Number 376 November 9, 2012

Transcription

1 Number 376 November 9, Update on nitrate levels in forages this fall in Kansas 2. Grain sorghum row spacing research in Kansas 3. Examine soils and look for signs of compaction 4. Deep tillage considerations 5. Comparative Vegetation Condition Report: October 23 November 5 1. Update on nitrate levels in forages this fall in Kansas We continue to have problems with high nitrate levels in forages this fall, especially in cereals such as wheat, rye, oats, barley, and triticale planted early for fall grazing following drought-damaged corn or sorghum, and in brassica crops such as canola, turnips, rape, kale, rutabagas, and tillage radishes. Since July 1, the K-State Soil Testing Laboratory has analyzed more than 1,200 forage samples from farmers and ranchers for nitrates. The following is a brief summary of what we have found in October: Fall cereals, including wheat, rye, oats barley and triticale: 37 samples Mean nitrate level of 10,039 ppm Range of 130 to 38,990 ppm 17, or 46% of total, had levels greater than 6,000 ppm. Brassicas for fall grazing, including turnips and radishes: 36 samples Mean nitrate level of 27,442 ppm Range of 16 to 81,279 ppm All but 4 samples had levels greater than 6,000 ppm. Volunteer corn: 19 samples Mean nitrate level of 7,037 ppm Range of ,200 ppm 10, or 53% of total, had levels greater than 6,000 ppm Corn stalks, baled or standing in the field: 100 samples Mean nitrate level of 3,922 ppm Range of 18 to 20,488 ppm 18, or 18% of total, had levels greater than 6,000 ppm 1

2 Grain sorghum stalks, baled or standing in the field: 78 samples Mean nitrate level of 1,791 ppm Range of 27 to 23,333 ppm Only 6 samples, or 8% of total, had levels greater than 6,000 ppm Sudangrass, forage sorghum, cane, etc.: 115 samples Mean nitrate content of 3,503 ppm Range of 19 to 18,400 ppm nitrate 24 samples, or 21% of total, had levels greater than 6,000 ppm Silage (corn and sorghum): Only 12 samples, but all were below 1,500 ppm There are a couple of key take home messages from these samples. First, most of the forages we will likely be using for supplemental feed this winter have the potential to contain toxic levels of nitrates. Whether grazing corn or grain sorghum stalks, feeding baled stalks, or using late-summer or fallplanted forages such as wheat or other cereals, or brassicas such as turnips, radishes or canola, TEST IT FIRST. The brassicas such and turnips and radishes are known accumulators of nitrate, and samples to date confirm that. Be especially careful when utilizing these materials for grazing. Nearly all the samples tested to date have extremely high levels of nitrate. Volunteer corn is another problem. More than half the samples identified as volunteer corn had high nitrate levels. This is a special problem as the nitrate level will not go down as these plants die, and this material will be preferred grazing for many cows and calves compared to the stalks in the field from the full-season crops. The good news from the sampling to date is a high percentage of the sorghum stalks have relatively low nitrate levels. Some are high, however, so testing individual fields will be important. If nitrate levels are acceptable, these acres could be available for grazing. Also, about 75 percent of the sudan and forage sorghum forage samples tested by our lab have low nitrate levels. These are important supplemental forages for many Kansas cattlemen. In summary, nitrate levels in many forages in Kansas are high this fall, and likely will stay that way until spring. This will require careful sampling of forage supplies to avoid nitrate poisoning of livestock this winter. -- Dave Mengel, Soil Fertility Specialist dmengel@ksu.edu 2

3 2. Grain sorghum planting configuration research in Kansas (Editor s Note: This article is an excerpt, slightly modified, from the new K-State publication Efficient Crop Water Use in Kansas, NF-3066, available at: -- Steve Watson) Planting configuration often has an effect on grain sorghum yields. Much of the effect has to do with the efficiency of water use. Grain sorghum is typically described as a more drought-tolerant crop than corn or soybeans. The grain sorghum plant is able to shut down during dry weather and wait for conditions to improve, while tillering profusely when growing conditions are good in order to take advantage of the environment. A consistent supply of water is not as critical to grain sorghum, but water availability is still important to yield. Row spacing is one example of planting configuration effects on sorghum yields. Former K-State agronomists Barney Gordon and Scott Staggenborg reported no benefit to 15-inch over 30-inch rows when grain sorghum was planted mid-may, but a 29-bushel-per-acre advantage to 15-inch rows compared to 30-inch when grain sorghum was planted in mid-june. Other research by Staggenborg indicated that 10-inch rows may consistently yield more than 30-inch rows, when yield potential is over 100 bushels per acre, and 30-inch rows may yield more than 20-inch rows when the yield potential is less than 100 bushels per acre. Manhattan 1995 Effect of Row Spacing on Grain Sorghum Yields Powhattan Belleville Manhattan Belleville Manhattan Grain yield (bu/acre) averaged over all planting dates, populations, and hybrids Wellington 1997 Row spacing (in.) LSD (0.05) 12.2 NS NS A skip-row configuration is another technique producers may employ to enhance yield. skip-row grain sorghum was evaluated in 2007 to 2009 in Colby, Tribune, and Garden City. No advantage was observed in growing grain sorghum in a plant two/skip two row pattern compared to grain sorghum planted every row. A disadvantage was found when growing conditions were good, with a substantial reduction in yield observed. Effect of Skip Row Planting on Grain Sorghum Crop Pattern Tribune ( ) Garden City (2008- Colby ( ) 2009) Yield (bu/acre) Grain sorghum Every row Skip row LSD (0.05) Finally, clumped planting of grain sorghum is a technique that may have an opportunity to improve or stabilize grain sorghum yields under dryland conditions. Clump planting is the process in which sorghum seeds are planted together (approximately 4 to 5 seeds) on 30-inch rows. This clumping 3

4 allows the farmer to have some control over grain sorghum tiller development by decreasing earlyseason tiller onset. This reduction allows for more soil water to be available to the plant during reproduction. At the Southwest Research-Extension Center at Tribune, Lucas Haag and Alan Schlegel reported that grain sorghum planted in clumps yielded 58 bushels per acre, whereas 30-inch grain sorghum yielded 51.2 bushels per acre during a 3-year study, 2006 to Rob Aiken, research crop scientist at the Northwest Research-Extension Center, graduate student Kalaiyarasi Pidaran, and other K-State agronomists found that clump planting had a yield advantage of 10 bu/acre of more in two of seven environments (Colby 2009, June 24 planting date; and Garden City 2010). Clumped planted reduced grain yield in the highest yielding environment (Colby 2009, May 21 planting date). Treatment Colby, planted May 21, 2009 Sorghum Yield As Affected by Planting Geometry Colby, Colby 2010 Garden City Garden City planted June 24, 2009 Tribune 2009 Tribune 2010 Uniform Clumped Kraig Roozeboom, Cropping Systems Agronomist kraig@ksu.edu 3. Examine soils and look for signs of compaction There have been many questions recently about soil compaction. This a good time to get out and investigate soil profiles for signs of compaction. There is much you can learn by pushing a tile or soil probe into the ground. First, if you have never done so, you can learn something about the soil profile. How many inches of topsoil do you have? At what depth do you encounter changes in soil textures? Topsoil thickness and soil texture are two properties you can t really control, at least not in the short term. One thing you can certainly look for and work on improving, however, is the density of your soil and whether there are any layers of compaction. Scientific approach: Density refers to the mass of a substance divided by its volume. In soil, we measure density (which we call bulk density) by pounding a cylinder of a known volume into the soil, and then drying the soil for two days in an oven. This gives us the oven dry mass, which we divide by the volume, and thus have the bulk density. There are detailed instructions available for this procedure online at In scientific research, this method is used to analyze the effects of different management practices on soil quality, the differences between soil types, and other factors. It can also be used to quantify the differences in soil density at various depths within the soil, which helps in research on soil compaction. Hands-on approach: The scientific approach is not especially useful for producers and others to find compaction layers in their soils, however. There are much easier methods, with a level of precision that is good enough for practical use. Using a spade, soil probe, or tile probe is a good way to learn something about your soil profile and whether there may be a compaction layer. One approach is to dig a small hole about a foot deep, as if you were digging a post hole. You can take a knife and poke 4

5 into the side of the hole, feeling for layers that seem denser, or that have a platy, compressed soil structure. Use a tape measure to determine the depth at which the dense layers occur. Then walk to a nearby fence row or waterway and do the same thing. Does this soil look and feel different? How does this compare to the endrows? Once you determine the depth at which the compaction occurs, you can work on solutions for improving (decreasing) the density of the compacted layer, or the soil in general. If compaction seems limited to the upper 3 inches of the soil profile, then the most likely culprit is traffic. Running properly inflated tires, using floatation tires, and having more tires in general helps to decrease surface compaction. Of course it will also help to keep traffic off the soil as much as possible when the soil is wet. A tougher problem to solve is subsurface compaction. If you can feel a layer that is compacted at depths greater than 6 inches, you may be dealing with subsurface compaction. Subsurface compaction should not be confused with a change in the soil texture. It is common to observe changes in the soil texture as you go deeper in the soil profile. Many soils have an increase in clay content in the upper part of the subsoil, which is natural and took thousands of years to form. Some soils, such as those in floodplains, might have sandy layers present beneath the surface. This is the reason why the spade/post hole method is really the best, because it allows a person to discover so much more about the soil profile than using a tile probe alone. Digging a small hole with a spade is the best way to learn about the soil s natural and unnatural layers, such as compacted layers. Use a knife to feel for any unusually dense layers, and a tape measure to determine the depth of the layer. Photos courtesy of DeAnn Presley, K-State Research and Extension. 5

6 Large pieces of soil that are horizontally oriented, or platy, are a sign of compaction. -- DeAnn Presley, Soil Management Specialist deann@ksu.edu 4. Deep tillage considerations Now that row crop harvest is over in most areas, producers might be considering deep tillage for the purpose of alleviating compaction. Here are a few things to consider. How deep should the tillage operation occur? That is best answered by taking a spade or soil probe out in your field and digging a few holes. Ideally, you should dig down to about 18 inches. You are looking for dense layers that are restricting plant roots. If you see platy soil structure, which looks like many horizontal layers of soil about ¼ to ½ thick in diameter, look to see if the roots have penetrated through this zone in the soil. If the roots have predominantly penetrated this zone, that probably means that the layer isn t really root-limiting. If you see a lot of roots that are growing horizontally, or if they appear stubby and gnarled, lacking many root hairs, that can also be a sign that the roots are having trouble making it through this layer. So if you see a dense zone at say 8 inches, you d only want to go about 9 inches deep with the tillage operation. As you double the depth of the tillage operation, you quadruple the power requirement, so going too deep is a waste of time and energy. Also, there is no point in going deeper and potentially damaging the soil profile even further (risks are explained below). 6

7 Is deep tillage going to be of benefit to future crop yields? In research studies, it is commonly concluded that deep tillage is only beneficial if the zone of compaction is truly root limiting. If it isn t, deep tillage probably won t be of much benefit. The only way to really know is to leave about 3-5 untilled strips through your field and then compare the yields in those areas to the tilled parts of the field next year easy enough to do if you have a yield monitor and you mark the locations of those untilled strips. How long does the effect produced by deep tillage last? If the field is subsequently conventionally tilled, the benefit will probably only last a few years, due to the many trips made across the field with various tillage and other implements. If the field is subsequently no-tilled and traffic is controlled, the effect of a single deep tillage operation might last longer. Are there any negative side effects of deep tillage? If tillage is performed when the soil is too wet, the zone of compaction could be moved even deeper. To know if the soil is too wet for tillage, try to make a ribbon out of the soil without wetting it. If you can make a texture ribbon, it is too wet. Alternatively, if you can roll out a snake of soil by rubbing it between your palms, it s too wet. This is called plasticity and if the soil is plastic (bendable) it can smear and compact easily. You ll need your shovel or soil probe to test this to the entire depth that you want to till. Your goal is to create fracture, so the soil has to be dry enough to shatter, not smear. To see if you re achieving this, dig between the shanks with a spade and see if the soil is loosened. If you bring up huge clods, the soil isn t shattering and it would be better to wait until it s drier. Straight shanks are going to cause the least amount of soil disturbance, as shown in the photos below. 7

8 This image was taken 6 weeks after tillage with a ripper designed for minimum surface disturbance as it has straight shanks. The spade could be easily pushed all the way into the soil. Between the shanks was easy to dig, except for in the end rows where there was a lot of traffic from heavily loaded grain carts. The implement used in this field is shown below. Photos by DeAnn Presley, K-State Research and Extension. 8

9 Also, keep in mind that certain areas of the field are more compacted than others. Those areas might not be ready for deep tillage at the same time as the rest of the field because compacted areas tend to stay wetter, longer. A case in point is a recent trip that I made to an Ellis County producer s farm. I observed soil shattering from deep tillage across the entire 30 inches between the shanks in the average part of the field, but in the end rows where the grain cart was driven, I dug up clods that were about one cubic foot in size, most likely because the more compacted areas were wetter. Is deep tillage economical? Only if a root-limiting layer is really present, and even then this is a costly operation due to the fact that it requires a lot of power to go deep. Deep tillage is slow-going and the implements are not very wide. As a result, deep tillage requires a lot of operator time, diesel fuel, and usually a few shear bolts! How can you prevent compaction? Deep compaction is caused by heavy axle loads. Research indicates that axle loads greater than 10 tons can cause compaction as deep as 12 to 18 inches, and many modern implements weigh well over 10 tons per axle. The only way to reduce axle weight is to decrease the load weight or add axles axle load cannot be reduced by adding more or larger tires, unfortunately. For more information on deep tillage, please contact me at the address below or at DeAnn Presley, Soil Management Specialist deann@ksu.edu 9

10 5. Comparative Vegetation Condition Report: October 23 November 5 K-State s Ecology and Agriculture Spatial Analysis Laboratory (EASAL) produces weekly Vegetation Condition Report maps. These maps can be a valuable tool for making crop selection and marketing decisions. Two short videos of Dr. Kevin Price explaining the development of these maps can be viewed on YouTube at: The objective of these reports is to provide users with a means of assessing the relative condition of crops and grassland. The maps can be used to assess current plant growth rates, as well as comparisons to the previous year and relative to the 21-year average. The report is used by individual farmers and ranchers, the commodities market, and political leaders for assessing factors such as production potential and drought impact across their state. NOTE TO READERS: The maps below represent a subset of the maps available from the EASAL group. If you d like digital copies of the entire map series please contact Kevin Price at kpprice@ksu.edu and we can place you on our list to receive the entire dataset each week as they are produced. The maps are normally first available on Wednesday of each week, unless there is a delay in the posting of the data by EROS Data Center where we obtain the raw data used to make the maps. These maps are provided for free as a service of the Department of Agronomy and K-State Research and Extension. The maps in this issue of the newsletter show the current vegetation conditions in Kansas, the Corn Belt, and the continental U.S, with comments from Mary Knapp, state climatologist: 10

11 Map 1. The Vegetation Condition Report for Kansas for October 23 November 5 from K-State s Ecology and Agriculture Spatial Analysis Laboratory shows that active plant growth is limited to parts of east central Kansas, where temperatures have been milder and moisture more plentiful. Very little photosynthetic activity is visible from the winter wheat in western Kansas. 11

12 Map 2. Compared to the previous year at this time for Kansas, the current Vegetation Condition Report for September October 23 November 5 from K-State s Ecology and Agriculture Spatial Analysis Laboratory shows that vegetation conditions are better along the eastern counties as well as parts of Hodgeman and Ness counties. These areas are still seeing the benefit from September moisture. 12

13 Map 3. Compared to the 23-year average at this time for Kansas, this year s Vegetation Condition Report for October 23 November 5 from K-State s Ecology and Agriculture Spatial Analysis Laboratory shows that areas of Hodgeman and Ness counties have above-average NDVI values. The eastern counties also have above-average NDVI values. Unfortunately, this is likely due to a flush of annual weeds, rather than marked improvement in pasture conditions. 13

14 Map 4. The Vegetation Condition Report for the Corn Belt for October 23 November 5 from K-State s Ecology and Agriculture Spatial Analysis Laboratory shows that southern Missouri and the northeastern corner of Minnesota have the highest NDVI values in the region. Missouri continues to benefit from the late-season rainfall. 14

15 Map 5. The comparison to last year in the Corn Belt for the period October 23 November 5 from K-State s Ecology and Agriculture Spatial Analysis Laboratory shows that there has been a big decrease in biomass production in the Northern Plains. This is particularly visible in western Minnesota and in the eastern portion of the region. Note there is a splice line in eastern Ohio that affects the comparison in that region. 15

16 Map 6. Compared to the 23-year average at this time for the Corn Belt, this year s Vegetation Condition Report for October 23 November 5 from K-State s Ecology and Agriculture Spatial Analysis Laboratory shows that northeastern Minnesota and northern Michigan have above-average NDVI values, while western Ohio and eastern Kentucky are showing below-average values. Southeast Kansas and southwestern Missouri have more active production than usual, due primarily to the more favorable moisture conditions this fall. 16

17 Map 7. The Vegetation Condition Report for the U.S. for October 23 November 5 from K-State s Ecology and Agriculture Spatial Analysis Laboratory shows that northern California and western Oregon are the bright spots in the west, while the South also continues to have active biomass production. There is a very pronounced splice line in eastern Ohio that affects the condition reports in that area. 17

18 Map 8. The U.S. comparison to last year at this time for the period October 23 November 5 from K-State s Ecology and Agriculture Spatial Analysis Laboratory shows that Texas and parts of Missouri have greater biomass production. The Northern Plains and much of the Northeast are showing lower NDVI values. Again, a splice line is prominent in eastern Ohio, and is the result of cloud cover issues in the area. 18

19 Map 9. The U.S. comparison to the 23-year average for the period October 23 November 5 from K-State s Ecology and Agriculture Spatial Analysis Laboratory shows that areas of above-average biomass production are concentrated in the lower Mississippi area, while the Northern Plains, the Pacific Northwest, and southern New England are showing lower-than-average values. -- Mary Knapp, State Climatologist mknapp@ksu.edu -- Kevin Price, Agronomy and Geography, Remote Sensing, Natural Resources, GIS kpprice@ksu.edu -- Nan An, Graduate Research Assistant, Ecology & Agriculture Spatial Analysis Laboratory (EASAL) nanan@ksu.edu These e-updates are a regular weekly item from K-State Extension Agronomy and Steve Watson, Agronomy e-update Editor. All of the Research and Extension faculty in Agronomy will be involved as sources from time to time. If you have any questions or suggestions for topics you'd like to have us address in this weekly update, contact Steve Watson, swatson@ksu.edu, Jim Shroyer, Crop Production Specialist jshroyer@ksu.edu, or Curtis Thompson, Extension Agronomy State Leader and Weed Management Specialist cthompso@ksu.edu. 19