Propagated only from seed. A deep, firm seedbed, free of clods, trash and surface irregularities should be prepared, either in the spring, or preferably on moderately heavy to heavy soil, in the fall and left rough over winter, thus allowing them to be worked and planted earlier in the spring. Light soil should be kept covered during the winter to prevent erosion and worked in the early spring. Soil should be worked and disked about 3–4 weeks before planting, thus allowing for partial decomposition or organic material. Corn is usually planted about 2 weeks after the average date for the last killing frost. The harvest period may be lengthened by planting successive crops, or by planting early, medium and late varieties at one time. In Florida sweet corn production is arranged for continuous harvest, with plantings from August to April. Several methods for planting the seeds are used. Planting seed singly in drills is preferred to the check-row system of planting 3–4 seeds in hills. Recommended planting rates vary from 40,000 plants per ha for medium-sized cvs to 50,000 plants per ha for small, early cvs. These rates require 11.5 to 16 kg/ha. For hills in checkrows, 3–4 plants per hill are best with hills spaced about 0.8 m x 0.8 m for small cvs and 0.9 m x 0.9 m for medium types, and 1 m x 1 m for large cvs. Seed should be planted only deep enough to place it in moist soil below the dry surface layer, this being about 2.5 cm; in sandy loams, this might be 5 cm deep. Soils should be irrigated if necessary to provide an equivalent of about an acre-inch of water every week. Yield increases in irrigated corn are greater on soils well supplied with organic matter. Green manures increase productivity of most soils. In the North, an increase in the percentage of legumes for hay or pasture and a better conservation of crop by-products and manure is frequently sufficient to maintain organic matter in moderately productive soils. A second crop of clover or a last crop of alfalfa may be turned under profitably. Sweetclover, grown with the small-grain crop and turned under the following spring is probably the most important green-manure crop in the North and is particularly useful on heavier soils. In the South where the decay and consequent loss of organic matter is more rapid than in the North, continuous during winter and summer, a larger replacement is necessary and the winter-grown green-manuring crop serves as a cover crop and checks winter erosion and loss of plant food. Also, in the South, more different crops can be grown successfully during the winter, making possible selections to fit different cropping systems. Well rotted manure may be applied to land for corn about equally well in the fall or spring unless the soil is sandy, and then it is applied in spring to prevent excessive leaching. There is little difference in the effect of well-rotted manure whether plowed under or applied as a top dressing after plowing. Commercial fertilizers are used to supply one or more of the most frequently deficient nutrients, nitrogen, phosphorous or potash. Nitrogen fertilizers promote quick and vigorous growth of stalks and leaves. Nitrogen supply of soil generally maintained more economically by turning under legumes such as cowpeas, clover, alfalfa and the like. Phosphorous fertilizers tend particularly to increase the yield of grain. Bone meal is an excellent fertilizer of this type, but it is costly. Superphosphate is the most practical form in which to supply phosphorus for immediate utilization. It may be applied after the ground is plowed and ready for planting, and can be broadcast, or applied in the row or in the hill, or both. Potash fertilizers contribute generally to the health of the plants and quality of grain. Both muriate and sulfate of potash, containing about 50% of potash, are good sources. Mixed fertilizer may also be used to advantage, but it is important to know that the fertilizer selected provides the elements needed for a particular soil. Application of commercial fertilizers in the row or hill is generally more efficient than broadcast applications. Cultivation accomplishes several purposes: controls weeds, increases absorption of water by reducing run-off, checks evaporation by maintaining a mulch and increases aeration of the soil. Weeds can be killed most easily and cheaply when the field is being prepared for planting and before the corn is up or while it is small enough to stand harrowing without injury. At such times the land can be gone over quickly with the harrow, weeder or rotary hoe. These implements are highly efficient in controlling weeds if used before the corn becomes established, and they hold down the cost of cultivation. Harrowing from just before to just after the seedlings emerge should be avoided. After corn plants are well up they may be harrowed with little danger until they are about 10 cm tall. Later cultivations can be made satisfactorily with any of the usual cultivators. Corn should be cultivated often enough to control the weeds. Cultivation should be no deeper than needed to control weeds. Shallow cultivation is less likely to injure the corn roots and does not bring many weed seeds to the surface.
Harvesting:
Sweet corn is harvested for eating from the cob when 50–75 days old depending on the cv, or when the kernels are fully developed but still juicy, producing a milky liquid when punctured, husk should be tight and the silks somewhat dried. When harvested by hand, sweet corn is picked with a downward twist, put into picking sacks or on trailers and rushed to sorting sheds. Sweet corn loses about 50% of its sugar in the first 24 hours after picking, getting it to market as soon as possible is very important. Mechanical harvesters are also used for sweet corn for the fresh market. When corn is harvested for grain, several methods may be used: ears may be snapped or husked by hand from the standing stalks, mature stalks may be cut by hand or machine and shucked and the ears husked later, grain may be gathered from the standing stalks by mechanical pickers, or machines may be used which will pick and husk the ear corn, or pick the ears and shell the corn simultaneously. Corn harvested for silage may be cut by hand, sled, mower or corn binder, and later chopped by a stationary cutter just before it is put into the silo; or it may be cut and chopped in the field in one operation by the ensilage harvester. Harvesting corn for forage applies only to that portion of the crop which is harvested for feeding, the whole plant being used either as silage or dry forage (Reed, 1976).
