January 9, 2009

In Rain Fed Corn

Robert N. Klein, Western Nebraska Crops Specialist

The idea behind skip-row planting is to keep developing corn plants from using all of the available soil water too early in the growing season. Because water in the soil between widely spaced rows cannot be reached by the crop until later in the season, water is available to plants in July and August. Corn is very sensitive to drought in the silking to blister stage of development, which occurs in July and August.

Skip-row corn research began in Nebraska in 2003. In this first trial, all rows of corn were planted and then plants were removed to reduce population, or one or two rows were removed on July 2. A breakdown of yields from this trial follows:

1. control (19,5000 population): 41 bu/ac;
2. removing approximately every third plant (14,700 population): 41 bu/ac;
3. removing every other plant (11,200 population): 45 bu/ac;
4. series of two rows of corn followed by one row removed (equivalent to 13,800 population): 48 bu/ac (17 percent above the control); and
5. series of two rows of corn with the next two rows removed (equivalent to 9,500 population): 54 bu/ac (32 percent above the control).

By July 2, corn will have used 6 inches of soil water. Yields may have been further increased with the skip treatments.

Figure 1. Yields of skip-row rainfed corn at North Platte in 2004.

In 2004 and 2005 research trials were conducted at several sites across Nebraska (Concord, Lincoln, Clay Center, North Plate, Hayes Center, Ogallala, Sidney, and Scottsbluff, (Figure 1a) and Tribune, Kan., and Akron, Colo. (Figure 1b). The treatments consisted of three corn populations and four skip-row configurations. The skip-row configurations were:

1. no skip-row (control),
2. a skip-row every two planted rows,
3. a skip-row alternating with a planted row (single-skip), and
4. two skip-rows alternating with two planted rows (double skip).

There was no irrigation except at Scottsbluff where a reduced irrigation trial was compared to a non-irrigated trial. 

The results of the 2004 skip-row plots at North Platte are shown in Figure 1. These are with very favorable precipitation during the growing season. June precipitation was 35% above average, July was 88% above average, and August was average. Even with this very favorable precipitation, the plant-two skip-one out-yielded the solid planting at all population levels.

Table 1 lists the yield possibilities for skip-row corn in a plant-two, skip-one configuration and Table 2 lists plant-two, skip-two yield possibilities. In an Iowa study where six rows of corn were planted next to six rows of soybeans, the outside rows of corn yielded 20% more on the average. If we use 0.5 lb ears as the standard, we would expect the rows in a skip-row to be at least 0.6 lb ears and maybe 0.62 lb ears since there is no row next to them.

Table 1. Yield possibilities for skip-row corn in a plant-two, skip-one configuration.
Planted pop. in 2 rows/ac	Stand pop in 2 rows planted/ac	Stand pop. in 3 rows (2 rows planted)/ac	Ear wt/lb yield/bu	Ear wt/lb yield/bu	Ear wt/lb yield/bu	Ear wt/lb yield/bu
20,000	18,000	12,000	0.5 = 86	0.6 = 103	0.62 = 106	0.7 = 120
24,450	22,000	14,667	0.5 = 105	0.6 = 126	0.62 = 130	0.7 = 147
28,900	26,000	17,334	0.5 = 124	0.6 = 149	0.62 = 154	0.7 = 173
33,333	30,000	20,000	0.5 = 143	0.6 = 171	0.52 = 177	0.7 = 200
Table 2. Yield possibilities for skip-row in a plant-two, skip-two configuration.
Planted pop. in 2 rows/ac	Stand pop in 2 rows planted/ac	Stand pop. in 4 rows pop. (only 2 planted)/ac	Ear wt/lb yield/bu	Ear wt/lb yield/bu	Ear wt/lb yield/bu	Ear wt/lb yield/bu
20,000	18,000	9,000	0.5 – 64	0.6 = 77	0.62 = 80	0.7 = 90
24,450	22,000	11,000	0.5 = 79	0.6 = 94	0.62 = 100	0.7 = 110
28,900	26,000	13,000	0.5 = 93	0.6 = 111	0.62 = 120	0.7 = 130
33,333	30,000	15,000	0.5 = 107	0.6 = 129	0.62 = 140	0.7 = 150

 

Advantages of Skip-row, No-till Planting

No-till offers several advantages with appropriate levels of crop residue: 

• Much greater moisture savings: After base needs are met (10 inches of soil water) corn yields can increase 12.5 bushels per acre with every one-inch increase in soil water available to the crop.
• Much faster soil infiltration of water (Maintaining a good crop residue cover is key to its success.)
• Higher yields

The greatest benefits can be derived from ecofallow corn.

Yield of the following corn crop increases with increasing wheat crop residue levels: 6,000 pounds residue per acre, approximately 60 bushels of grain per acre.

Implement Skip-row Planting

To maximize rainfed corn yields in Nebraska with no-till skip-row planting, remember: 

• Cut the wheat high to maximize stubble height, leaving 15-18 inches of standing stubble. Missing one average head, which has 22 kernels in every square foot, reduced harvested yield by about one bushel per acre, but the yield of the following crop can be increased significantly through the benefits of the taller stubble. Many lower heads have only 7 to 15 kernels, and in many cases, it would take two or more heads per square foot to equal one bushel. A Kansas State University study found a 2-bushel increase in corn yield for every inch of height increase in wheat stubble from 1.5 to 15 inches.Taller stubble traps more snow and takes much longer to disintegrate in the field than straw that has gone through the combine.
• Spread the straw and chaff uniformly.
• Spray wheat stubble shortly after harvest to control weeds.
• Do not harvest ecofallow corn for silage if you intend to plant corn in the same field next year. Residue is critical to moisture savings. Also, don't cut the corn for silage if you plan to seed no-till winter wheat.

Crop insurance is now available in some Nebraska counties for skip-row planted corn. If you're planning to plant skip-row corn, be sure to check on your crop insurance options.

Fertilize Appropriately 

• Fertilize according to your yield goal.
• Apply nitrogen over the entire area. Use UAN solution with pre-pant herbicides or apply urea before planting, the earlier the better. Later applications (urea, UAN or anhydrous ammonia) may not receive sufficient rainfall to move nitrogen into the root zone.
• Anhydrous ammonia application is also discourage because the knives can increase evaporation loss from the soil and plant weed seeds.

Practice Skip-row Planting Correctly 

• Follow the recommendations listed above for growing ecofallow corn.
• Select Bt, Roundup-Ready hybrids that perform well under ideal or stressful situations.
• Typically, on a 30-inch row system, two rows are planted and two rows are skipped. For higher rainfall areas and/or fields with large amounts of crop residue and a full soil profile, the plant-two, skip-one configuration may be the better choice. Also, the plant-two skip-one may be a better choice in short season areas and where corn does not get tall.
• Plant appropriate plant populations: 10,000 to 13,000 plants per acre in western Nebraska. On a plant-two, skip-two system, this translates to 20,000 to 26,000 plants per acre in the planted rows, but since every row is an outside row reduce these in-row populations by 20 percent. If you normally plant a population of 12,000 in conventional no-till fields, that would compare with 24,000 in a plant two, skip-row system. Reduce that by 20 percent (4,800), to 19,000 plants in the two rows that are planted. In eastern Nebraska and in limited irrigation and/or where water may not be available later in the season, consider the plant-two skip-one system and plant about 19,400 seeds per acre. (This is about 29,000 in the two planted rows if you are trying for 150 bu/ac corn.)
• It usually works best to fill the outside seed box on each end of the planter, and skip the approximate boxes from there.
• Apply a pre-plant or pre-emergence herbicide treatment. If weed populations are light, consider a two thirds rate; however, remember that the chemical company will not stand behind reduced rates.
• Spray glyphosate postemergence, as needed, to control weeds. Always consult and follow the pesticide label.

Potential Disadvantages of Skip-row Planting 

• Yields will be limited to approximately 120 (plant-tow, skip-two) and 160 (plant-two skip one) bushels per acre (not a likely deterrent in western Nebraska).
• Crop insurance may not be available or only partially available.
• The Farm Service Agency may not count all acres as planted acres.
• Fields may be more attractive to corn borer because they are greener and healthier. (Plant Bt corn hybrids.)