Chapter 17

Soil Management for Field Crops

Conservation Tillage Systems

Conservation tillage is a program of crop residue management aimed at reducing erosion. Conservation tillage may also be known as reduced tillage or minimum tillage, though these terms may also be applied to systems that reduce tillage and leave lesser amounts of surface residues than conservation tillage. Rather than plowing under crop residues, some or all residue is left on the soil surface. The working definition of conservation tillage requires that 30 percent or more of the soil surface be covered with crop residues after seeding. Crop residues, a renewable resource, play a key role in conservation tillage. When crop residues are properly managed, they protect soil resources; enhance soil quality; restore degraded ecosystems; improve nutrient cycling; increase water conservation and availability; reduce runoff and leaching of nutrients off-site; and sustain and enhance crop productivity and profitability. Of course, the residue cover partially depends on the amount and quality of residue left after harvest, which may vary greatly among crops and harvest method (corn harvested for grain or silage is one example).

No-Till

No-till is a procedure whereby a crop is planted directly into the soil with no primary or secondary tillage since harvest of the previous crop (Figure 17.13). In practice, a tillage system that leaves more than 70 percent of the surface covered by crop residue is considered to be a no-till system. The no-till system loosens the soil only in a very narrow and shallow area immediately around the seed zone. In its simplest form, no-till planting is a one-pass operation accomplished with a multi-component implement (e.g., row cleaner, coulter, seed furrow opener, or other device attached to the planter or drill) that slice through surface residue and the top three or four inches of soil, drops seeds into the slot, and squeezes the slot back together over and around the seed, leaving little or no visible evidence that the crop has been planted.

Strip-Till

Strip-till is a conservation tillage system that was developed for row crops grown in heavy, poorly drained cool soils (Figure 17.14). Strip-till removes the residue from the row area, allowing sunlight to hit the soil surface to warm the soil and to increase soil evaporation. Row middles are untilled and covered with undisturbed crop residue. Planting with strip-till takes place in the residue free strips.

Ridge-Till

Ridge-till is a conservation-tillage system where crops are grown on permanent beds or “ridges” (Figure 17.15). With ridge-till, the soil is left undisturbed from harvest to planting except for possible fertilizer application. Typically, ridges are built and reformed annually during row cultivation.

Mulch-Till

Mulch till includes any conservation tillage system other than no-till and ridge till. According to NRCS, mulch-tillage, also known as residue management, manages the amount, orientation, and distribution of crop and other plant residue on the soil surface year-round while limiting the soil-disturbing activities used to grow and harvest crops in systems where the field surface is tilled prior to planting. Mulch till systems can work under field conditions that do not work well for no-till. Mulch till is better suited to heavier soils, high crop residues, cover crops, plowdowns, and additions of organic amendments such as manure and compost.

Disadvantages of Conservation Tillage

Despite the apparent conservation tillage benefits, these tillage practices also have disadvantages. The initial investment in no-till equipment and parts can be one of the major deterrents to switching from conventional tilling to no-till planting. Even if this cost is eventually absorbed into day-to-day operational savings, it’s a significant upfront expense. Continuous no-till, particularly when fertilizers are surface applied, will result in nutrient stratification.

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