With everyone from USDA Secretary Tom Vilsack to the mainstream media to celebrity chefs touting locally grown food, growing and selling sweet corn for city dwellers who pay $6 or more for a dozen ears may be a profitable niche market for strip-tillers.

In 2006, Andy McGuire, Washington State University Extension ag systems specialist compared strip-till with no-till planting in irrigated sweet corn. The research evaluated yields, root mass and soil compaction.

In 2005, the field at the Williamson Farm, near George, Wash., was in strip-tilled sweet corn and it was grazed after harvest. There is fine sand in the field, which is irrigated with a center-pivot. Residue levels taken on May 3, the day before planting, ranged from 5,011 pounds per acre between the rows to 9,479 pounds per acre in the rows.

Soil penetration resistance was measured before and after planting. Measurements were taken on March 28, 2006, in the old corn rows, 4 inches to the side of the old rows, and directly between the 30-inch rows. After planting, measurements were made in the newly planted rows of the strip-till and no- till treatments.

The field was planted on May 4 behind a custom-built strip tiller, which pulled a 12-row John Deere 1720 corn planter directly behind it. The corn was planted between the old rows. No fertilizer was applied at planting.

Four paired strips — each one pass wide and field-length long, which was about 2,500 feet — were arranged randomly in one section of the field. The strip-tiller was lifted separately for the no-till strips. However, the row cleaners on the planter moved almost all of the residue, and some soil out of the row before planting.

Soil penetration

The pre-plant measurements of soil penetration resistance indicated that the loosening effects from the 2005 strip-tillage remained under the rows. However, resistance levels increased between the rows. After planting, penetration resistance in the planted rows showed the same beneficial effects from the 2006 strip-tillage:

Yields

The average yield of the strip-till treatments was 11.1 tons per acre, while the no-till strips averaged 10.7 tons per acre. Statistically, these yields were not significantly different. The average stand count was 26,835 plants per acre. In an accompanying experiment, there was no significant difference in stand count between no-till corn planted with and without row cleaners.

While the results showed that no-tilling sweet corn after sweet corn can work, that’s not the entire story. Several weeks after emergence, patches of plants that were shorter and lighter green to yellow began to appear. Although the patches were distributed across the entire field, those in the no-till strips looked worse.

Several remedies were tried, including adjusting the water applied and applying various nutrients through fertigation. The patches of no-till and strip-till recovered and yielded well.

Although the exact cause of the problem was never determined, one prime candidate was over-irrigation — perhaps due to increased water in the soil resulting from the residue that covered the soil and reduced evaporation.

This would explain why the patches in no-till looked worse. Because there was too much water and too little oxygen, the plants suffered more in the denser soil.

But it’s puzzling that the much-denser soil in the no-till plots did not result in decreased yields. Some scientists suggest that soils with penetration resistances above 300 psi limit root growth.

This does not account for root growth down existing pores, but this is not likely in a sandy soil with little structure. Planting between the old rows probably created the worst conditions for root growth.

Rooting patterns after harvest were assessed by digging up root balls. It appeared that the no-till corn roots did not go as deep as plants in the strip-till plots. But the root balls in the no-tilled treatments may have been denser in the upper 6 inches. It’s possible that the roots did not need to go very deep because they were “spoon-fed” a sufficient supply of water and nutrients through irrigation.

Compaction from harvesting the sweet corn in the field of fine sand may have been a problem, too. Sandy soils with low organic-matter levels and small proportions of silt and clay particles do not easily form a soil structure that resists compaction. That’s especially so if the soil were wetter than the producer would like it to be when the corn is harvested. This also would argue for a strip-till over a no-till in this situation.