It has been three weeks since we had our last rain in SW Nebraska and we are seeing all dryland crops showing signs of drought. Reference evapotranspiration (ET) in the Upper Republican NRD ranged from 1.6 inches in Perkins Co to 2.9 inches in SW Dundy Co. This means that crops in SW Dundy Co used about 1.5 inches of water more than in Perkins Co. See image for more details on ET and rain data as well as crop growth stages and their water use coefficients for this period.
According to US Drought monitor none of the Counties in SW Nebraska are in abnormal drought, which can means that these conditions are (believe it or not) normal in SW Nebraska this time of the year. According to 30-year weather data, average August precipitation and ET are 2.50 and 9 inches, respectively. This means that the area had the August weather conditions in very close proximity to long term average.
We had very good growing conditions in May, June, July and August, so crops used all that water and heat to produce large biomass and increase yield potential. Rain is much needed to keep up with high water demands during the grain filling period in September, otherwise we will have to be satisfied with the mediocre dryland yields at the end of the year.
Reference evapotranspiration (ET) and rain in the Upper Republican NRD was around 1.3 and 0.05 inches, respectively. See attached image for more details on ET and rain data as well as crop growth stages and their water use coefficients for this period.
Dryland crops in SW Nebraska are showing signs of drought, but are generally in good conditions. My rough estimation on average dryland corn yield this year would be around 110 bu/ac. Irrigated corn and soybean look very good! Relatively lower ET allowed irrigators to catch up with crop water demand. A number of corn fields have high infestations of western bean cutworm with larvae already feeding on ears. Insecticide treatments are not advisable at this point since pest is well protected. If corn is to be planted next year consider Bt-trait that will control (or suppress it) or plan on insecticide application during the season. Western corn rootworm beetles are flying and insecticide application may be applied to prevent battles from laying eggs and reduce next year’s larvae damage. If corn is rotated with some other crop insecticide application is not recommended at this point.
Management checklist for wheat producers:
1. Control volunteer wheat and weeds in wheat stubble and fallow to preserve moisture and nutrients, reduce the weed seed bank and control disease vectors.
Research from USDA‐ARS, Central Great Plains Research Station in Akron indicates 4-6 bu/ac yield penalty on wheat for each inch of available soil water being reduced at wheat planting.
Nutrients taken up by weeds and volunteer wheat can increase the cost of your fertilizer inputs. Simple calculation for estimating your wheat fertilizer needs based on fertilizer and wheat price, residual soil nutrients and yield goal can be found at UNL Extension website.
Wheat Streak Mosaic Virus (WSMV) disease is transmitted by the wheat curl mite (WCM) and “green bridge” provides host plants for both virus and mite to survive and cause problems next year. Mace is wheat variety tolerant to WSMV and you should consider it if you had a history of WSMV in your field.
Recommendation: Tank-mixtures of glyphosate with 2,4-D or dicamba, or gramoxsone are usually very effective in controlling “green bridge”. Two applications might be necessary in some cases, but avoid applying these chemicals 2 weeks prior to planting to avoid herbicide injury.
2. Consider buying certified, fungicide-treated seed to prevent yield losses from seed- and soil-borne pathogens and eliminate germination and survival problems that may be associated with planting bin-run seed.
Lover test weights were reported this year from a number of producers that did not sprayed for stripe rust. Wheat leaves that were severely infested with stripe rust fell off prematurely and imposed a stress on wheat crop during the grain filling period. K-state researchers found that planting seed with lower than 55 lbs per bushel may require special attention such as shallower seeding depth, higher seeding rate, adjusting seed blower to blow out “chaffy” seeds, and germination test. For more information click here.
Seed-borne diseases including Black Chaff, Fusarium head scab and ergot observed in this year’s wheat crop. Soil-borne diseases including root, crown and foot rots are common if soil conditions are wet during germination period and yield losses can occur due to poor establishment. Click here for more information.
Recommendation: Plant certified, fungicide treated seed. If using bin-run seed send seed to a lab for germination test or do the germination test yourself by wrapping seeds in wet paper towel for 5-7 days and estimating percent that survived. If germination rates are less than 80% fungicide treatments are highly advisable. For list of fungicide seed treatments click here.
3. Variety selection is critical part of every cropping systems. This doesn’t necessarily mean to select highest yielding variety from the book and expect highest wheat yield in the county. We need to become more familiar with other characteristics such as winter hardiness, disease tolerance, maturity, etc. For example, Byrd is one of the highest yielding varieties commonly planted in SW Nebraska, but it is very susceptible to stripe rust; therefore, you need to be tracking progression of stripe rust throughout the season and be ready to spray preventively. This year $20/ac investment on spraying stripe rust on Byrd made approximately 30 bu/ac yield difference. For Nebraska Extension Fall Seed Guide click here.
Reference evapotranspiration (ET) in the Upper Republican NRD ranged from 4.18 to 5.24 inches in this 17 days period (from 0.25 to 0.31 inches/day), with area to the south and with less rain having larger ET. Two storm came through SW Nebraska on August 5th and August 8th, each carrying from 0.5 to 3.0 inches. Rain really helped all dryland crops as it came at the right time and after good growing conditions we had in June and July. Hopefully the trend will continue to produce outstanding dryland yields for this area.
To more accurately estimate rain and crop water use on your farm, look at the map (attached) provided, obtain weekly reference ET value from location closest to you and multiply that value by crop coefficient provided in the table.
Reference evapotranspiration (ET) in the Upper Republican NRD ranged from 1.70 inches at north parts of Perkins County to 2.20 inches in south Dundy County; we received between 0 and 1.70 inches in rain. To more accurately estimate rain and crop water use on your farm, look at the map provided, obtain weekly reference ET value from location closest to you and multiply that value by crop coefficient provided in the table.
Weeds control in wheat stubble
Time to control weeds in the wheat stubble! New Cropping systems specialist from Panhandle Research and Extension center, Cody Creech, suggested 3 steps to control weeds in wheat stubble: (1) Carefully identify weeds that are present in your field, (2) spray weeds kochia, Palmer pigweed, pricly lettuce, Russian thistle and other tough to control summer annuals with tank-mix of glyphosate, dicamba and/or 2,4-D to prevent seed development (3) monitor for winter annual weeds like rye, marestail and cheetgrass and plan timely herbicide application in fall and early spring. For more information click here.
Corn is at reproductive growth stage. Adults of Western Bean Cutworm have been emerging in past week and spraying has been done in the area. UNL’s recommended threshold for insecticide application is 5-8% of corn plants have egg masses and/or small larvae.
Sunflowers are at V5 to butonization stage. Field peas harvest is done. Soybeans are at R2-R4 growth stage (setting pods). Milo is at booth stage. Potatoes in tuberization stage. Dry beans are at 80%-full cover. Sugarbeets are at full cover.
Isolated t-storms delivered from 0.2 to 1.8 inches across Upper Republican NRD. Reference evapotranspiration (ET) losses were 2.0 inches on average. To estimate crop water use on your farm look obtain weekly reference ET value from location closest to you and multiply that value by crop coefficient provided in the table.
Wheat harvest is 95% done! Dryland yields range from 20 bu/ac to 90 bu/ac. Farmers that had hard winter kill and didn’t spray wheat for stripe rust had lover yield and lower test weight (about 53-55 lbs/bu). Wheat kernels diseased with ergot and/or Fusarium head scab have been observed. Although these did not appear to be a major yield limiting factor wheat can affect marketability of wheat seed. Loads can be rejected at the elevator if 0.05% of wheat kernels have ergot (about 0.5 oz/bu) or if over 1 ppm concentration of DON toxin has been detected in Fusarium-damaged kernels. Setting up your combine to blow out “chaffy” seed take care of this problem.
Corn is at V14 to tasseling growth stage. Adults of Western Bean Cutworm have been emerging in past week. If 5-8% of corn plants have egg masses and/or small larvae, consider an insecticide application either through a center pivot irrigation system of by airplane. It may be beneficial to select an insecticide that controls both spider mites and Western Bean Cutworm as mite populations are increasing in the area. Resistance of Western Bean Cutworm to proteins expressed in transgenic corn has been observed in SW Nebraska. Only the Bt corn hybrids containing Cry1Ftoxin (e.g. Herculex I, Herculex XTRA, SmartStax) are effective in controlling the pest. For more information on Western Bean Cutworm and its management click here.
Field peas harvest is in progress; dryland yields of 40 bu/ac have been reported. Soybeans are at R1-R3 growth stage. Milo from V8 to booth. Potatoes are in tuberization stage. Dry beans are at 50-80% cover. Sugarbeets are at full cover.
To estimate crop water use or crop ETc look at the map provided, obtain weekly ET value from location closest to your farm and multiply that value by crop coefficient provided in the table. Assuming your soil has enough moisture on the supply side this is how much water your crop used in a past week (June 29 to July 6). Reference ET values have been around 2.15 inches.