Seedbed requirements

Listed below are the seedbed requirements for some important crops. 

Seedbed requirements and methods of sowing are sirrrilar to those for wheat crops. 

Treatments to prepare the site for seeding or planting are determined after evaluation of site data and establishment of the land-management options and objectives. Grass and legumes often require more surface preparation than trees and shrubs. Uncompacted fill slopes and freshly reshaped surfaces may make acceptable seedbeds. Hard crusts form on many spoils fine clay-size particles are consolidated by the drying action of wind and sun. This crust may be broken by rainfall, frost, or mechanical scarification. In many cases, ground cover will be denser if it is seeded into fresh spoil or where spoil surf.ices have been broken by natural or mechanical scarification. 

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. 

Tillage operations in connection with the stubble-mulch system are ordinarily kept to the minimum necessary to prepare a suitable seedbed, and to keep weeds under control. Usually the sweep or blade is used for lifting the soil initially and killing the weeds. It operates at depths of up to six inches with subsequent tillages with various implements at lesser depths. Draft requirements for the sweep cultivator are usually about 70—80% as great as for the moldboard plow operating at the same depth. 

Tilth is a term used to describe the condition of the soil in a seedbed. For example, the soil may be in a finely-divided state or it may be rongh and litmpy. Whether a tilth is suitable or not partly depends on the crop to be grown. In general, a small seeded crop requires a finer tilth than large seeds. 

Root crops, e.g. sugar beet, swedes and carrots also kale. These crops have small seeds and so the seedbed must be as fine as possible, level, moist and firm. This is very important when precision drills and very low seed rates are used. Good, early, ploughing with uniform, well-packed and broken furrow shces will considerably reduce the amount of work required in the spring when, if possible, deep cultivations should be avoided to keep frost tilth on top, leaving unweathered soil well below the surface. 

A fairly rough autumn seedbed is adequate for winter wheat and helps prevent soil-capping in a mild, wet winter. When soil-acting herbicides are used a fine seedbed is required. In a difficult autumn, winter wheat may be successfully planted in a wet sticky seedbed and usually it still produces a satisfactory crop. Spring wheat should only be planted in a good seedbed. 

Generally a finer seedbed than wheat is required. Shallow sowing at 3-5 cm is important. 

Requirements are similar to those for eereals but ideally a little deeper. As a result of soil type and estabhshment method, the autunm seedbeds are fairly rough and may impair the aetivity of soil-aeting herbicides. 

At index 2, 40 kg/ha of P and 30 kg/ha of K are required in the seedbed assmning a 3.5t/ha yield. 11kg of extra P and 12kg of extra K will be needed for every torme of yield above 3.5. However, allowance should be made for nutrients applied as organic manures. No nitrogen fertiliser will be required, but a magnesium fertiliser will be required at soil index 0 and 1. 

Slugs may be a serious problem for winter beans especially where the crop is late sown in a cloddy seedbed and metaldehyde or equivalent should be used. Rooks and pigeons may also damage the crop and bird scarers or other methods of control may be required. 

Ploughing in the autumn and allowing weathering to occur will allow the preparation of a seedbed with a minimum number of cultivations because peas are sensitive to over-compaction and do not require too fine a tilth. On very light land, spring ploughing will work which allows over-wintered stubbles. 

Other plant foods required can be summarised as in Table 15.4, assuming phosphate and potash indices at 2 to 3. Kainit can be used at 500-600 kg/ha instead of potash, salt and magnesium (except in severe cases of magnesium deficiency where Kieserite is still necessary). It should be applied some weeks before sowing the seed. The phosphate and potash can be broadcast and worked into the seedbed at any time over the preceding winter months. 

Pre-sowing treatments, using contact-acting products like glyphosate, may be required to kill weeds that have not been controlled during seedbed cultivations. 

Fine seedbeds are required for uniform emergence of baby leaf crops. This can be achieved using power harrows following discing. Baby leaves are commonly grown in beds to minimise compaction and aid harvesting. 

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