Tillage and cultivations

Listed below are the seedbed requirements for some important crops. 

Spring beans and peas. The requirements will generally be similar to the cereal crop, although the tilth need not be so fine. Peas grown on light soils may be drilled into the ploughed surface if the ploughing has been well done. 

Winter beans These are often broadcast onto stubble and ploughed in. The surface is then levelled to make travel across the field more comfortable and to kill ary weeds which have emerged. 

The main implements used for tillage are described below. 

Rotary power harrows can result in much better movement of the soil in one pass. They are most valuable on the heavier soils when preparing fine seedbeds for potatoes, sugar beet and other crops. Power harrow/drill combinations are used by some farmers as one-pass operations to prepare seedbeds for cereals. They can be used in conditions where ordinary drills may not be appropriate. 

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Herbicides reduce mechanical tillage costs (2 ). Each year in the United States, 250 billion tons of soil are moved, much of it several times, in tillage and cultivation operations. This amount of soil would make a ridge 100 feet high and one mile wide from New York to San Francisco. The movement of this soil each year is the world s largest materialhandling operation. At least one-half of this soil-moving function is practiced solely for the control of weeds. 

Many of our current technical innovations in mechanical weed control can trace their development from earlier forms of the same tillage device. Even the plows and cultivators used through the 1900s tended to be little more than large, hardened steel replacements of the wooden tools used centuries earlier. On the other hand, herbicides radically changed agricultural production within a few years of their introduction. Novel application equipment is now required by the herbicide user, as is the knowledge to use each new herbicide product effectively. 

Cultivation of soils that are somewhat below optimum moisture will produce less damage to aggregates but the production of a good seedbed under such conditions requires more intensive tillage. The cultivation of a very dry soil will result in the shattering of some of the clods and the production of many dust particles. The overall effect on aggregate formation in such a soil, apart from the breakup of clods, is negligible. If the main purpose of the cultivation is to break up clods it is advisable to wait until moisture conditions are more favorable. 

An annual estimated cost of approximately 938,835,000 is required for labor and equipment to apply 204.5 million kilograms of herbicides to 147.6 million hectares of cropland in the United States (Table IV). Mechanical tillage to control weeds between cropping seasons and interrow tillage of crops has been used for centuries as a very effective method of weed control. Approximately 50% of all tillage between crops is done to control weeds. The number of cultivations required for effective weed control within a row crop varies from two to five during a cropping season. 

Yang CH, Crowley DE, Menge JA (2001) 16S rDNA fingerprinting of rhizosphere bacterial communities associated with healthy and phytophthora infected avocado roots. FEMS Microbiol Ecol 35 129-136 Yemefack M, Jetten VG, Rossiter DG (2006) Developing a minimum data set for characterizing soil dynamics in shifting cultivation systems. Soil Tillage Res 86 84-98... 

Various forms of soil cultivation, or non-cultivation, exist ranging from mouldboard ploughing to no-tillage, as listed below (from CTIC and Conservation Technology Information 1998) ... 

Mulch tillage or mulch ripping the soil is tilled prior to planting with chisels, disks, sweeps or blades weed control is obtained with herbicides and/or cultivation... 

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