The Weed Herbage of a Slightly Acid Arable Soil

Abstract

The weed herbage was studied in the field on a light sandy loam of slightly acid character which has been under continuous wheat and barley cropping for over 50 yrs., with various manurial treatments up to 1926. Roughly half the year''s growth of plants had germinated before the end of April. A single year''s fallow was not very effective in getting rid of the weeds which had grown on this land; 2 years'' fallow brought about a fairly large reduction. Acidity of the soil induced by previous manuring with (NH4)2SO4 had a great influence and when the pH value was lower than 5 annual plants consisted almost entirely of Spergula arvensis, with a small amount of Polygonum aviculare and Poa annua. Matricaria inodora, though an acid-loving weed, disappeared almost entirely when the pH value was less than 5.4, but was also reduced in amount when it was greater than 5.8. Each of the weeds studied Seemed to have a definite range of pH value in which it was at its best. The effect of the long continued addition of mineral manures was very small. Annual addition of farmyard manure for 50 yrs. has left a legacy of an increased amount of most of the weeds. The effect of lime on the weed herbage was almost entirely governed by the change in acidity thereby induced. Perennial weeds becoming important were:[long dash](a) Holcus mollis and Agrostis stolonifera, serious in the more acid plots, but almost eradicated by 2-year fallow, (6) Rumex acetosella also in the more acid plots not removed by a fallow of 2 years, (c) Equisetum arvense, encouraged by the fallowing of the land, but absent from the more acid plots. Tussilago farfara appeared to be indifferent to the previous treatment of the land, but entirely disappeared after the fallowing operation.