Agronomy Notes
September, 2003
CONTENTS:
FORAGE
CORN
SORGHUM
WHEAT
SOYBEANS
COTTON
Dr. David Lang
The wet summer has been poor for making high quality hay. Much of the hay crop has been cut when it's too mature. The wet soil conditions have prolonged drying conditions with much of the hay rained on again after it was cut. Mold is a problem and hay may be prone to catching on fire if the moisture level is greater than 22-25%. Internal bale temperature should be monitored with a 12 to 24 inch long thermometer and bales greater than 160 degrees should be left outside well away from storage facilities until their temperature drops to less than 150 degrees.
Forage growth has also been reduced due the extensive cloudy days and saturated soil moisture conditions. Plant roots need oxygen to function properly and excessive soil water reduces the amount of oxygen available to the roots.
Pastures are generally in good condition. Grazing has been the best way to utilize forage this summer. Hay could be in short supply this winter. Planting winter annuals will help provide winter grazing. Last year, ryegrass planted early (August to September) was plagued by a plant disease called Blast or gray leaf spot. It occurred because of the tropical rains we had in September and early October last year. Later plantings (October) of ryegrass were not nearly as affected. Small grains (oat, wheat, rye) are also not affected by Blast, so growers should consider planting these in a mixture with ryegrass. Planting some ryegrass acreage later will also help to avoid Blast. The last outbreak of Blast was about ten years ago with similar conditions, so Blast does not happen every year. If our wet conditions continue into the fall of 2003, Blast may be back again this year, so take some steps to minimize its impact.
Dr. Erick Larson
Pollination Problems - There have been an abnormally high number of pollination problems in corn fields this season. This is particularly strange since barrenness is normally associated with severe water deficit and/or high temperatures, neither of which occurred this season. I believe many of these cases resulted from herbicide injury from postemergence application or off-target drift. Some cases appear to have resulted from in-season over-the-top application of sulfonylurea herbicides (Steadfast, Option, Accent, Beacon, etc...). In-season applications of Lightning on CLEARFIELD herbicide tolerant corn also produced severe barrenness in many fields in northeast Mississippi. The locations experiencing injury received abnormally abundant rainfall and stayed saturated through much of May and early June. These saturated conditions likely promoted herbicide injury which was sustained through when ear development initiated. Growers should closely observe their fields for irregular ears and evidence of herbicide injury, so they can adjust their management, if needed, to avoid problems in the future. For instance, some corn hybrids are more sensitive to sulfonylurea herbicides than normal. Some sulfonylurea herbicides, particularly Steadfast and Basis Gold, have more frequently produced crop injury than other herbicides in this family. Also, the herbicide tolerance of CLEARFIELD corn apparently may be substantially influenced by environmental conditions.
Dr. Erick Larson
Head Sprouting: The extraordinary rainy, humid weather the year before last promoted extensive kernel sprouting in many row crops; especially devastating grain sorghum. The only way to prevent sorghum kernel sprouting is to harvest it before environmental conditions encourage moisture accumulation. Sorghum is more susceptible than corn to pre-harvest sprouting (kernel moisture of 23-25% and 80-90 degree F conditions are ideal). Thus, considering we are enduring an abnormally wet summer, sorghum growers may consider mechanically drying sorghum or taking some moisture dockage to avoid environmental exposure capable of promoting kernel sprouting.
Desiccant/Sorghum Moisture: After sorghum kernels reach physiological maturity, application of a pre-harvest desiccant will not influence kernel moisture. Sorghum physiological maturity is signified by a hard kernel and presence of a black spot opposite the embryo at the base of the kernel (similar to the black layer in corn). Kernel moisture will likely be 25-30% at physiological maturity. Kernel drying rate after physiological maturity is entirely dependent upon environmental conditions. Application of a pre-harvest desiccant may aid harvest progress by killing green vegetation and immature kernels on ""sucker"" heads on late tillers. The presence of these sources in a combine-harvested grain sorghum sample would raise measured moisture content of the sample.
Dr. Erick Larson
Wheat Varieties - The 2003 MSU Wheat Variety Trials are now available on the MSUcares.com website or at your county extension office. Variety evaluation should be based primarily upon yield history (particularly on different soil types or management regimes), plant characteristics (including maturity, straw strength and height) and disease resistance for predominant pathogens in the region.
Dr. Alan Blaine
Over the last several weeks numerous questions have surfaced regarding late season problems, predominantly foliar diseases and insects.
Foliar diseases are a concern, but you must keep several points in mind. For instance, varietal resistance is the best approach especially for diseases such as stem canker and SDS (Sudden Death Syndrome). Also, you cannot control all foliar diseases with a fungicide and once established it is usually too late to benefit from a fungicide application.
Disease control must be approached from a preventative standpoint not after the fact. I recognize this is a difficult approach for many, but in order to take yields to the next level it will require this approach. In addition to the use of foliar fungicides, it will require the utilization of other late season management options as needed.
We have the potential for an excellent soybean crop. As of early September we were approximately one-third harvested and yields have been well above average. If we do not experience any harvest problems this will be the best crop ever grown in Mississippi. I fully expect state average yields to be 36-37 bushels per acre.
However, this crop could have been bigger, but it would have required additional fine tuning on the tail end. I have had hundreds of calls in the last three weeks regarding the use of Quadris. In most situations it was obvious that producers were starting to see some disease and wanting to do something about it. In most of those cases an application was too late.
Quadris is effective in reducing losses from anthracnose and pod and stem blight with its strong suit being aerial blight. It will prevent frogeye, when applied before the disease occurs. However, most have been asking about the yellow/bronze discoloration they are seeing on the foliage late season. This is late season cercospora which is the same disease that causes the purple stain observed on seed from time to time. Quadris is not effective on late season cercospora. As other diseases are controlled, late season cercospora becomes the predominant disease. Our best option for preventing losses from cercospora is Topsin M, although it is similar to Benlate it does not appear to do as good a job and it is expensive. Currently we are looking at tank mixes of Quadris and Topsin M in an effort to reduce cost, and broaden the spectrum, but we hope some additional options will be available soon.
In addition to late season cercospora, we have encountered more frogeye leafspot than we have observed in several years. Frogeye can be controlled, but applications need to be made prior to the onset of disease, thus a preventative approach.
In our verification program (SMART) we applied Quadris and Dimlin to all our Group V fields. These were all irrigated fields. We applied 4 ozs. of Quadris plus 2 ozs. of Dimilin per acre. Applications began in mid-July and were complete by early August. Fields this year are scattered from Tunica to Valley Park.
As you look at these dates you can see that we were making this application early before problems started showing up. Soybeans look good, and we anxiously await harvest.
Some may be skeptical of making this application; because, we do not have the same disease pressure every year. However, to achieve the full benefits, think preventative. I personally feel if you irrigate you should consider an application such as this every year. Our work has shown yield increases as high as 14 bushels per acre. Although, there are years the response is minimal. We feel that it will at least pay for itself. In other words, it may not make you anything, but it will not cost you either.
I often have growers tell me, "Beans are too cheap I cannot afford to do these things". I ask you to consider when do you need to make higher yields when prices are high or low. You have to give to get, and if we do not take a preventative approach to disease control, we will continue to experience yield losses from time to time.
As harvest began, numerous questions surfaced regarding the use of desiccants. I personally feel we are often too quick to apply desiccants. Desiccants should be utilized primarily in the event of a failure in weed control or in the case of late emerging weeds particularly vines. You will find that most of the green vegetation (grasses) will go through the combine and contribute little if any to moisture or foreign matter.
Desiccants will not turn green butter beans into dry soybeans. It will dry stems in the upper portion of the plant and knock off leaves but usually if a field has seed at harvest moisture plant material will go through the machine. Do not be too quick to put out a harvest aid, first ask yourself the question, "Will it pay for itself?". If you feel an application is needed, the two best options are Roundup (8-10 days prior to harvest), or a mixture of Gramoxone Max at .25 lb. ai/acre plus 3 lb.. of Sodium Chlorate and a .25% surfactant. This second option is fairly fast depending on what you want to accomplish and your timing. The tank mix has proven to work better than either material applied alone.
Let's pay attention to late season management and protect the crop on the tail end versus quitting too soon.
Dr. Will McCarty
Cotton defoliation and harvest operations are going at full tilt in most all the cotton growing areas. Late planted and late maturing cotton will need as much time as nature will allow.
Even though this crop had a cool start, it looks like it will do a little better than OK. There are some areas where dry weather will hurt yields, but I feel that we have an excellent chance of making the USDA production estimate. The August Crop Production Estimate placed this crop at 808 pounds of lint per acre from some 1,100,000 harvested acres. As I said, with good harvesting weather, we have a good chance of exceeding this estimate; however, do not count the crop till it is bagged and tied.
Boll Counting - Each year I get numerous questions about making boll counts. Generally speaking, counting bolls per acre can provide you with a pretty good estimate of the number of bolls per acre in a field, not much else. Using boll counts to estimate yield can be vague at best. As a rough rule, it takes about 127,000 - 128,000 4.5 gram (seed cotton) bolls to produce a bale of cotton. That is at 38% turn out and no consideration for harvest efficiency. More realistically you are looking at about 150,000 bolls being required to produce a bale of lint. This may vary from variety to variety, from field to field, and from year to year. Therefore, boll counts are perhaps better than nothing at estimating yield, but not much.
Estimating Yield By Boll Counting Estimating yield by counting bolls can often be misleading. Variation in boll size, lint percent, future weather conditions, harvest losses and ginning losses can all effect how boll counts relate to final yield. However variable, people associated with cotton will at some point try to use boll counts to estimate production or make comparisons. Personally, to me, a boll count is just that - an estimate of how many boll per acre a crop contains - nothing more.
The following tables are designed to help you estimate yields using boll counts.
Following are some suggestions for using these tables:
1. Count all harvestable bolls on at least 10 feet of row selected at random in at least four representative locations in the field. Using this data calculate an average number of harvestable bolls per row foot.
2. Establish an estimate of boll size. Two suggestions - a) At random, pick all the seedcotton from 50 to 100 bolls representing all boll sizes on the plant. Weigh the composite sample on an accurate scale calibrated in grams. Divide the weight (in grams) by the number of bolls picked and this will give an approximate average boll weight for the field. This calculation should be made for several samples taken to represent the field. b) Pick all the seedcotton from all harvestable bolls on each of ten randomly selected plants and keep an accurate count of all bolls picked. Weigh the composite sample on an accurate scale calibrated in grams. Divide the weight (in grams) by the number of bolls picked and this will give an approximate average boll weight for the field. This calculation should be made for several samples taken to represent the field.
3. Once average boll size and average number of bolls per row foot are established, go to the appropriate table based on expected turnout (33 to 35% is a good average) and determine how many bolls are estimated to be required per row foot to make a 480 pound bale of cotton. To determine estimated yield in bales per acre, divide the number of bolls per row foot counted by the number required per bale from the table.
Example - 40 inch rows, average 16 bolls per row foot, average boll weight 3.5 grams (rounded off to the nearest one half gram) and an expected turnout of 35% - Go to Table 3 (for 35% turnout), go to the 40 inch row line, follow across to the 3.5 gram per boll column and you find that 12.5 bolls per row foot are required to press a 480 pound bale of lint per acre. 16 bolls per row foot divided by 12.5 is equal to an estimated yield of 1.3 bales per acre. Note the word estimated is in bold text - this is only an estimate.
Table
1 Calculated
bolls per row foot needed to produce one bale (480#
lint) per acre at various row spacing and boll
weights.
Table
2 Calculated
bolls per row foot needed to produce one bale (480#
lint) per acre at various row spacing and boll
weights.
Table
3 Calculated
bolls per row foot needed to produce one bale (480#
lint) per acre at various row spacing and boll
weights.
Table
4 Calculated
bolls per row foot needed to produce one bale (480#
lint) per acre at various row spacing and boll
weights.
Table
5 Calculated
bolls per row foot needed to produce one bale (480#
lint) per acre at various row spacing and boll
weights.