Stressed wheat is generally showing some combination of the following symptoms:

Transcription

1 Number 349 May 11, Causes of wheat stress in western and central Kansas 1 2. Evaluating corn early-season growth 3 3. Sorghum planting management 7 4. Comparative Vegetation Condition Report: April 24 May Causes of wheat stress in western and central Kansas Wheat is under stress in much of western Kansas south of I-70 and west of Pratt and Great Bend. In areas east of U.S. Highway 281, there are also areas where wheat is under stress, especially on terrace tops. Stressed wheat is generally showing some combination of the following symptoms: * White heads, which developed very quickly over a wide area * Curled and dried up flag leaf * Tillers that have sloughed * Loss of one or more small developing kernels in the spikelet * Poorly developing kernels * Chlorotic leaves due to poor root development and nutrient deficiencies The stress this year came on quickly. There were general rains earlier in the spring, and topsoil moisture was adequate in most areas until recently. But where subsoils were very dry after last summer s drought, the wheat needed a regular supply of rainfall events this spring to support the topgrowth. Where that didn t happen, the wheat quickly became stressed, especially during the periods of extreme heat this spring the latest being May 4-5. Heading and grain fill is a period of high moisture use, with wheat using about 0.25 to 0.30 inches of moisture per day. If the moisture isn t available, the wheat will begin to show the symptoms listed above. The combination of dry soils and heat, in particular, will cause heads to turn white rather quickly, almost overnight. Any additional stress, such as diseases or insects, will just add to the stress. Cool weather has returned, but the crop still needs another rain or two where it is dry. If rain comes to stressed wheat while the kernels are still in the milk stage of development or earlier, the wheat may be able to recover some yield and test weight potential as long as the flag leaves are still alive. If the plants are under severe stress and shut down while kernels are in the early dough stage, it is unlikely that any subsequent rain will help the kernels complete their fill. This will 1

2 result in a loss of yield and low test weight regardless of the weather during the remainder of the season. Stressed wheat on terrace tops in Saline County, May 8, Photo by Tom Maxwell, K-State Research and Extension Central Kansas District Agent. Wheat under stress in Barton County, May 8, This stress is throughout the field. Photo by Jim Shroyer, K-State Research and Extension. 2

3 Kernels from the field above. These kernels are in the milk stage, and have stopped developing due to heat and drought stress, and the death of the flag leaves. This will result in reduced yields and low test weight. Photo by Jim Shroyer, K- State Research and Extension. -- Jim Shroyer, Extension Agronomy State Leader 2. Evaluating corn early-season growth Getting a good stand of corn, with vigorous early-season growth, is the first step in getting good yields. When adverse conditions, such as a hard rain or unusually cool weather, occur after planting and emergence, producers should get out in their fields and take a close look at how their corn is doing. If the plants emerged in good fashion, but the seedlings then have problems maintaining adequate growth and development or leaf color, there may be several possible reasons. A few of the most likely causes include: Unusually cool temperatures, compacted soil, or waterlogging. Wet soils and unusually cool temperatures can inhibit root growth especially, slowing plant development. This can cause yellowed, wilting plants due to poor root growth, drowning, or a seedling blight infection. Seedling blight is often characterized by stem tissue near ground level that is discolored or water-soaked in appearance. Also, planting in wet soil can compact the seed furrow, inhibiting root growth. A shallow compaction layer can slow early root growth, resulting in stunted, nutrient deficient plants. 3

4 Sidewall and seed zone compaction in heavy clay soil. Photo by Stu Duncan, K-State Research and Extension. Early-season lodging ( floppy corn syndrome ). This is usually associated with hot, dry weather during V1 to V6, which prevents adequate development and penetration of nodal roots. Plants can survive for a time on just the seminal root system, but they will have little mechanical support. Reasons for poor nodal root development and an elevated crown include sidewall compaction, erosion after emergence but before nodal root development, and sinking of the seedbed due to pounding rains. Often a good soaking rain is enough to allow nodal roots to establish and plants to recover. Inter-row cultivation can be used to push soil against plants with exposed crowns. Floppy corn syndrome. Corn seedling lodging caused by dry weather and warm soil stunting crown root development. Photo by Doug Shoup, K-State Research and Extension. White grubs or wireworms. These soil insects may be eating the roots, which will cause the plants to wilt. Black cutworms. These insects, which can be found in the soil or on the surface, cause window paning of the leaves on young plants. Cutworms may also cut off seedling plants at the soil surface. Flea beetles. These tiny leaf-chewing insects can cause scratches on leaves. Eventually, the leaves may shrivel, turn gray, and die. Plants are more susceptible to flea beetle injury when temperatures are cold and seedling growth is slow. Seedling plants are often able to recover from flea beetle injury because the growing point remains below ground level until the fifth leaf emerges. 4

5 Poor growth that occurs as circular to oval patches in the field could be an indicator of nematode problems. Approximately 35 days after emergence is an ideal time to sample for nematodes, particularly the root lesion nematode that inhabits about 80 percent of Kansas corn fields. Take 20 cores at a depth of 12 inches from directly in or alongside the row from the outer edges of affected areas. Additionally, 2 to 3 root balls of affected plants should be submitted at the same time. Bag the root samples separately from the soil cores. Samples can be submitted through local Extension offices or sent directly to the Plant Disease Diagnostic Lab in Throckmorton Hall. Free ammonia from an anhydrous ammonia application. This can injure roots and kill germinating seed if ammonia was applied too shallowly (especially in coarser soils), too close to time of planting, or if dry soil conditions slowed the conversion of ammonia to ammonium. One way to minimize damage is to apply the ammonia at a 10 to 15 degree angle from the direction of planting. If injury occurs then it is more randomly distributed, reducing the multi-plant skips, and allowing the unaffected plants to compensate. Ammonia injury can also occur when sidedressing anhydrous ammonia under dry soil conditions. Root injury can occur if the plants get too big or the knives run too close to the row. Ammonia injury resulting from poor soil sealing can cause leaves to appear watersoaked or have dead margins. Roots may appear sheared off, or burned off. Plants will normally recover from this injury, but yields can be reduced. Putting a urea-based N fertilizer in contact with the seed. Urea will hydrolyze into ammonia and injure the seedling. Seedlings damaged after starter fertilizer containing urea-n was placed in direct seed contact. Photos by Dorivar Ruiz Diaz, K-State Research and Extension. Nitrogen (N) deficiency. This does not usually occur until a later stage of growth in conventional tillage systems. But in no-till corn, especially in high residue situations, N deficiency is common where producers haven t applied nitrogen as a starter, or broadcast a significant amount of N prior to or at planting. In early planting in very cold soils where no N was applied close to the seed as a starter, seedlings may be N deficient in conventional-till also. Nitrogen deficient corn seedlings will be spindly, with pale yellow- 5

6 green foliage. As the plants grow, the lower leaves will fire, with yellowing starting from the tip of the leaf and progressing back toward the stalk. Phosphorus deficiency. This can result in stunted growth and purple leaves early in the growing season. Phosphorus deficiency is often enhanced by cool, wet growing conditions. Iron deficiency. This can cause upper leaves to be pale green between the veins. Iron deficiency is more common on high ph and calcareous soils. Sulfur deficiency. This can result in stunted plants having pale green leaves, with no distinct pattern on the leaves. Herbicide injury. This is not as common now as in the past, but can still occur. Corn is very susceptible to injury from carryover sulfonylurea herbicides which may have been applied to a previous crop, such as wheat. Carryover depends on soil ph, soil texture, application rates, rainfall, and other factors listed on the herbicide labels. Symptoms include stunting, chlorosis, and an overall sickly appearance. Corn will not grow out of this type of injury. ALS herbicide carryover injury to corn. Photos by Stu Duncan, K-State Research and Extension. For more details, see Diagnosing Corn Production Problems in Kansas, K-State publication S- 54, at: Also, see Corn Production Handbook, K-State publication C-560, at: -- Kraig Roozeboom, Cropping Systems and Crop Production Specialist kraig@ksu.edu -- Dorivar Ruiz Diaz, Nutrient Management Specialist ruizdiaz@ksu.edu -- Jeff Whitworth, Extension Entomology jwhitwor@ksu.edu -- Doug Jardine, Extension Plant Pathology jardine@ksu.edu -- Stu Duncan, Northeast Area Crops and Soils Specialist sduncan@ksu.edu 6

7 -- Doug Shoup, Southeast Area Crops and Soils Specialist 3. Sorghum planting management A series of experiments funded by the Kansas Grain Sorghum Commission examined the interactions between grain sorghum planting date, hybrid maturity, and row spacing across a range of production environments. Two hybrids (one medium early and one medium late) were planted at two planting dates (typically early to mid-may and early to mid-june) in two row spacings (10-in. and 30-in.) at four seeding rates (20k, 50k, 80k, and 110,000 seeds per acre). These experiments were conducted at four locations in central and eastern Kansas over a period of four years. A total of 12 experiments were completed from 2008 through Three of the four years had growing season precipitation that was at or above normal at most locations. In 2011, precipitation was well below normal for all experiments. Does plant population need to be adjusted for different planting dates, hybrid maturities, or row spacings? Yield results indicated that the biggest factor to watch when deciding on seeding rate was planting date. Early planting tended to be less responsive to changes in plant population (Fig. 1). However, with June planting, plant populations needed to be at or even greater than typical recommendations to maximize yields. Sorghum plants tend to tiller less readily at warmer temperatures, so it is essential to have adequate stands with later plantings. Increasing the population in narrow rows resulted in greater yields in only one of the 12 experiments. Figure 1. Average yields from the four experiments where response to plant population differed with planting date. More plants often are needed with later planting to maximize yield. Is there a yield advantage to narrow rows? Under what conditions? Yields in 10-inch rows either equaled or exceeded yields in 30-inch rows in all 12 experiments. This included yield environments that ranged from 50 to 60 bushels per acre at Manhattan in 2011 to yields greater than 150 bushels per acre in 2009 at Belleville. When there was a yield advantage for narrow rows, it added 3 to 25 bushels per acre depending on year and location. 7

8 The exception to this yield advantage with narrow rows occurred in 2011 at Hutchinson under extreme drought conditions at the highest plant populations. Other experiments have documented yield reductions in narrow rows when drought conditions occur during grain fill. Does the response to row spacing depend on hybrid maturity or planting date? The most common factor affecting yield response to row spacing was planting date, with narrow rows occasionally having a greater advantage with later planting. Although this occurred only twice in the 10 experiments with different planting dates in this study, previous work has demonstrated a similar interaction of row spacing with planting date. Narrow rows may compensate in part for the reduced tillering associated with later planting by shortening the time to canopy closure. One indicator to watch over time is the number of heads per plant. The number of heads per plant decreased as the number of plants per acre increased (Fig. 2), tending to level off at close to one head per plant at populations greater than 50,000 plants per acre. In the relatively productive environments of 2008 to 2010, yield was maximized when the sorghum plants produced between 1 and 1.4 heads per plant -- in other words, when less than half of the plants produced a second productive head. Increasing the number of plants can result in only one head per plant, but can sap water supplies early in the season, reducing head size and yield. In the drought conditions of 2011, yields were maximized with more than two heads per plant because the lowest populations produced the greatest yield. With this season already shaping up to be dry, it may be a good idea to aim for the lower end of the recommended seeding rate. If conditions improve, sorghum has the ability to adjust tiller number, head size, and seed size to produce a yield that takes advantage of available resources. Figure 2. Number of plants per acre affects the number of heads per plant. -- Kraig Roozeboom, Cropping Systems and Crop Production Specialist kraig@ksu.edu -- Bill Heer, South Central Experiment Field bheer@ksu.edu -- Randall Nelson, North Central Experiment Field jrnelson@ksu.edu -- John Holman, Southwest Research-Extension Center jholman@ksu.edu 8

9 4. Comparative Vegetation Condition Report: April 24 May 7 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: 9

10 Map 1. The Vegetation Condition Report for Kansas for April 24 May 7 from K-State s Ecology and Agriculture Spatial Analysis Laboratory shows that high NDVI values have moderated. Western Kansas continues to be on the lower side of the scale, as does northeast Kansas, where corn emergence was beginning during this two-week composite period. 10

11 Map 2. Compared to the previous year at this time for Kansas, the current Vegetation Condition Report for April 24 May 7 from K-State s Ecology and Agriculture Spatial Analysis Laboratory shows that most of the state has higher photosynthetic activity. Some exceptions can be seen in northeast and north central Kansas, which tended to be wetter last year. 11

12 Map 3. Compared to the 23-year average at this time for Kansas, this year s Vegetation Condition Report for April 24 May 7 from K-State s Ecology and Agriculture Spatial Analysis Laboratory shows a continued pattern of higher-than-average NDVI values. The departure from the 23-year average is not as great as it was in last week s composite images. As the wheat crop remains ahead of average, photosynthetic activity in the wheat areas will continue to decrease. 12

13 Map 4. The Vegetation Condition Report for the Corn Belt for April 24 May 7 from K-State s Ecology and Agriculture Spatial Analysis Laboratory shows that the level of photosynthetic activity remains lower in the northern and western portions of the region as spring planting progresses. Illinois is an excellent example of this. In northern Illinois, corn planting is 73% complete with 31% emerged, whereas in southern Illinois corn planting is 94% complete and 74% emerged. 13

14 Map 5. The comparison to last year in the Corn Belt for the period April 24 May 7 from K-State s Ecology and Agriculture Spatial Analysis Laboratory shows that NDVI values tend to be at or above last year s levels at this time. Northern Illinois is the center for lower biomass production, while southeast Minnesota is ahead of last year. 14

15 Map 6. Compared to the 23-year average at this time for the Corn Belt, this year s Vegetation Condition Report for April 24 May 7 from K-State s Ecology and Agriculture Spatial Analysis Laboratory shows an area of lower-than-average NDVI values in Illinois. Crop progress in this area is ahead of normal, so the lower-thanaverage reading likely is the result of cloud contamination during this two-week composite period. In the area from the Bootheel of Missouri to southwest Indiana and western Kentucky, the lower-than-average NDVI values are a reflection of the ongoing drought conditions. Abnormal dry to moderate drought conditions are reported in this area. 15

16 Map 7. The Vegetation Condition Report for the U.S. for April 24 May 7 from K-State s Ecology and Agriculture Spatial Analysis Laboratory shows that generally high photosynthetic activity can be seen in the eastern U.S. and along the West Coast. Low NDVI values in northern and central Illinois are the result of lingering cloud cover in the region during this two-week composite period. Low NDVI values in southern Missouri and along the mid-mississippi River Valley are due to drier conditions in these areas. 16

17 Map 8. The U.S. comparison to last year at this time for the period April 24 May 7 from K-State s Ecology and Agriculture Spatial Analysis Laboratory shows the earlier retreat of the Mountain snowpack this year. Current snow cover in the Northern Rockies is at 44 percent, while last year s snow cover was at 60 percent during the same period. 17

18 Map 9. The U.S. comparison to the 23-year average for the period April 24 May 7 from K-State s Ecology and Agriculture Spatial Analysis Laboratory shows photosynthetic activity to be above normal. The Southeast is at near normal conditions, despite the intense drought in the region. Low NDVI values in Illinois and North Texas are due more to persistent cloud cover in these areas during this two-week composite period than poor vegetative conditions. 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 18 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