Mechanical cultivators

To control weeds, approximately 90% of U.S. agricultural acreage is treated with nonchemical, mechanical weed controls, such as mechanical cultivation and rotary hoes (15), whereas only about 25% receives treatment with herbicides (13). 

Compaction occurs when soils are regularly walked on or cultivated in wet conditions. It is a particular problem in heavy soil. Avoid it by creating paths that follow the routes you want to take around the garden, and planting beds that are narrow enough to be worked on from paths. Regular use of a mechanical cultivator can also create compacted hard pan below the soil surface that plant roots cannot penetrate. 

Flame cultivation was attempted in sugarcane in the 1940s (Conrad and Lucas, 1995), but was soon abandoned. Liquid propane flamers burned broadleaf and grassy weeds as shields partially protected the crop from thermal damage. While flame cultivation was only marginally useful in sugarcane, tractor-mounted weed burners have been important in the transition from dependence on repetitive mechanical cultivation to the concept of chemical energy for weed control. 

Farmers use cultivation and herbicides in their weed control programs because of their complementary nature in controlling weed species that are missed if exclusive reliance were to be placed on either technique alone. One way to decrease herbicide use with additional cultivation while controlling weeds in the corn row is to band the herbicide over the row of corn plants. Essentially, the herbicide controls the weeds within the row, while the weeds between the rows are effectively controlled with mechanical cultivation. 

A publication from the Land Stewardship Project describes four sustainable farms in Minnesota (Chan-Muehlbauer et al, 1994). None of the four farmers use herbicides in their corn fields. For weed control they rely on extended crop rotations with alfalfa, mechanical cultivation with a rotary hoe and cultivator, and late planting of com to allow mechanical control of the first flush of weeds. One farmer reported that the com crop is cultivated three to five times. The report details the 1992 com yields at these four farms in comparison to the average yields in the same regions. In all cases, the yields of the sustainable farms were lower than the average yields in their regions. The reduced yields for the four farms were -38%, -11%, -7%, and -5%. 

After World War II, modern chemical weed control was introduced. Chemical herbicides not only reduced the human energy required, but also reduced the amount of mechanical cultivation. We estimate human energy input for overall weed control in the United States today at no more than 5%, with only a trace of animal energy input mechanical, at 40% and declining with herbicides responsible for the remainder. Thus, the... 

Herbicides have provided a more effective and economical means of weed control than mechanical cultivation. Together with fertilizers and improved varieties of plants, herbicides have made a immense contribution to increased yields and reduced costs. 

Before the advent of herbicides, weeds were removed by mechanical cultivation. Herbicides were adopted because they made weeding cheaper without any mechanical damage to the crop. Both methods involve more erosion of soil than is desirable. There are some other ways to cut down on the crop losses to weeds.205... 

The fineness of the limestone affects the rate at which it can react in the soil. Particles of hard limestones do not break down in the soil as a result of the action of frost, or of mechanical cultivation, and it is generally considered that particles larger than 600 pm react too slowly to be effective. 

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