Early Experiments on Wheat at Holkham. 7 



resource of constituents, and probably the power of absorp- 

 tion or retention of mammal matter also, of the so-called 

 heavy soils. But it was of the greatest interest to ascertain 

 by actual experiment how far those chemical substances, 

 which are employed with success for the increased growth of 

 wheat upon heavy soils, could be used with advantage upon 

 those of different descriptions. 



Previous to the introduction of the four-course system by 

 the late Earl of Leicester, the soil upon which the experiments 

 were made had been considered too light to grow wheat. 

 The land had for some years previous to the experiments been 

 farmed under that system ; it was clayed about twelve years 

 before the experiments were begun, and the crop immediately 

 preceding them was white turnips, manured with farmyard 

 dung and guano, both tops and roots being drawn off the 

 land. The experimental plots measured half an acre each ; 

 the manures were as follows, and were all sown in the 

 autumn, except plot 4, which was sown in spring : 



Plot 1. Always unmanured. 



Plot 2. Mineral manures alone. 



Plot 3. Ammonia-salts alone, sown in the autumn. 



Plot 4. Ammonia-salts alone, sown in the spring. 



Plot 5. Both the mineral manure and ammonia-salts. 



Plot 6. Rape cake. 



Plot 7. Farmyard manure. 



1. The unmanured plot, when once exhausted of the 

 accumulations derived from the more recent previous 

 manuring, would, of course, show the productive capability of 

 the soil in a comparatively normal state, in conjunction with 

 that of the annual climatic yield of the atmospheric elements 

 of growth ; and the results would provide a standard with 

 which to compare the produce of the different manures. 



2. The mineral manure furnished a liberal supply of the 

 alkalies (potash and soda), alkaline earths (lime and 

 magnesia), and phosphoric acid ; and its produce, compared 

 with that of the other plots, shows whether the result of the 



