: The third cutting is underway in some alfalfa fields. It's a short crop due to the very little rain that's fallen in the area the past two weeks. Soybeans, along with corn, is beginning to show stress from lack of water. Some areas in northern Cedar County are extremely dry and dryland corn will be cut for silage very soon. There has been an explosion of aphids in all areas the past couple of weeks. Weather conditions have been ideal for aphids, which are increasing in numbers. Some fields are being sprayed due to the rapid increase in numbers. Pastures are done producing as most areas are cool season types.

Tom Dorn, Extension educator in Lancaster County: Last week most crops were showing drought symptoms in mid day.

Corn: Most corn is in the early dent to full dent stage. Many people make the mistake of thinking once corn is dented, the yield is made. Corn in the early dent stage needs about 5.5 to 6.5 inches of moisture and full dent corn needs about 2.5 to 3.5 inches to reach physiological maturity (when dry matter accumulation in the kernel stops). Presumably, irrigated fields have more readily available moisture in the profile than dryland fields and will need less additional water to finish out than dryland fields, but unless we get some meaningful rainfall soon, plan to continue irrigating a while longer.

I have been seeing nitrogen deficiency symptoms in many corn fields since before tasseling stage. The lower leaves are fired up to two leaves below the ear in some fields. These fields have significantly smaller ears than fields which did not exhibit nitrogen deficiency symptoms. Presumably, the heavy May rainfall (over 8 inches in Lancaster County) leached part of the carryover and preplant applied nitrate-nitrogen below the root zone. Another possible cause for nitrogen loss in some no-till fields could be ammonia volatilization from surface-applied urea-based fertilizers (46% dry and 28% liquid). If the fertilizer was surface applied to a wet soil under drying conditions, volatilization losses could have been quite significant unless the nitrogen was carried into the soil by at least one-half inch of rainfall or irrigation within a few days after it was applied.

Soybeans: Late Group 2 soybeans have reached growth stage 7 (beginning pod fill in the lower nodes) and Group 3.x soybeans are at stage 6 (rapid pod elongation). Late Group 2 beans will need about 4 inches and Group 3.x beans will need at least 6 inches of moisture to reach maturity without suffering moisture stress. I am seeing extremely low numbers of soybean aphids in nearly every field but these are of no economic concern at present. Second generation bean leaf beetles are feeding on the leaves but have not reached economic treatment levels. I can find whiteflies in most fields, but am not finding bronzing on the leaves so these are more of a curiosity than an economic factor at this point. Finally, I am finding two-spotted spidermites in low numbers in many fields. I ran across one small spot (maybe 0.01 acre) where the mite population had stunted the beans and had caused bronzing to the leaves. This will bear watching.

Ralph Kulm, Extension Educator in Holt and Boyd counties: Scattered rain over the area has helped a few producers, but most of the area has been very dry since mid June. Much of the dryland crops have been lost already as far as grain production. Some producers have already cut corn for silage. Others are making hay from the corn or grazing it. Irrigated crops look very good but pumping costs have been very high. Most producers have pumped continuously the past month except for shutdowns for oil changes. A lot of dryland producers are looking at wheat on wheat this fall. Where disease wasn't a problem, dryland yields as high as 70 bushels an acre have encouraged producers to plant more wheat.

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A field of corn.