Experiments on the continuous growth of arable crops at Rothamsted and Woburn-Experimental-Stations - effects of treatments on crop yields and soil analyses and recent modifications in purpose and design

This paper describes six field experiments started during 1843-77. All, with various modifications, still continue and results for various periods between 1843 and 1975 are given. Originally the experiments investigated the nutrient requirements of wheat, barley and root crops, each crop grown in monoculture. Yields on unmanured and farmyard manure treated soils were measured and compared with those given by N P K Na Mg Si supplied in inorganic compounds and tested singly and in various combinations. These experiments soon demonstrated that fertilisers could give the same yields as farmyard manure and showed the relative importance of N, and K for the various crops.
All manures tested supplied more nutrients than were removed in the crops. Nearly all the fertiliser N residues have been lost from the soil.; some N has accumulated in soils given farmyard manure but even on these soils much has been lost. Most of the P residues have remained in the plough layer but some K has moved into the subsoil. The P and K residues can be detected by increases in the bicarbonate soluble-P and the exchangeable K but neither method of soil analysis gives an estimate of the total amount of plant available P and K in the soil. However, field experiments shows that residues are available to a wide range of crops. In some comparisons yields were always better on soils with residues than on those without, even when much new fertiliser was tested.
Soils which have received annual dressings of farmyard manure for more than 100 years now contain more organic matter than soils with fertilisers only. During recent years varieties with a high yield potential, and improved cultural techniques, including weed, pest and disease control have been introduced. in this period yields of root crops and cereals grown in rotation have been larger on farmyard manure-than on fertiliser-treated soils. This difference cannot be explained in terms of spring applied fertiliser N dressings; further investigations are being undertaken.
RESP-07570