In a series of field experiments from 1966 to 1969, on light sandy loam soils in the West Midlands, comparisons were made between two levels of application of herbicides based on urea, triazine and bipyridil compounds for weed control in early potatoes.

Under conditions of adequate nutrient and water supply, the high application rate controlled about 94%, and the low application rate about 88% of the annual weeds. At equivalent application rates, urea compounds and herbicide mixtures containing ureas, gave superior weed control to triazine compounds and herbicide mixtures containing triazines, but the ureas were apparently more phytotoxic to the potatoes.

In 1970, comparisons were made between three levels of application of ametryne and monolinuron, high, medium and low and an unsprayed control treatment.

The highest yields of potatoes were associated with the low application rates of herbicides from 1966 to 1970.

It was concluded that, on these light sandy loam soils, when irrigation is available, relatively low application rates of either monolinuron or ametryne, or mixtures of ureas or of triazines, or mixtures of bipyridils and ureas or triazines could give adequate control of annual weeds in early potatoes at low cost.