Agronomy Notes

July, 2004

New MSU cotton specialist named

MISSISSIPPI STATE -- The new Extension cotton specialist at Mississippi State University is a weed scientist who is no stranger to MSU or agronomic crops.

Before Tom Barber was named the MSU Extension Service cotton specialist on July 1, he spent three and a half years at MSU working with cotton and corn. Most recently, he was responsible for managing 170 acres of remote sensing, site-specific precision agriculture and weed control field and plot research.

The Arkansas native earned his doctorate in the Department of Plant and Soil Science from MSU in 2004. He received both his bachelor's and master's degrees from the University of Arkansas in agronomy and weed science.

Barber replaces Dr. Will McCarty who served in this position for the last two decades. Dr. McCarty is now the assistant director/state program leader for Extension Agriculture and Natural Resources.

Tom's wife, Scharidi, is a Research Technician in the Poultry Science Department. Tom and Scharidi have one son, Haeden, and are expecting a second child in November.

Please make Tom, Scharidi, and Haeden feel welcome. Tom can be contacted at (662) 325-2701, office; (662) 418-3031, cell; or by email at tbarber@pss.msstate.edu.

A Good Spring for Crabgrass

By Dr. Richard Watson

A warm, wet spring and early summer has favored the germination and establishment of crabgrass in many pastures and hay fields. While crabgrass is often considered no more than a weed in many situations, it can be a very valuable high quality component of pasture and provide some good grazing during the summer.

There are, in fact, several species of crabgrass in Mississippi. The most common are large or hairy crabgrass (Digitaria sanguinalis), and smooth crabgrass (D. ischaemum). Large crabgrass is the most common of these two and can be identified by its wide pale green leaves that are covered in coarse hairs. Smooth crabgrass can be differentiated from large crabgrass by its shorter, wider leaves and lack of hairs. Smooth crabgrass is generally of much less value as a forage species as yields are considerably lower than large crabgrass.

Crabgrass is an opportunistic species and readily volunteers where bare soil exists, such as after any spring cultivation or in patches where hay feeding or treading damage have occurred. There is generally plenty of seed in the soil so crabgrass can often be successfully established by lightly disking ground in late spring to allow these seeds to germinate.

Crabgrass is adapted to many different soil types and can tolerate a pH range of 5.5 to 7.5. However, crabgrass grows best on well-drained soils, such as sandy loam, sandy clay loam, or clay loam soils. Crabgrass, like most summer annuals, responds very well to nitrogen (N) fertilizer and yields of 10,000-12,000 lb/A can be achieved where N is not limiting plant growth. Monthly applications of 50 lb. N/A will support good crabgrass yields on most Mississippi soils.

When kept short (6-8"), crabgrass has good nutritional quality (14-16% crude protein, and 55-60% total digestible nutrients). Therefore, crabgrass pastures should be grazed when they are no more than 6-8" tall down to 3-4", and then rested for 14-21 days to allow regrowth.

While most of the crabgrass in the state is volunteer, there is a commercially available variety of crabgrass. "Red river" crabgrass was developed by R.L. Dalrymple at the Noble foundation in Oklahoma in 1988. This variety was selected from the wild population for greater yields.

Nutrient and Soil Management

By Dr. Larry Oldham

We are between spring sampling and fertilization and slowly beginning to think about fall sampling and applications as the current crop year unfolds. This month we will think about large scale soil nutrient issues as we look at the current crop for nutrient deficiencies and toxicities, and wonder whether this should have been the year we finally invested in lime.

According to the 1997 Census of Agriculture, Mississippi has 10.1 million acres in farms, of which 6 million are harvested cropland. About three quarters of the cropland is harvested as crops and about a fifth is used as pasture. Mississippi has a diversity of soils; several hundred series have been described. I have walked fields with clay at one end of the row and sand on the other.

Today's agricultural soils are the aftermath of intensive cropping for decades, even over a century in a few places. Some in Mississippi are among the most naturally productive agricultural soils in the world; others require knowledgeable fertility management to economically produce crops in an environmentally benign manner.

Not all Mississippi soil/crop systems require extensive or expensive fertilizer applications; however nutrient management can be a significant investment. Mississippians aggregately spent an average of $129,829,000 per year on fertilizer and lime purchases from 1997 to 2001 (Mississippi Agricultural Statistics Service). For row crops, fertilizer and lime material expense can be 7 to 11% of production costs (Mississippi State Agricultural Economics Department Crop Budgets).

Proper nutrient management is always based on soil testing. Public and commercial soil testing laboratories analyze soil samples for fertilizer and lime needs and provide soil fertility recommendations based on the results. Soil testing also aids diagnosis of poorly performing plant material.

Soil fertility recommendations can and do vary between labs based on the philosophy of the organization (maintenance, maintenance plus buildup, etc), and the research on which they are based. However, the goal of all lab recommendation systems should be to provide sound agronomic advice that is economical and environmentally conscious since soil fertility and management issues are integral to societal concerns regarding agriculture and water, air, and soil quality.

Soil related themes such as carbon sequestration, nutrient management, nutrient movement out of soil, heavy metal bioavailability, wind and water erosion, sedimentation, and tillage management are issues of national and international interest. Carbon in soils is now traded on a futures market in Chicago. Nutrient and soil management are covered in regulations from a number of agencies.

Soil management is closely tied to surface water quality. Control of sediment, nutrients, and pathogen movement in the landscape is beneficial both for the individual producer and society at large.

In by-product utilization, the answers once were to land apply any unwanted material, and the answer to pollution was dilution. Now we know pathways exist that can turn something that is benign in one setting, into something of great, passionate interest in another setting. Introduction of substances into the food chain is not a trivial consideration.

Soil is amazing; it provides food and fiber, it is the basis for our economic system, and it is constantly changing. We must appreciate this resource for its complexity and for our well-being.

As July ends, we will be harvesting. As the crops start coming in, look at what they are telling you, and develop or implement your nutrient management planning for the next crop cycle. If you are a producer using a consultant or commercial firm for soil testing, work with them on scheduling early for this fall! It helps with their planning and it helps tremendously with the sample flow through all laboratories.

Soybeans

By Dr. Alan Blaine

With the recent rains, I feel we need to focus primarily on 4 areas.

1. A large portion of this crop is extremely early; in fact, some of this crop is about two weeks from being at the R6 (complete seed fill) growth stage. This crop needs a little help but it might be a candidate for a late fungicide application.

There are basically three strategies to consider for fungicide applications. A late shot (R5-R6) for control of late season cercospora and/or seed quality, we basically have two options, Quadris or Topsin M. Quadris will not control cercospora. In fact, it might be considered a cercospora fertilizer. Seed quality can be achieved with Quadris at the 6.0 oz. rate, but we feel 4.0 oz. will do the job.

A well-timed application of Topsin M can give contol of both late season cercospora and provide seed quality benefits. However, if applied too early it might not have the staying power to help late season. Keep in mind cercospora has appeared to have gotten worse the last few years particularly on early-planted IV's. If you want to control cercospora do not wait too late.

Topsin M does have a generic counterpart called Thiophanate-methyl (TM 85). The rate for Topsin is .75 lb. of formulated product and .6 lb. for TM 85. The interest in the generic material is high because Topsin has been difficult to obtain in years past and I also understand there is a significant price difference. I wish all fungicides were affordable, but the cost is still such that my producers are not willing to make the investment.

2. Plantings after mid-April to mid-May have an excellent yield potential. If you feel you have a good crop and have not experienced any major problems, strongly consider a fungicide + Dimilin combination. We are not applying Dimilin to the early crop. However, our plans are to apply Quadris (4.0 oz. rate) + Dimilin (2 oz./acre) to beans planted in this window.

Applications to plantings later than this should be made based on yield potential, cropping history, and outlook for future weather.

Conditions over the last few weeks have the potential to greatly enhance disease development, but dry conditions in the next few weeks could halt development also. These decisions are not easy, but year after year if a fungicide application does not allow you to achieve a big increase in yield, the increase will be sufficient enough to pay for the application.

3. Some fields may need to be managed closely after rainfall slows. If it turns hot and dry some of this crop will wilt fairly fast. Shallow root systems may be a concern, but I doubt it is going to be a problem on a lot of this crop. At times, we see root systems abort under saturated conditions, but it usually occurs on smaller plants.

The biggest concern is getting water off of flooded fields. I am going to remain optimistic about many areas that saw water back up in fields for short durations. Additionally, when this flooding occurred, both water and ambient temperature were very beneficial.

4. Watch stinkbugs. We are expecting populations to build, but it has been erratic thus far. Do not take this pest for granted. Feeding on the earliest planted portion of this crop has proven to be more damaging than later plantings.

Get ready to harvest this crop. I feel our planter power far exceeds our ability to harvest as fast. This is the year we pull out all stops regarding efficient harvest. We need to help each other. I cannot emphasize enough; timely harvest. If your neighbor has acreage ready, help him so he can return the favor.

We must deliver a quality product. Sixty to seventy percent of this crop could make August delivery. We may be ready on our end, but even though they booked it on their end, dumping this crop might be where we encounter a bottleneck.

We have an early crop. Our neighboring states have committed some acreage, but not as much as Mississippi. In order to facilitate timely harvest be prepared to put some of this crop in bins. Whatever we do, let's get it out as quickly as possible.

Corn

By Dr. Erick Larson

Plentiful rain - The over abundant rainfall received during June has caused some problems that deserve some attention. Extended soil saturation may promote nitrogen loss through denitrification, particularly on heavy, clay soils. Denitrification occurs when nitrate nitrogen is converted into nitrogen gas by microorganisms and escapes into the air. Nitrogen deficiency is characterized by yellowing (and later dying) beginning at the leaf tip and progressing along the leaf midrib on lower corn or sorghum leaves. Although these conditions may cause nitrogen deficiency before the crop reaches maturity, the likelihood of crop yield response to supplemental nitrogen application is relatively remote since most of Mississippi's corn crop is approaching the latter reproductive growth stages. Also, the frequent rainfall has promoted leaf blight development in several fields. Scout your fields for irregular leaf lesions and submit plant samples to the MSU Plant Pathology Laboratory for identification. Leaf blight development may be more likely in fields previously planted in corn, because the disease organism overwinters on infected residue.

Will rainfall hurt pollination? - Corn possesses a vast overabundance of pollen and several traits, which make the pollination process relatively immune to overhead irrigation or rainfall disturbance. Corn produces a huge overabundance of pollen grains (more than 4000 pollen grains per silk). Physical disturbance caused by overhead irrigation occurs over a very short time period in relation to corn pollination capacity. Pollen shed normally lasts 5 to 8 days, during which pollination may occur at any time. Corn plants also have an innate ability to stop pollen shed when the tassel is too wet or dry and trigger pollen shed when conditions are favorable. Additionally, silks are quite sticky, which makes pollen grains hard to wash off after they land on a silk. Thus, the physical disturbance caused by overhead irrigation will not reduce corn pollination in a normal field/agricultural environment.

Irrigation termination - Despite plentiful rainfall received in June, there is a slight chance we may need to finish out the corn crop with supplemental irrigation, if it dries out in early July. A common irrigation error is terminating irrigation before physiological maturity (black layer) occurs. Although this crop is slightly earlier than normal, most corn will not likely reach physiological maturity until mid to late July -- depending upon the latitude and planting date. Premature irrigation termination will accelerate maturity, prohibiting kernels from reaching their full potential size and weight. Although kernels appear somewhat mature and corn water use begins declining at the dent stage, this is too early to terminate irrigation. Potential kernel weight is only about 75% complete at the dent stage. Thus, termination of irrigation at this stage can reduce grain yields as much as 15-20% when hot, dry conditions persist.

Check the milk-line - Corn producers can monitor kernel maturity for irrigation scheduling purposes by observing the progression of the milk-line between dent stage and black layer. The milk-line is the borderline between the bright, clear yellow color of the hard seed coat outside the hard starch layer, compared to the milky, dull yellow color of the soft seed coat adjacent the dough layer. To observe the milk line, break a corn ear in half and observe the cross-section of the top half of the ear (the flat side of kernels opposite the embryo). It generally takes about 20 days for the milk line to progress from the kernel tip, down to the base. Growers can use this guideline to estimate the approximate maturity date. For instance, if the milk-line is half-way down the kernels, it will take about another 10 days to reach physiological maturity. Thus, the field needs supplemental irrigation water to supply moisture for 10 more days.

Sorghum

By Dr. Erick Larson

Sorghum black layer-Grain sorghum physiological maturity is characterized by formation of a black layer similar to corn. However, the abscission layer is visible without scraping the seed coat. The sorghum black layer can be found at the kernel base opposite the embryo. Kernels at the top of the head mature first, followed by kernels at the base of the head. Seed weight accumulation is complete and moisture typically ranges from 25-35% when physiological maturity occurs. Herbicide harvest aid application or irrigation termination should not occur before the black layer signifies physiological maturity.

Rice

By Dr. Tim Walker

After having recently accepted the Extension Rice Specialist position, Mr. Nathan Buehring will be joining us at Stoneville effective July 16, 2004. Nathan is currently completing his Ph.D. at Mississippi State University. On behalf of the rice research faculty at Stoneville, I welcome Nathan to Stoneville.

The rice crop is continuing to progress. Rice that emerged between April 15 and April 22 should begin heading shortly after the fourth of July. I began rice research in 1998 and remember applying midseason fertilizer the first and second week of July. With the number of acres of Cocodrie and Clearfield 161, you should have already begun scouting for sheath blight. As I write, a limited number of fields have either received or will receive a fungicide application this week. As more acreage progresses past midseason, and weather conditions continue as we are experiencing right now, I expect to see disease increase.

There is a substantial amount of rice that is not as far along. We have a fair amount of acreage that has just been flooded or is nearing flooding. Keep a watch for midseason. Later planted rice does not remain vegetative as long as earlier planted rice. I have seen a number of fields where flooding was delayed because herbicides could not be applied, and by the time a flood was established, nodes were either stacking or beginning to separate.

Phosphorus deficiencies have been more numerous this year than in the past (Figure 1). I have been able to diagnose some of the fields early enough to apply phosphate into the flood. When I have caught the problem early, the affected areas began growing again, but those areas probably will not yield as well as unaffected areas or areas that were treated at or near planting. If you saw areas in your fields that seemed to quit growing once the flood was established, make a note of it and try to soil sample those areas this winter.

I was at a meeting held by Dr. James Smith in the spring and one of the topics dealt with drift. One of the featured points was to communicate with your neighbor so that both would know where herbicide sensitive crops would be planted. The reason hit home with me last week as I walked through a field of Cocodrie that was adjacent to a field of CL-161. Newpath drift on conventional rice is detrimental to the conventional rice (Figure 1). Communication will hopefully go a long way in preventing off-target herbicide drift.

Figure 1
Phosphorus deficient rice

Figure 2
Newpath drift onto Cocodrie rice

Figure 3
Closeup of Newpath drift onto conventional rice

Rainy Irrigation Season

By Jim Thomas

It seems as if it has rained the entire crop season thus far. If and when it does stop many producers are not going to be ready to start their irrigation systems. Growers have delayed putting out pipe or maybe even purchasing pipe to get ready for irrigation. Seems as if every time we get ready to start a soybean field we get a rain, and cotton has been the same way. Many growers have thought about irrigating some cotton but then get enough rain to put it off for another week or so. Crops so far have taken the wet conditions very well. The cloudy weather isn't helping anything but is keeping things from getting hot and dry to quickly. When the sun does come out, and it will, and the temperature goes up, and that will happen too, there will be a 10 day to 2-week window to get irrigation laid and started. With the size of the crop we have at this time, when the sun comes out it will be using maximum water. Irrigation delays from this time on will only cost in yield because everything is in the reproductive stage of growth. Fuel costs may discourage some growers from going ahead and putting irrigation out but remember, this crop has not hurt for water at all to this time and stress will certainly cause yield reductions if it comes in during the reproductive period since the plants are large and lush. Corn will probably be the first to start maturing along with some early season beans and if the rains continue we may not need to irrigate those crops anymore but odds are you will. Corn still needs good moisture at black layer, and soybeans should be terminated about a 7-10 days after the beans are touching in the pods 4 nodes down from the terminal.

At this time I would encourage growers to purchase their pipe and lay it out. They may not want to punch it yet but at the first opportunity they need to get ready. Hopefully all the irrigation engines are set or should be and systems are ready to run, if not they should be. When the sun does start shining and the heat moves in everything should be ready because all the crops will need water at the same time. Getting ready at the time the crop needs water will delay starting two to three days at least and cause yield reductions. Encourage growers to get ready and be ready because when the time comes it will be here quickly and many will not be ready to start their irrigation systems.

Dr. Michael Collins, Department Head
Department of Plant and Soil Sciences
Box 9555
Mississippi State, MS 39762
(662) 325-2701

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