Effect of farmyard manure on the trace element content of soils and of plants grown thereon

Farmyard manure, added to six soils at intervals over a two-year period until the equivalent of 240 tons of fresh manure per acre had been applied, significantly increased pH values, organic matter and nitrogen contents, water-soluble boron levels and total amounts of copper, zinc and molybdenum. The uptake of boron and manganese by ladino clover was less, and that of molybdenum was greater, on the manured than on the unmanured soils. It is suggested that the influence of manure on trace-element availability may be an indirect one, due to its effect on soil reaction rather than to any increased amount of these elements that may be added in the manure.Contribution No. 377, Chemistry Division, Science Service.