Irrigation of grassland

Abstract

In many parts of the world crops can only be grown if the land is irrigated. Whilst this is not true of Britain, there are areas, south-east England in particular, where plant growth is limited by lack of water. The effect is particularly noticed on pastures.From the time of its establishment in 1928, Jealott's Hill (mean rainfall 25-7 in.) has been concerned with obtaining the maximum production from grassland. This involved not only trying to increase the over-all yield, but attempting to maintain as constant a rate of growth as possible during the summer months and thus overcoming the midsummer decline which normally follows the spring flush. It was soon apparent that the maximum response to fertilizers could not be obtained if the water supply was inadequate.Greenhill (1935) set out to find what is an adequate rainfall to maintain uniform growth under Jealott's Hill conditions. His approach was largely empirical. In a replicated plot trial, he supplemented, by watering one day each week, the natural rainfall, provided it had not reached one of the predetermined levels in the previous week (0-69and0-84 in.).In a year in which the spring and summer rainfall was above average he increased the yield by about 20 % for the lower ' rainfall' and 36 % for the higher.

The Effect of White Clover and Nitrogenous Fertilizer on the Production of a Sward

“…Under dry conditions, irrigation improves the uptake and utilization of N. Usually it fails to improve response to N of mixed swards because it also enhances the contribution from clover in the control plots (4,9,14). It is perhaps not surprising that, where shortage of nitrogen limits production, white clover, which can fix nitrogen, will make a greatly increased contribution when an inadequate moisture supply is corrected.…”

The Effects of Level of Nitrogen Fertilizer on Beef Production From Grazed Perennial Ryegrass/White–clover Pastures

“…Natural rainfall in Britain varies greatly from month to month, from year to year, and from the drier eastern counties of England across to the higher rainfall areas in the west. Herbage yields may be affected by soil-moisture deficits and it has been found that white clover does not grow as well as perennial ryegrass when a moisture deficiency exists (8). A relatively light application of N fertilizer has been found to reduce the clover content of pastures at Hurley, total production not being increased until 235 kg N/ha were applied annually (6).…”

The Response of S24 Perennial Ryegrass Swards to Irrigation

“…Overwatering may depress yields (12,15), but this is unlikely on a free-draining soil (16). Apart from any possible loss in yield or waste arising from overwatering, practical considerations, to keep labour and equipment costs to a minimum, would require that swards should be irrigated as infrequently as possible, consistent with a worthwhile improvement in yield.…”

“…This suggests that economy in both the amounts of water used and in the frequency of irrigation may be achieved by applying water only in sufficient quantities to enable the roots in the upper horizon of soil to absorb the nutrients while making further use of water from a greater depth. The work reported here investigated the efficiency of use of irrigation water, particularly when used in quantities less than that indicated by the soil water deficit INTRODUCTION Previous reports on the irrigation of grass or grass/clover swards have shown that the more frequently a sward is irrigated and the nearer to field capacity the soil is maintained the greater is the yield response to irrigation (12,13,16).…”