Number 304 July 1, 2011

Transcription

1 Number 304 July 1, Alfalfa management under drought conditions 1 2. Crunch time for Kansas corn crop: The effect of high heat and drought 2 3. Reports of ergot in wheat 6 4. Annual Oklahoma-Kansas Canola Conferences planned 7 5. Comparative Vegetation Condition Report: June Alfalfa management under drought conditions Alfalfa has been under stress in many parts of Kansas during much of May and June. The ongoing drought in south central and southwest Kansas is causing stunted growth and loss of leaves. Some stands are beginning to bloom, but only have 8 to 12 inches of growth. This will affect management plans. Periods of drought after a cutting has a big effect on the number of stems that will be present at the subsequent harvest. The greater the drought stress, the lower the stem number. However, leaf growth is generally not as limited by periods of drough. The result is that plants will generally be shorter under drought stress, resulting in lower yields. But because of an increased leaf:stem ratio, quality can be relatively high. Normally, a second alfalfa cutting should be made at 1/10 th bloom, which coincides with the beginning of crown regrowth. But this year, producers may have to consider taking their second cutting of alfalfa with much less top growth than they d like because some of the second-cutting alfalfa is already in the bloom stage again. If plants are in the bloom stage, it is time to harvest. With the price of hay this year, it may be more economical than usual to harvest minimal tonnage hay. For alfalfa that is not blooming yet but is starting to drop its leaves, a producer should consider cutting early just to maintain the most nutritious part of the plant. If cutting is required before the optimum time, root reserves on newly-established stands or even older stands may not be satisfactory to permit rapid regrowth. But left uncut, the hay crop may be lost and damage to the stand may occur. If producers are forced by drought stress to make a cutting earlier than the ideal time, it s important to delay the next cutting enough to allow nutrient reserves in the roots to replenish. 1

2 The benefit of alfalfa as a forage is that it is one of our most drought-resistant crops, even though it may not seem like it now. It has a very extensive tap root which allows it to scavenge the soil profile for moisture. In addition, it has an inherent ability to go into prolonged dormancy during drought periods when there isn t enough water to produce leaves and stems. Once rains return, it should resume to normal growth. -- Doug Shoup, Southeast Area Crops and Soils Specialist dshoup@ksu.edu -- Jim Shroyer, Extension Agronomy State Leader jshroyer@ksu.edu 2. Crunch time for Kansas corn crop: The effect of high heat and drought It is crunch time for the Kansas corn crop. Dryland corn has been under drought and heat stress for anywhere from several days to several weeks in many parts of central and western Kansas, especially south of I-70. Subsoils are very dry, and it will take quite a bit of rain to bring these soils back to normal. High temperatures can cause problems in corn even when soil moisture is adequate -- and will compound problems in drought-stressed corn. Hot, dry conditions are particularly damaging during pollination (VT-tassel through R1-silk). Much of the corn crop in Kansas is just now entering this critical period for determining grain yield. Some fields are still in the late vegetative stage, struggling to exert a tassel. In some fields, the upper corn leaves have already turned brown and necrotic. Drought-stressed dryland corn in late June in Cowley County. Photo by Jill Zimmerman, Cowley County Research and Extension agent. 2

3 Drought-stressed dryland corn in late June in Harper County. Photo by Stu Duncan, K-State Research and Extension. Stressed dryland corn in Marion County, tasseling but with no silks, in late June. Photo by Stu Duncan, K- State Research and Extension. Corn in northwest Kansas is behind the rest of the state in development. Most corn in that region is anywhere from 2 to 5 feet tall. Soil moisture conditions are highly variable across northwest 3

4 Kansas. However, water use is increasing and drought stress is showing up on some corn fields during mid-day. In general, if a substantial rainfall does not occur in the area in the next few weeks, many fields may not make it far into the reproductive stage before the corn plants succumb to the dry conditions. Low-output wells on pivots will also have a difficult time meeting the water needs of irrigated corn. Drought-stressed corn on some irrigated pivots has the potential to be a common occurrence because of this situation. Effects of stress at pollination time There are several reasons why the four weeks centered around pollination are so critical for determining grain yield. During the last couple of weeks before tassels emerge, the potential ear length is being determined. Extreme stress at this time can reduce the number of kernels per row affecting potential ear size. Extremely high temperatures prior to and during pollen shed can reduce pollen viability. Drought stress can slow silk elongation so much that the pollen may be shed before the silks emerge. Even if pollination does occur successfully, kernels may abort during the first several days of development under severe heat/drought stress. All of these factors can reduce successful pollination, kernel set, and kernel development, reducing the number of kernels per acre the greatest determinant of grain yield. Management options for stressed corn Where dryland corn has been under severe drought stress, you ll have to decide whether to let it go and hope for some kind of grain yield, salvage the crop for silage or hay, or leave the crop in the field for its residue value. It likely will pay to wait until after pollination is complete before making this decision to get some idea of kernel set. If kernel set is good, the ears at least have the potential to produce grain. If kernel set is severely reduced, the first step is to estimate potential grain yield based on kernel numbers per acre and average to slightly below average kernel size. This can help you make the grain vs. forage decision. Economically, should you leave the corn or cut it for silage or hay, or leave it for residue? The value of the residue for moisture retention, soil quality, and future crop productivity will vary depending on the situation, and can be hard to quantify -- but it is considerable. As for the silage/hay vs. grain decision, if the yield potential is less than 25 bushels per acre, it s probably best to cut it for silage or hay. If the yield potential is 50 bushels or more, it s probably best to harvest it for grain. If the yield potential is between 25 and 50, the decision will depend on the price of corn, the quality of the silage, and on a producer s ability to use or sell the silage. Of the two options for dryland corn that has limited yield potential silage or hay -- silage is normally the preferred option. However, you need the facilities to make silage (or sell it to someone who does), and there must be enough moisture in the plants to properly ensile. And where there s no ear at all, silage may not be a good option. Where the ear is very small, or has poor seed set, the silage will have lower energy value (TDN) and lower overall forage quality than normal. Even at normal yield levels, silage quality begins to decline when grain yield drops below roughly 150 bushels per acre, and continues to decrease as grain yields keep going down. To cut corn for silage, you need 65 to 75 percent moisture in the plant. If plants are suffering from drought, they may have lost some of the bottom leaves. The top leaves may have browned 4

5 off or turned white. In that case, the plants probably do not have 65 percent moisture, depending on how much moisture is in the stalk. Where that s the case, your only option is probably to chop and graze, or hay the crop like a summer annual forage. The pasture/hay shortage that exists west of the Flint Hills and south of I- 70 may make haying the failing corn crop a more desirable option this year. When chopping or cutting for hay, stalks should be cut at least six to eight inches off the ground to avoid nitrates in drought-stressed corn. Under drought conditions, the plant does not grow normally and high levels of nitrate can accumulate, especially in the lower portions of the stalk. You should also have corn hay (or stubble if you plan to graze) tested for nitrates. A forage nitrate test costs only $5-15 and it s the only sure way to make sure the hay is okay to feed to cattle. Ensiling the corn, if possible, is preferred to chopping or grazing because of that potential for nitrate toxicity. If you plan to have cattle graze the corn field after it has been chopped or cut for hay or silage, watch for any shattercane or Johnsongrass that comes up after a rain. New regrowth from these sorghum-type plants after a drought can be dangerously high in prussic acid. How much silage can producers get from drought-stressed corn? A publication from the University of Wisconsin estimates that for corn that has been stressed, with limited grain yield potential, producers can expect about one ton of silage per acre for every five bushels of grain yield. For corn that is not stressed, producers can get about one ton of silage for each six to seven bushels of grain yield. If little or no grain is expected, a very, very rough pre-harvest estimate of yield can be made by assuming that one ton of silage can be obtained for each foot of plant height, excluding the tassel. Putting a value on silage or hay One of the biggest questions is how to put a value on the silage or hay. The price of corn silage is typically based on corn or hay prices. The K-State Farm Management Guide crop budgets value silage in the field at 8 times the price of corn, meaning that if corn is $6/bushel, the price of corn silage would be $48/ton ($6 x 8). However, drought-stressed corn typically will have a value of percent of normal corn silage, so a more appropriate rule of thumb for drought-stressed corn silage standing in the field would be 6 times the price of corn. Current projected costs for silage chopping, hauling, and silo filling range from $8.00 to $8.50/ton. Harvesting corn for grain is expected to cost $0.50 -$0.55 per bushel. Before any action is taken in regard to harvesting corn for grain, silage, or hay, producers should contact their crop insurance agent. -- Kraig Roozeboom, Row Crop Production and Cropping Systems Specialist kraig@ksu.edu -- Brian Olson, Northwest Area Crops and Soils Specialist bolson@ksu.edu -- Kent Martin, Southwest Area Crops and Soils Specialist kentlm@ksu.edu 5

6 -- Doug Shoup, Southeast Area Crops and Soils Specialist -- Stu Duncan, Northeast Area Crops and Soils Specialist -- Troy Dumler, Southwest Area Agricultural Economist 3. Reports of ergot in wheat There have been multiple reports of ergot in wheat this week coming from north central Kansas. To date the information suggests that ergot was detected in loads of grain in Jewell and Republic counties. The harvest is just getting started in this area and it is possible that more loads of grain will be found to be positive for this fungal disease. Ergot is a fungal disease that infects the wheat and other grasses during the flowering stages of growth. The fungus colonizes the developing wheat kernels, resulting in large dark-colored fungal survival structures called sclerotia. The fungus produces a toxin that can cause serious health problems for humans and animals. Loads of grain containing ergot may receive price discounts or even be rejected at the point of delivery. Wheat heads infected with ergot showing the dark colored sclerotia that have replaced the normal grain. Photo by O. Maloy, Washington State University. 6

7 The fungus that causes ergot can survive between growing seasons as a sclerotia. These sclerotia germinate in the spring, resulting in specialized spore-producing structures. The spores are then moved by wind to nearby wheat fields. The disease is favored by cool wet conditions during these critical growth stages, and it appears that the heavy rains in north central Kansas created conditions favorable for ergot to infection some late-flowering fields. Ergot is also able to infect many types of wild grasses and cereal crops including rye, barley, and wheat. Rye and barley are generally considered to be more susceptible to ergot than wheat. In fact, some of preliminary reports of ergot contamination are associated with fields that had a feral rye problem. This suggests that the rye may be contributing to the levels of ergot observed in some loads of wheat grain. The ergot sclerotia can be removed from grain with grain cleaning equipment. Cleaning large volumes of grain after harvest may be impractical, but it may be possible to remove many of the sclerotia by turning up the air on the combine during harvest. Grain from fields infested with ergot should not be saved for seed because of the risk of sowing the fungus along with the wheat. If it is necessary to save the grain for seed, it would be a good idea to have the grain cleaned to remove as many sclerotia as possible. Crop rotation is best means of avoiding future problems with ergot. Fields infested with ergot sclerotia should not be planted back to wheat this fall. The beneficial effect of crop rotation will be reduced, however, if feral rye and other grassy weeds are allowed to head within or around the affected fields. Mowing the grass in ditches surrounding the fields in question will reduce the risk that fungus could also survive in these areas. -- Erick De Wolf, Extension Plant Pathology dewolf1@ksu.edu 4. Annual Oklahoma-Kansas Canola Conferences planned Kansas State University, Oklahoma State University, and Cameron University will team up later this month to hold the Seventh Annual Oklahoma-Kansas Winter Canola Conferences. The July 19 conference will be held in the Hoover Building at the Garfield County Fairgrounds in Enid, Okla. The July 20 conference will be held in the Student Union of Cameron University in Lawton, Okla. Each conference, which is free and includes morning refreshments and a sponsored lunch, begins at 8 a.m. with registration, coffee, and doughnuts. Door prizes will be given away during each conference. The program begins at 8:20 a.m. Presentations and speakers include: Soil Preparation and Planting Mark Boyles, OSU. Winter Canola Varieties Chad Godsey, OSU and Mike Stamm, KSU. Insects, Diseases and Weeds Tom Royer, Sarah Donelson, Kris Giles, OSU entomologists; John Damicone, OSU plant pathologist; and Mark Boyles, OSU agronomist. Winfield Solutions and Answer Plot Update Jay Bjerke, Winfield Solutions and Croplan Genetics. 7

8 Johnston Enterprises Update Van Schuermann, W.B. Johnston Grain Co. Oklahoma Oilseed Commission and Great Plains Canola Association Updates Canola Crop Insurance Update Phil Hamilton, Risk Management Specialist, USDA-Risk Management Agency Fertilizing Canola Brian Arnall and Hailin Zhang, OSU soil scientists Economics of Wheat and Canola Rotations Eric DeVuyst and Francis Epplin, OSU agricultural economists Harvesting Options Heath Sanders, Producers Cooperative Oil Mill (PCOM), and Josh Bushong, OSU agronomist Grower Panel Discussion Josh Bushong, OSU agronomist (at Enid) and Todd Baughman, Texas A&M agronomist (at Lawton) In Enid only, the program and lunch will be followed by a meeting of the Oklahoma Oilseed Commission at 1 p.m., followed by a meeting of the Great Plains Canola Association at 2 p.m. -- Mike Stamm, Canola Breeder mjstamm@ksu.edu 5. Comparative Vegetation Condition Report: June 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. The maps below show the current vegetation conditions in Kansas, the Corn Belt, and the continental U.S, with comments from Mary Knapp, state climatologist: 8

9 Map 1. The Vegetation Condition Report for Kansas for June from K-State s Ecology and Agriculture Spatial Analysis Laboratory shows that the eastern third of the state has the most photosynthetic activity. Parts of the Flint Hills region are beginning to show lesser photosynthetic activity, as dry conditions in the region develop. 9

10 Map 2. Compared to the previous year at this time for Kansas, the current Vegetation Condition Report for June from K-State s Ecology and Agriculture Spatial Analysis Laboratory shows that the photosynthetic activity levels in the North Central and East Central divisions are about on par with last year. The western third of the state, as well as south central Kansas is much behind last year s productivity. Southeast Kansas is also beginning to show signs of reduced photosynthetic activity. 10

11 Map 3. Compared to the 22-year average at this time for Kansas, this year s Vegetation Condition Report for June from K-State s Ecology and Agriculture Spatial Analysis Laboratory shows that the northern and eastern portions of the state continue to be above average in photosynthetic activity. Despite some heavy rains in Hamilton and Greeley counties during mid June, photosynthetic activity in those areas has not improved dramatically. Only Cheyenne County in northwest Kansas is showing much above average photosynthetic activity. This is due to the milder temperatures as well as the rainfall. Temperatures in the Northwest division averaged only 1.1 degree F above normal, while in south central Kansas temperatures averaged 6.7 degrees warmer than normal. 11

12 Map 4. The Vegetation Condition Report for the Corn Belt for June from K-State s Ecology and Agriculture Spatial Analysis Laboratory shows as soils dry out in Iowa, Illinois, and Indiana the level of photosynthetic activity has increased. Parts of southern Minnesota and the Boot Heel of Missouri, as well as along the Red River in North Dakota, continue to experience flooding. This has continued to limit photosynthetic activity in these regions. 12

13 Map 5. The comparison to last year in the Corn Belt for the period June from K-State s Ecology and Agriculture Spatial Analysis Laboratory shows that the delayed plantings and saturated soils in the northern and eastern portions have reduced photosynthetic activity. Corn fields in Indiana are reported to be very uneven, due to saturated soils and nitrogen deficiencies. 13

14 Map 6. Compared to the 22-year average at this time for the Corn Belt, this year s Vegetation Condition Report for June from K-State s Ecology and Agriculture Spatial Analysis Laboratory shows above average photosynthetic activity in western South Dakota and the Nebraska Panhandle. This is the dividing line on the moisture and favorable temperatures. North and east of the region, cooler-than-average temperatures and wet soils have reduced activity. South and west of the region, high temperatures and dry conditions have also limited photosynthetic activity. Temperatures in south central Kansas average 6.7 degrees warmer than normal, while temperatures in Indiana averaged between 2 and 5 degrees cooler than normal. 14

15 Map 7. The Vegetation Condition Report for the U.S. for June from K-State s Ecology and Agriculture Spatial Analysis Laboratory shows that the last half of June had very active biomass production in the eastern half of the country. The mountains of Colorado are also seeing active vegetative production, as the snowpack recedes. 15

16 Map 8. The U.S. comparison to last year at this time for the period June from K-State s Ecology and Agriculture Spatial Analysis Laboratory shows parts of Montana and western Oregon and Washington have a greater level of photosynthetic activity. Winter moisture in these regions was favorable, and temperatures have also been favorable. The eastern and northern U.S. has been plagued by excessive moisture and cool temperatures, while the central and southern U.S. has had below-normal precipitation and warmer-than-normal temperatures. Both patterns have limited photosynthetic activity in the regions. 16

17 Map 9. The U.S. comparison to the 22-year average for the period June from K-State s Ecology and Agriculture Spatial Analysis Laboratory shows the drought continues to severely limit photosynthetic activity in the Southern and Western Plains, where photosynthetic activity is much below the long-term average. The cool temperatures and saturated soils have also resulted in below-average productivity in the Upper Midwest and Ohio River Valley areas. As the record snow pack in Idaho, Montana, and Wyoming recede, photosynthetic activity in these areas is running higher than the long-term average. Note to readers: The maps above represent a subset of the maps available from the EASAL group. If you d like digital copies of the entire map series please contact us 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. -- 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, or Jim Shroyer, Research and Extension Crop Production Specialist and State Extension Agronomy Leader jshroyer@ksu.edu 17