MANURES AND WEEDS

Nelson Evening Mail, Volume LXIV, 10 January 1931, Page 10

MANURES AND WEEDS

EFFECTS OF LIME Dr. Winifred E. Brenchloy. dealing with tho influences of fertilisers on meadow hay. showed that fertilisers exercise an indirect, as well as direct action on yield on grass and arable land by influencing the growth of plants other than the desired crop, so varying the,degree, of competition to which"the crop, is, subjected. The composition of weeds or undesirable plants is a much more important factor ir. determining yield- than is generally recognised. Op .arable land the "type of manuring chat is favourable to good crop production, also favours the growth of weeds. If seasonable conditions encourage the germination and growth of weed seeds before the crop makes headway, tho competition causes serious reduction of crop yield, which is frequently more

marked with heavy than with light manuring. The potential weed flora may be very abundant, quantitative experiments at Rothamsted showing that the numbor of viablo weed seeds buried in the soil may run into hundreds of millions per acre.with certain types of fertilisers.

On grassland the effect of artificial fertilisers is variously influenced by liming. On heavy land long-continued treatment with sulphate of ammonia and minerals tend to produce acid soil conditions, and the production of a herbage composed of the less desirable grasses and giving relatively low yielj. Liming under these conditions increases yield greatly, and changes the balance of composition in favour of more desirable species. On the other hand, oh the same soil liming has much less or no beneficial effect with one-sided manures, such as superphosphate alone, or where tho soil is tending toward an alkaline reaction due to the use of nitrate of soda and minerals.