ISSUE 16 August 27, 1998
LESSONS LEARNED IN 1998
Each season, there are lessons to be learned from the unique interaction between soil fertility and the environmental conditions of the growing season. In 1998, there were several learning experiences to be gained if we observed crop and soil conditions closely.
Early in the spring, there were several occasions in which soil samples for N were taken in the fall and then followed up by a spring sampling. In some instances, the spring sampling was higher in N than the fall sampling. This was most evident after sugarbeet, but smaller increases were also seen following scabby wheat and some broadleaf crops. The lesson learned is that previous crop, even if it is not a legume may have some effect not seen in our fall soil test, especially if the crop residues are high in N. NDSU has changed its previous crop credits to include green sugarbeet leaves. In the future, perhaps other crop residues under certain conditions will also have to be added to the list.
Because of falling small grain prices and the disease problems of traditional North Dakota crops, soybean acreage has expanded into previously non-traditional areas. New and old growers alike experienced iron chlorosis this spring. The conditions were aggravated by wet, cool conditions and the effects were more severe because soil salinity in many areas have increased due to several years of above-normal precipitation. The lesson learned is that there is work to do by breeders to increase iron chlorosis tolerance, and also by researchers to determine methods to treat soybeans with soil/foliar/seed iron application in a cost-effective manner. Most growers will also be able to recognize iron chlorosis next time it appears.
Another rotational choice, and perhaps maybe one of the brightest spots in North Dakota agricultural production in 1998 is canola. Because of previous Canadian experiences and recent North Dakota research results, sulfur is recommended out-of-hand for canola, which has a special requirement for the nutrient above any seen for any other crop. Producers recognized the problem and most have applied plant available sulfur, so the incidence of sulfur deficiency in the state is low and yields are relatively high. The transition into canola for most producers has therefore been relatively rewarding. Research in 1998 continues to support the use of sulfur on canola. The lesson learned is that sulfur is very important to successful canola production.
Areas high in salinity across the eastern half of the state continue to increase. The above-normal precipitation experienced since 1993 has increased water tables so that salts are wicked to the surface. Many areas which have lost acres to flooding irreversibly in the short run are also coping with fringe areas of newly saline soils. Some strategies that have been successful in the past are growing strips of alfalfa along road ditches to reduce encroachment into fields, eliminating fallow in favor of continuous cropping, including deep-rooted, long-season crops in the rotation, and even including alfalfa as part of a long-term rotational strategy. Much press has been devoted to the effects of flooding on the loss of farm ground, but little has been said about the less obvious problems associated with the increase in saline acres in these areas.
Nitrogen management is more possible than many areas due to our fall soil test. However, in 1998, many fields experienced unanticipated N losses due to leaching and denitrification. Leaching was prevalent in sandier soils, while denitrification was worse than normal in heavier clay soils. Both situations contributed to yellowing of crops in many areas. The lesson hopefully learned because of these experiences is that split application of N may be necessary to ensure adequate N through the season on soils sensitive to leaching or denitrification. The answer is not increasing N rates preplant or in the fall, hoping that the added N will compensate for loss. Water will move 300 lb N/acre through the soil as easily as 100 lb/acre if that is the concentration in the water. The solution is to split the application reasonably and use appropriate soil and plant analysis to guide the applications.
1998 was a tough year in North Dakota agriculture. To weather these times, wise production decisions must be made. Sometimes it is many years before lessons learned from a year can be recalled to help solve a future problem, but eventually these experiences recur. Some experiences are immediately useful. As many guesses as possible need to be eliminated from a farm production plan. Although about one-third of North Dakota fields are regularly soil tested, the rest are not. Producers need to know that certain inputs are or are not needed, not guess that they are. Soil testing each field will help to increase the impact of fertilizer production inputs and make certain that the right nutrients are applied for each crop.
Dr. Dave Franzen
NDSU Extension Soil Specialist