As you are in the combine cab, lamenting the yield loss that the drought stole from you, many folks will be thinking, “What is next?” A shortage of moisture for much of the growing season is one thing, but what are the ramifications of dry soils as we move forward. There are quite a few of those, and this is an incomplete list.

The drought has not only taken a toll on yields of row crops, small grains and pasture, but has left a negative legacy that will impact the economy for months to come, and will impact the agronomic resources of the Corn Belt for an undetermined length of time.

1. Soil Moisture

One of the first concerns is the lack of moisture going into the 2013 growing season. Currently, topsoil and subsoil moisture (pdf) resources are slim to none in the Corn Belt. 

·      IL: Topsoil moisture 62% very short, 29% short, 9% adequate. Subsoil moisture 75% very short, 22% short, 3% adequate. 

·      IN: Topsoil moisture 34% very short, 39% short, 27% adequate. Subsoil moisture 54% very short, 33% short, 13% adequate. 

·      IA: Topsoil moisture level is unchanged from last week at 60% very short, 31% short, 9% adequate and 0% surplus. Subsoil moisture also remains unchanged from last week at 70% very short, 26% short, 4% adequate, and 0 percent surplus.

·      KS: Topsoil moisture 74% very short, 23% short, 3% adequate, 0% surplus. Subsoil moisture 73% very short, 24% short, 3% adequate, 0% surplus.

·      MI: Topsoil moisture 7% very short, 25% short, 62% adequate, 6% surplus. Subsoil moisture 21% very short, 35% short, 41% adequate, 3% surplus. 

·      MN: Topsoil moisture 16% Very Short, 38% Short, 45% Adequate, and 1% Surplus.

·      MO: Topsoil moisture 90% very short, 9% short, 1% adequate. Subsoil moisture supply 90% short, 9% short, 1% adequate. 

·      NE: Topsoil moisture 69% very short, 28% short, 3% adequate. Subsoil moisture 69% very short, 27% short, 4% adequate. 

·      ND: Topsoil moisture 15% very short, 46% short, 38% adequate, 1% surplus. Subsoil moisture 15% very short, 47% short, 37% adequate, 1% surplus. 

·      OH: Topsoil moisture 29% very short, 39% short, 32% adequate, 0% surplus. 

·      SD: Topsoil moisture 51% very short, 30% short, 19% adequate. Subsoil moisture 56% very short, 27% short, 16% adequate, 1% surplus. 

·      WI: Topsoil moisture 23% very short, 39% short, 37% adequate, and 1% surplus.

With soil moisture levels low, some areas will need to collect 6-10 in. of precipitation over the fall and winter to get back to normal. In all likelihood that is possible to collect that much, but force of the rain and the degree to which the ground is frozen will limit the potential for success. While snow will melt more slowly and have a greater chance of being absorbed, an uneven distribution of the snow will cause spot shortages.

2. Fall Tillage

Many fields will have a chisel plow in operation close behind the combine trying to break up any compaction and begin burying cornstalks for degradation and disease elimination. But with dry weather, will the soil work smoothly or turn up in chunks that will create havoc with creating a good seedbed in the spring? That issue has a wide variety of answers, and will depend on the extent of any precipitation, whether there is any moisture left in the soil, and the soil type. 

University of Illinois crop production specialist Emerson Nafzigersays so far the soil is working satisfactorily, and he says he is not surprised. “Tillage last fall and field operations this year all took place when soils were relatively dry, so there has been little of the compaction that normally results from heavy equipment on moist soils. While rainfall does not really cause much compaction – it simply can't produce the high weight loads needed – it does cause surface soils to run together to form a hard surface that often means more water running off slopes. So expect soils to be mellower than normal during fall tillage, and match the tillage operation, if any is needed, to this condition.”

3. Cover crop for moisture and nitrogen preservation

How much of your applied nitrogen was used by the corn, or not-used by the corn and may still remain in the soil? If any remains, the rain you are hoping for may leach the N out of the soil and it is lost to you. Many producers will be planting a cover crop this fall to collect the N and recycle it to the next crop when the cover crop is plowed under. Nafziger says the soybeans following corn will use the nutrient, but he said it is hard to determine what left over nitrogen will be hanging around for use by second year corn. That is supported by University of Wisconsin research (pdf), which addresses cover crops after a drought, “One benefit of planting cover crops after corn silage, small grain, or a processing vegetable crop, or after a manure application is that the cover crop can take up residual nitrate and reduce the risk of nitrate leaching between harvest and planting. Other benefits of cover crops include reduction in soil erosion and weed suppression.” While one federal program to finance cover crop planting expired last week, others have been announced, which may be available at FSA or NRCS offices.

There are myriad cover crops, from grasses that establish quickly and trap nitrates to brassicas, such as radishes, turnips and other that have other benefits. The N taken up by a cover crop is cycled back into the soil during the decomposition of the plant biomass. The release of N into the soil is, in-part, a function of the carbon to nitrogen (C:N) ratio of the plant material, according to the Wisconsin research. For more information about planting cover crops and their benefits, consult the Midwest Cover Crop Council.

4. Soil testing after a drought

All summer you were convinced your corn was displaying symptoms of a lack of P and K, but were always told it was a result of the drought, and the lack of moisture uptake prevented adequate absorption of P and K for the benefit of the corn stalk. After crops come out of the field, you will be able to take the soil tests you thought were needed, but unfortunately, fertility researchers at Iowa State University will tell you that the soil tests will also show results that stem from the drought. The Iowa State researchers advise that, “No matter the option used to estimate grain or biomass P and K concentrations, there is a great deal of uncertainty and variability concerning drought effects. Depending on moisture availability during different portions of the growing season, there could be relatively more or less grain dry matter production than nutrient uptake and translocation from vegetative plant parts to the grain, which would result in lower or higher concentrations, respectively.” 

The problem with P & K measurement is the fact that dry soils do not give adequate measurement because the lack of rainfall has prevented certain salts in the topsoil to leach out, and it is difficult to interpret the readings provided by a soil testing company. They advise to wait until the soil has better moisture resources before taking a soil sample. An alternative is to compute the amount of P and K removed from the field by the grain and/or biomass that you may have harvested. “For example, values from PM 1688 for corn grain are 0.375 lb P₂O₅/bu and 0.30 lb P₂O/bu; and for soybean grain values are 0.80 lb P₂O₅/bu and 1.5 lb K₂O/bu.” 

There is also a problem with good soil testing after a drought, according to the Iowa State fertility specialists, which is difficulty in controlling the sampling depth in dry soil, and particularly dealing with the powdery soil at the upper layer of the profile.

Summary

The drought will result in many issues that farmers typically can avoid during a more regular year. However, there will be both challenges and opportunities that result from the change, whether it be in tillage or nutrient management. There obviously are many more such issues, and they will be explored as they are identified. 

Read the article at Farmgate blog.