Crop requirements for moisture, light and temperature are the major factors to consider determining the best planting date. Understanding these factors will help to decide the month or week of the year when planting should be done to obtain optimum yields. In tropical areas. Whole temperature and light are uniform, humidity will be the main factor to consider determining when to plant. In mild areas, temperature, rainfall, and day length need to be considered when determining the planting date. The best planting date for the area, based on the environmental factors and high production of the region, is reflected in the regional planting dates. Generally, planting crops out of their planting date will more likely result in lower yields, no matter how much fertilizer you use or how well you take care of the crop. Time of sowing of crop/date of planting should be based following subjects-

         i.                   Moisture: When the cropping season approaches towards the rainy (humid/wet) period, seeds may be sown when the soil is dry before rain but when the sowing season approaches towards the rainless (dry) period, seeds should be sown on semi-dry (optimum moisture for seed germination of the crop concerned) or wet soil conditions. By increasing the seed water content prior to sowing and sowing seeds more shallowly, the time from sowing to field emergence can be reduced and this can curtail the period in which the sown seeds could be affected by an adverse change in the seedbed, from the favourable conditions in which they are sown. This can be brought about by the equilibriation of the seeds with a humid atmosphere or by soaking seeds to allow the preliminary process of germination to proceed, but not enough to permit radicle emergence.

       ii.                   Photosensitivity:Certain crop varieties will not flower unless the critical day length is received for a minimum number of total days. Accordingly, planting date should be arranged so that the plant gets just sufficient time to complete its vegetative growth phase. For instance, Corchorus olitorius seeds if sown before mid-April, premature flowering would occur as the plant get the critical day length earlier before completing its vegetative growth properly.

      iii.                   Thermosensitivity:Planting date of thermosensitive crop varieties should be arranged so that the plants become able to escape the adverse temperature range. As for example, planting date of wheat should not cross mid-October to late October. Because, an increase in air temperature beyond 25°C during the flowering period reduces fertilization and yield of wheat.