Crop water use June 22- June 29

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 22 to June 29). Reference ET values were around 2.00 inches and similar among 15 locations in Perkins, Chase and Dundy Counties.

Et and rain 6-29

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Schedule your irrigation based on crop water use

Nebraska Ag Water Management Network (NAWMN) is a collaborative group of farmers, crop consultants, NRD personnel and UNL Extension Educators that work together across the state of Nebraska to adopt water and energy conservation practices.

This is done by using simple WATER BUDGET equation. To keep up with WATER DEMAND (crop water use) we need to receive equivalent amount of moisture on WATER SUPPLY side of the equation, which includes soil available moisture, rain, and ultimately irrigation. Unfortunately, we can only control irrigation component of this equation. In the following paragraphs I will discuss how we can use newer technologies how to make every inch of water applied through irrigation to produce yield.

June 15 to June 21

This summer SW Nebraska adds about 15 locations collaborators (farmers and crop consultants) from Perkins, Chase and Dundy Counties to more accurately estimate WATER DEMAND (crop water use). Map of potential evapotranspiration (ETo) will be posted weekly in your newspaper, on radio, water.unl.edu website, on this blog, or twitter @agwithstrahinja. To estimate crop water use or crop ETc look at the map provided, obtain weekly ET value from location closes 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.

To accurately estimate WATER SUPPLY, first you need to know how much rain you received in the past week. Along with ET values we also provide rain data. However, keep in mind that rain can very much more from one place to other then ET.

Second, you need to know water holding capacity of your soil. For example, silt loam soil can hold 2.2 inches/ft while loamy sand can only hold 1.1 inches/ft. Research showed that plants start to loose yield due to water stress after soil water is more than 50% depleted. Therefore, in silt loam soil you have about 1.1 inches/ft more to manage then in loamy sand (4.4 inches if 4 foot profile). Chart with waterholding capacities of different soil type and trigger levels for irrigation can be downloaded here.

Second, you need to know how much water you have in your soil, and soil moisture sensors can help you with that. UNL did research that enabled us to use readings from Watermark sensors (in cb) and convert to inches/foot. Watermark sensors are very affordable (about $35 each) and accurate, and over years we learn to trust them. More about using Watermark sensors click here.

Example for irrigation scheduling based on ETc. Last week corn started with soil at field capacity and now is at V8 growth stage and it used 0.7 inches of water based on weekly reference ETo (1.5 inches) x crop coefficient Kc for V8 corn (0.5). Corn is grown on loamy sand that has waterholding capacity of 1.2 inches/foot, and at this time corn rooting depth is 2 foot. We want to keep our soil above 50% depletion to avoid water stress; thus, we have 1.2 inches in top 2 foot to manage (0.6 inches/foot x 2 foot). There was no rain last week, so there is 0.5 inches left in soil profile (1.2 inches/soil profile – 0.7 inches for ETc). In hot summer day corn at V8-V10 stage can easily take up 0.5 inches in 2 days; therefore, in this scenario (assuming there is no water allocation) irrigation is recommended to avoid water stress.

Crop report June 18

Weather conditions

About 1 to 1.5 of precipitation has been received in past week. Nitrogen leaching is a concern! About 50-70 lbs/ac of nitrogen has been found in 3rd and 4th foot of soil profile that is probably not going to be taken up by the crop. Taking a soil test is recommended to determine how much nitrogen has been lost and make corrections on your in-season nitrogen management plan.

Hail damage causing yield loss due to stand reduction

Storm carrying 1 inch of precipitation and pea size hail came across areas of Perkins and Chase on June 16. Assess hail damage to the crop before making replant decisions.

Corn plants without damaged growing point will recover with minor yield losses. In corn, growing point is under the soil surface until V5 to V6 stage; thus, protected from hail injury. If you have corn at >V5 knife to inspect the condition of growing point to accurately determine stand reduction.

Soybean has growing point at the tip of the plant, therefore small (V1-V3) soybean plants will not be able to recover after hail damage if growing point is damaged. Larger soybeans may be able to continue growing from semi-dormant axillary buds located inside the leaf axils at first 2 nodes when top of the main stem is cut-off.

Check UNL charts for determining yield loss due to stand reduction for corn, soybean and sorghum.

Wheat

Wheat kernel at watery consistency
Wheat kernel at watery consistency

Wheat started filling grain. Kernels are in between watery consistency to milky ripe. With moisture and we had in past month it has been a paradise for spread of diseases, especially in dryland corners that didn’t received fungicide treatment. Leaves are often covered less than 50% with green healthy tissue. Good news are that this year we had enough moisture to make 100 bu dryland wheat (if rain patterns continue), which will overweight some yield loss coming from diseases and hopefully bring it to above long-term average.

Other crops

Corn growth stages range from emergence to V7. Milo from emergence to V4. Soybeans planting is 90% done and V2-V3 soybeans are found in the area. Field peas and flowering and grew about a foot in past week, potatoes are also flowering and in excellent condition, sugarbeets are at 50% cover.

Sugarbeets at 50% cover
Sugarbeets at 50% cover
Soybean at V2
Soybean at V2

Crop report June 10

Srpayer stuck in the muddy field
Sprayer stuck in the muddy field

Weather conditions

Less than 0.5 inch of precipitation in past 7 days have dried fields enough for farmers to continue planting and spraying weeds. Assess wetness of your field carefully!!! Planting in wet soils can cause severe crusting and problems with crop emergence, especially in soybean. Avoid spraying wet areas with heavy equipment. Mark them with flag and spot-spray with ATV  sprayer.

Water management

Irrigating wheat is recommended to keep up with the water demand. On the 85-90 F days we had on 06-09-2015 wheat uses 0.37 inches per day, which is 2.59 per week. Wheat extracts water from top 3 foot, which means that you need approximately 0.9 inches/foot/week to meet the wheat water requirements. Most of our silt loam soils can hold 0.7 inches/foot at field capacity, which means that wheat will start showing water stress at 0.35 inches/foot (50% depletion). In other words, irrigators on a typical soil in SW Nebraska have an irrigation management span of 1 inch (in top 3 foot) to avoid water stress.

In summary, you will need 2.59 inches on demand side and available soil moisture + rain + irrigation on the supply side of equation. Frequent irrigations at 0.5 inches irrigation depth are typically recommended to allow water infiltration and avoid runoff. Probe or use soil moisture sensors to estimate what you already have in the soil get you in the ballpark.

Wheat

Wheat is at flowering stage. Hail damage observed in west Chase County. Stripe rust is moving north and is now observed in Perkins and Keith Counties. Fusarium head blight (head scab) has not been observed jet, but treating your wheat with Caramba and/or Prosaro is recommended to keep flag leaf protected from disease. Check Nebraska Extension article on “Distinguishing between head disorders of wheat” to correctly identify head scab.

Hail damage (1st and 2nd picture), stripe rust and Black chaff on whaeat in SW Nebraska
Hail damage in Chase Co (first 2 pictures), stripe rust (3rd picture) and Black chaff (4th picture) in Perkins Co

Black Chaff is a seed-borne bacterial disease that started showing up in fields where bin-run seed of susceptible varieties has been planted last fall. No treatment is recommended to control Black Chaff; planting tolerant variety and certified, pathogen-free seed are the best strategies to prevent yield losses caused by Black Chaff.

Seedling disease in corn
Seedling disease in corn

Corn

Corn growth stages range from emergence to V4. Soil borne diseases have been observed in SW Nebraska; popcorn seems to be more susceptible then field corn. Assess your field carefully for stand reduction before making decisions on replanting. Economic threshold for replanting irrigated corn planted at 32,000 seeds/ac is about 20,000 seeds/ac (about 45% in stand reduction). As fields are drying out we see more applicators spraying weeds that have been growing wild in past couple weeks. Amaranth spp. (pigweed species) started emerging.

Flowering canopies of field peas (1st pic), potatoes (2nd pic) and wheat (3rd pic). Once you see potato flower you will never forget it!
Flowering canopies of field peas (1st pic), potatoes (2nd pic) and wheat (3rd pic). Once you see potato flower you will never forget it!

Other crops

Soybean are cracking and planting is about 55% done. Planting in wet conditions can cause crusting in some areas. If crusting about

Crop report June 2

Farmers in SW Nebraska are struggling to make timely herbicide applications in muddy fields
Farmers in SW Nebraska are struggling to make timely herbicide applications in muddy fields

Wet conditions in SW Nebraska continue to interfere with timely panting and spraying operations.

Stripe rust on wheat in Chase County 6
Stripe rust on wheat in Chase County
Areal fungicide applications on stripe rust infected wheat 1
Areal fungicide applications on stripe rust infected wheat

Wheat

Wheat started flowering and it is in good condition, with the exception of stripe rust being severe in some areas of Chase County. Time to look at disease tolerance characteristics of variety being planted last fall and consider preventive and curative fungicide applications to avoid catastrophic yield losses. Rain has also increased our risk for Fusarium Head Blight. Therefore, products that work well on both stripe rust and head scab such as Caramba and Prosaro can be used while wheat is at flowering stage.

Iron deficiency in corn on high pH soils 1
Iron deficiency symptoms on corn due to high soil pH
Pea size hail damage in V3 field corn
Pea size hail damage on V3 corn. Crusting observed after corn emergence.

Corn

Corn planting is 90% done, but V3-V4 corn is also commonly found in the area. Fields show signs of farmers struggling to make timely herbicide applications. Areal herbicide application is recommended if weeds are growing out of optimal control time. In the west parts of Perkins and Chase Counties pea size hail damage is observed in corn. Research has shown that hail injury on V2 corn will not cause yield losses.

Field peas

Field peas are at V5-V9. In some fields peas look chlorotic. Symptoms are expressed most probably due to lack of sunshine and limitations of micronutrients in high pH soil. Peas should be getting plenty of nitrogen through nitrogen-fixing bacteria present in nodules. Farmers that applied inoculum should not be concerned about nodulation. Test the activity of nodules by cutting them in half. If they are red they are active! Drastic differences in conditions are observed between field pea varieties.

Varietal differences in field peas
Varietal differences in field peas
Well nodulated field peas look chlorotic due to lack of sunlight and nutrient deficiency in high pH soils
Well nodulated field peas look chlorotic due to lack of sunlight and nutrient deficiency in high pH soils

 

Other crops

Soybean planting is still in progress (about 35% done). Grain sorghum planting about 30% done.