Home & People Autumn is lime time

Press, 12 April 1979, Page 14

Home & People Autumn is lime time

Autumn is traditionally considered the best time to apply lime to the garden. This has perhaps come about because it is at this period of the year that the vegetable garden carries the least crop; it is then that the ground is usually dug over to lie fallow during the winter. It is also preferable to lime a soil in advance Of planting and sowing. Regular applications of lime are beneficial to cropping soils, particularly if acidic fertilisers are much used. Lime must, however, be applied with some discretion because it can be overdone and thereby create serious problems. Too heavy or continuous applications of lime can induce excessive alkalinity of the soil. Most plants prefer a slightly acid medium for

optimum growth while some, such as those which belong to the Ericaceae family — for example, rhododendrons and ericas — tolerate only slightly acid soils. Such plants will generally register their displeasure by failing to thrive, turning yellow of leaf and even dying if the situation is not remedied in good time. The acidity (or alkalinity) of a soil affects the feeding of the plant. Iron is one of the most essential minor elements required by plants; it is vital to them for the production of chlorophyll, the green pigment of leaves and other appendages. A lack of iron induces a yellowing condition in the leaves, particularly on young foliage, which can result in stunting of the whole plant and even dieback of the growing tip in severe cases. Iron defi-

ciency is a fairly common complaint in alkaline soils. Excessive application of lime can also create reverse problems such as rendering nitrates too available so that they are lost by leaching; in the

case of manganese it can actually go either way.

The other beneficial effects of lime concern the soil structure and organic matter content. The addition of lime to heavy clay soils promotes a process called flocculation, whereby soil particles tend to aggregate thus making cultivation

easier. Organic matter in a soil is more rapidly broken down in the presence of adequate lime as it induces greater activity of certain bacteria and fungi and also earthworms, all of which become more subdued in acidic conditions. Club root of cruciferous crops may be troublesome in lime-deficient soils; Conversely, potato scab is rarely a problem of more acidic mediums. Lime has most application in the vegetable garden but should not be overlooked elsewhere, such as in areas confined to fruitgrowing, and on lawns. The best • advice which can be given about liming is to have soil tests made of the various specific parts of the garden to determine their acidity (pH rating) and thus the need or otherwise for lime.

GARDENING

By

M. Lusty