Sowing seed without turning the soil

The single, hand-guided moldboard plow has long been an agricultural museum piece in America. Now it may be joined by the more modern land-tilling methods. Within the last decade, many American farmers have turned from traditional plowing-when-planting to conservation-tillage practices. That means little or no plowing of the soil before planting.

Basic reasons for the change, according to the USDA's Economic Research Service, are to save fuel and reduce manpower needs and equipment - without any detriment to crop production.

Other things favoring conservation tillage are the preservation of soil moisture in water-scarce areas; the accelerating trend toward prevention of further soil erosion and water runoff; and the time gained in some cases of double-cropping. An example would be the planting of soybeans directly in wheat stubble behind a combine - rather than waiting several days to prepare the soil for conventional seeding.

What's the difference between the old and the newer methods?

Whereas the normal, long-used type of tillage mixes topsoil through plowing, power tilling, or multiple disking, conservation style depends on minimum soil disturbance. Methods vary, but in general the plant residues are simply left on the surface of the ground. Perhaps only the seed zones are prepared - with fertilizer scattered on the surface - or perhaps the entire field is given some form of limited soil preparation.

There are considerable regional variations in the use of the newer methods. Almost half of the crops in the Southeast United States are grown by this method (47 percent), along with about one-third of the Corn Belt plantings (34 percent). But all regions use the conservation methods to some extent.

Critics of the no-tillage procedures claim the method requires more pesticide usage because of added weed and insect problems. They also point out that percent-of-yield research weighing the two methods has so far been inconclusive. But USDA economists say there continues to be growing interest in the farming community about no-tillage methods - if only for the significant long-term savings.

Increases in minimum-and no-tillage acres

9-year percentage Acres 1973 1982 Increase Minimum tillage 39 million 100 million 157% No tillage 5 million 12 million 140% Conventional tillage 203 milion 204 million -- Source: No Till Farmer, from US Soil Conservation data