ISSUE 13   July 25, 2002

Growing degree days for wheat range from about 100 ahead of the 30 year average at Wishek to about 140 behind the average at Bowbells. This is probably overly optimistic due to the fact that most wheat was seeded in mid-May, not the end of April. For this reason most of the wheat north of the drought-stricken south-central and southwest areas are weeks away from combining. Also, the growing degree comparisons from May 10 show all areas probably a week ahead of the average, but when the late corn planting around Memorial Day is factored in, we are probably near to slightly behind normal for this time of year.

 Dave Franzen
NDSU Extension Soil Specialist
(701) 231-8884
dfranzen@ndsuext.nodak.edu

There has been a rash of interest lately in foliar fertilizer for soybeans. Some of this interest has to do with a high yield soybean farmer from the state of Michigan who happens to use foliar fertilizer in his program. Some of has to do with a magazine article last year about a "study" in Minnesota by a private firm with positive results. The last big hype regarding foliar fertilization happened my first year in the fertilizer retail business in 1976. A study from Iowa State reported a huge (about 17 bushels) increase in soybean yield with three application of a N-P-K-S liquid foliar fertilizer. Everyone was awed at the results and everyone made haste to the phone to order this formula fertilizer. My company had about twelve locations where we split fields and applied the product. Of the hundreds of field and research tests made that year and next year across the corn belt very few could see positive results. In fact, when the Iowa State data were finally published in a refereed journal, we learned that the big difference reported in the news was the only site with a big difference in a study with several sites; the others with little or no difference in yield. A recent study at Iowa State was conducted at 27 sites, applying an N-P-K fertilizer at the 5-leaf stage to soybeans. Only three of the sites showed positive yield responses and another two sites showed yield decreases. A study in South Dakota a couple years ago showed no yield increases to broadcast 28% on mid-season soybeans with rates from 10-50 lb N/acre. Yield decreases were shown at rates generally above 30 lb N/acre (10 gal/acre). My read from all of the experiments with foliar N applications is that if the leaves are green and N is not evidently deficient, the chances of success are so slim that if a grower is applying a foliar treatment to all fields he will be losing money most of the time.

The only time that I would recommend N application mid-season on soybeans is if the soybeans are N deficient. From recent phone calls, it is evident that a few fields, mostly first-year soybean fields, have poor nodulation and are noticeably yellow (not chlorotic-in iron chlorosis the veins usually remain green. In N deficiency, veins are commonly yellow to pale green also). These fields have a good chance of yield increases (a Kansas study following heavy rains and significant denitrification showed this) if the nitrogen is applied with little burn and rainfall washes the fertilizer into the soil sometime within 48 hours of application. Rowed beans could be side-dressed similar to any row crop. My top choice for solid-seeded soybeans would be 28% N using streamer-bars. My next choice, but one generally harder to apply and riskier in volatility losses would be broadcast urea. My last desperation choice would be broadcast 28%, not higher rates than 10 gal/acre (30 lb N/acre) and expect some spectacular burning. You will meet neighbors you haven’t seen in 30 years a couple days after application. I think I would rather buy some streamer bars. Rates to use would be about 50 lb N/acre.

Dave Franzen
NDSU Extension Soil Specialist
(701) 231-8884
dfranzen@ndsuext.nodak.edu

This summer, some fields of sugarbeets appear unusually yellow for mid-July. Supplemental N fertilization at cultivation for sugarbeets should be approached carefully. Soil tests and petiole sampling should be conducted, with the soil sampling depth at 0-2 feet. If soil tests come back below 50 lb/acre in the top 2 feet (generally soil tests under truly N deficient beets will only run about 20 lb/acre) and petiole tests are well below 10,000 ppm, then some supplemental N may be justified. Rates of up to 30 lb/acre N should be adequate to take the beets through the rest of the season. Yellowing may also be caused by plant reaction to excess water or the beginnings of Rhizomania. Too much N will decrease sugar content and grower profits.

Dave Franzen
NDSU Extension Soil Specialist
(701) 231-8884
dfranzen@ndsuext.nodak.edu