Best Management Practices in Ecofallow No-Till Sorghum
By Charles Ikard
By Charles Ikard
Nebraska research specialists define ecofallow as controlling weeds during the fallow period by using herbicides and/or tillage with minimum disturbance of crop residues and soil. This concept has been used for over 20 years. Ecofarming is defined as, a system of controlling weeds and managing crop residues throughout a crop rotation with minimum use of tillage. This technique is used to reduce soil erosion and production costs while increasing weed control, water infiltration, moisture conservation and crop yields. No-till sorghum fits well within an ecofarming system.
Ecofallow helps maximize soil water storage. Maintaining crop residue cover is important to increasing stored soil moisture in the following three ways:
Scientists from Kansas State University report rain falling on bare soil can seal off the soil within the first 30 minutes, depending on soil texture and rainfall intensity. As little as one half inch of rainfall can seal the surface of bare soil.
When the soil surface becomes sealed, infiltration slows or ceases and water begins to run off. Surface residue slows runoff and can increase the available time for infiltration by two to threefold. Soil residue, especially standing stubble, provides an added benefit in trapping snow. In western Kansas, moisture from snow can add 1.6", in an area where soil water available to plants from rainfall is only about 2.5" (10" rainfall during growing season and 25% efficiency). The University of Nebraska reports trapped snow can result in one to three inches of additional water being available for crop production, making snowfall an extremely valuable source of soil moisture. Tillage regularly results in significant soil moisture losses. Data from Colorado shows soil water losses from different tillage operations in Table 1.
Evaluating yield results from multiple locations, two conclusions can be made.
If over 3 feet of soil moisture is available, sorghum can be successfully planted following a previous sorghum crop. A good management approach is to probe for soil moisture before planting.
Plant wheat seed that has been professionally cleaned to provide good germination and stand establishment, to help reduce weed competition. Planting in narrow rows will provide ground cover more quickly, but drills with wider spacing may produce better stands under dry soil conditions. Check wheat fields in early March and spray broadleaf weeds if necessary. Use a straw spreader on harvesting equipment to distribute straw evenly rather than in rows. Spray weeds with a burn-down herbicide after wheat harvest.
Residue covering 20% of the soil surface can reduce erosion by 50% compared to soil with no covering. Residue on 40 percent of the soil surface can reduce erosion by 75% compared to bare soil.
Proper fertilization is essential for good grain and straw yields. Use soil tests to determine fertility plans for desired yields. Phosphorus is very important in winter wheat, as adequate fertility makes the crop more competitive with winter and spring weeds. Dual injection of anhydrous ammonia and phosphorus in 12-inch spaced bands is an effective pre-plant fertility method. Avoid top dressing when soil is wet or soil compaction will result. Ecofallow used with No-Till increases soil moisture.
The following data tables show advantages of tillage methods for increasing soil moisture to following crops.
|Years||Tillage System||Number of Tillage Passes||Annual Rainfall||Fallow Water|
|1931-45||Disk Conv. Till||5-7||15.8"||4.4" Storage|
|1946-60||Improved Conv. Till||5-7||16.4"||5.4" Storage|
|1961-75||Stubble Mulch Min Till||2-4||15.3"||6.2" Storage|
|1976-90||Min Till to No-Till||0-2||16.2"||7.2" Storage|
|Tribune, KS||144 lbs.||280 lbs.|
|Garden City, KS||163 lbs.||290 lbs.|
|Walsh, CO||118 lbs.||215 lbs.|
|Bushland, TX||87 lbs.||216 lbs.|
Starting an ecofallow system requires determining a desired crop rotation. Options include wheat-fallow (WF), wheat-sorghum-fallow (WSF), or continuous sorghum (SS) rotations.
Kansas State University research shows wheat fallow did not return enough to cover expenses without government payments. Their data also shows WSF rotations will return a profit without government payments and with less relative risk than WF rotations. Continuous sorghum and WSF systems were most profitable in Texas.
The following graphs show grain yield results from different locations in the Great Plains under various crop rotations.
Starter fertilizer is important in no-till cropping due to potential cool soil conditions at planting and the difficulty of incorporating this into the soil. There are a number of benefits from starter fertilizer, such as increased early growth and more uniform plant development. University of Nebraska data shows yield increases from starter fertilizer are more dramatic in soils testing low in phosphorus (15 ppm or less). Kansas State University researchers evaluated starter fertilizer (30-13-0) and determined adequate applications hastened sorghum maturity by six days.
Weed control is critical in ecofallow cropping systems to help prevent the loss of soil moisture to non-crop plants.
|Pigweed||287 lbs. water used / lb. dry matter produced|
|Sorghum||304 lbs. water used / lb. dry matter produced|
|Corn||349 lbs. water used / lb. dry matter produced|
|Wheat||528 lbs. water used / lb. dry matter produced|
|Lambsquarters||801 lbs. water used / lb. dry matter produced|
|Ragweed||948 lbs. water used / lb. dry matter produced|
Weed control basics – wheat-sorghum-fallow rotation after wheat harvest:
Early seedling vigor is important for successful no-till sorghum. Most Pioneer grain sorghum hybrids have excellent early growth and are suitable for no-till planting. Color score is important for later plantings. Higher color scores represent better hybrid maturity in cool weather.
Planting dates are defined by geography and weather patterns. Later maturing sorghums generally have higher yield potential than shorter-season hybrids. Adequate soil temperature and moisture are essential for developing a good early stand. A general rule of thumb is to plant sorghum about 2 weeks following the ideal time of corn planting in a given area. Soil moisture can be checked by probing the soil with a 6-foot metal penetrometer, just prior to planting. Yields can be maximized by planting a hybrid that will head during the wettest part of the growing season.
Sorghum has the ability to compensate well for low seeding rates and will tiller to fill in open spaces. However, low seeding rates can improve the ability of sorghum to better tolerate drought conditions. With precision row-crop planters, lower seeding rates are easily achieved, while planting with a drill usually results in over-planting and is not recommended.
Yields of over 8,000 pounds per acre (143 bushels) are possible with seeding rates as low as 30,000 seeds per acre (recommended low seeding rates vary in different regions). Make sure good quality, high germination seeds are used when planting reduced rates of sorghum.
Always plant based on seeds per acre and not pounds per acre. Sorghum hybrids can vary from 12,000 to 16,000 seeds per pound and if planted by weight could produce populations too high for optimal crop growth. Sorghum may also lose staygreen and not head under drought stress when plant stands are too dense. Thick stands result in smaller diameter stalks, which under most growing conditions will contribute to increased plant lodging.
Sorghum requires higher soil temperatures for germination and emergence than corn. Best germination is obtained when the soil temperature is 65 F and above. Sorghum is frequently planted at lower soil temperatures and will do relatively well if seedling vigor is strong. Data from Colorado indicates soils with 3,000 pounds per acre of residue are typically from 8 to 10 degrees cooler than bare soil. Table 5 shows reduced stands in no-till sorghum had no effect on grain yield.
Table 5. Effect of different tillage methods of sorghum stand establishment
|Tillage||Final Stand||Grain Yield in Bu.||Grain Yield in Lbs.|
|Conventional Tillage||89,633 Seedlings/A.||94.47 Bu./A.||5,290 Lbs./A.|
|No-till||78,067 Seedlings/A.||94.35 Bu./A.||5,284 Lbs./A.|
Conventional tillage involved 10 trips including harvest. No-till had 5 trips including harvest. Three year study from Temple, Texas (rainfall from 12" to 20").
Cruiser 200 insecticide applied as a seed treatment provides good control of soil insects and early-season pests. Scout fields throughout the growing season for insect populations that may reach economic thresholds later in the growing season.
Stalk rots can be a common occurrence in dryland sorghum production because of the stressful growing conditions. Management practices of planting hybrids with good tolerance to stalk rot and using moderate seeding rates for expected in-season soil moisture conditions help prevent stalk rots. No-till sorghum is usually under less moisture stress than conventional sorghum due to enhanced moisture stored in the soil. In a 3-year test in Nebraska, stalk rot was reduced by 28% under no-till management and grain yields were higher than conventional-tilled sorghum.
Charles Ikard began with Pioneer Hi-Bred in 1975 as an agronomist and is currently enjoying retirement. He holds a Bachelor of Science degree in agricultural engineering from Oklahoma State University and. has more than 40 years of experience growing and evaluating sorghum.