CROP PRODUCTION

Timaru Herald, Volume CXLVIII, Issue 21821, 26 November 1940, Page 3

CROP PRODUCTION

Water And Plants The Limiting Factor Many plants may have less than 10 per cent of dry matter. Badly grown white turnips, for example, may have as much as 92 per cent of water in the bulb. That is, out of every hundred tons of roots carted off a field there are only eight tons of dry matter. In many seasons water is the limiting factor in crop production—that is to say, lack of water checks development. When water is scarce, plants are unable to obtain sufficient water for transpiration and cell development. They, therefore, cause their leaf and stem growth to slow down, and concentrate upon keeping themselves alive during the drought. Often this is a matter of extreme difficulty, try how they may, they cannot entirely stop the loss of water through transpiration (i.e. evaporation through the leaves) and they consequently wilt and perish. Herbaceous Plants It may be mentioned that herbaceous plants are kept rigid by water. The water in their cells is normally under considerable pressure, which makes the walls rigid in the same way that the air in a bicycle tube makes the whole tyre hard and resilient. Wilting is due to the removal of water from the cells, which lowers the pressure and leads to partial or complete collapse of the tissues. When water is superabundant during a growing season, plant growth may be both accelerated and hindered. Forage plants, such as the grasses and clovers, can stand a very great deal of water so long as the soil does not actually become water-logged and it is a common observation that a wet spring and early summer leads to a great bulk of hay.