46 



THE ESSEX EXPERIMENTS 



The relative position of the two types of phosphate during the 

 wet seasons is curious. At Martin's Hearne the rock phosphate has 

 a decided advantage. It also does a trifle better at Latchingdon, but 

 the advantage is so small as to be well within the limits of experi- 

 mental error. 



The results at Lambourne End (Table XVIII) for the dry season 

 of 1919 and the moist season of 1920 fully bear out the results recorded 

 above. 



The soil at Martin's Hearne has considerably more organic matter 

 in it than the soil at Latchingdon. Moreover it is a ' sour ' soil, with 

 a lime requirement of -27 %, whilst the soil at Latchingdon has a 



TABLE XX. EFFECT OF RAINFALL ON THE AVAILABILITY 

 OF ROCK PHOSPHATES 



Dry seasons, 1917 and 1919. 



Martin's Hearne 

 Latchingdon 



24-3 

 23-7 



28-7 

 30-1 



4-4 

 6-4 



4-06 

 3-74 



27 

 03 



Moist seasons, 1916, 1918 and 1920. 



small reserve of calcium carbonate and has only a negligible lime 

 requirement. It would seem therefore that, on ' sour ' soils well sup- 

 plied with organic matter and situated in districts with a moderately 

 high rainfall, rock phosphates may give even superior results to 

 those secured from basic slag. 



In Table XXI the average returns from rock phosphates and basic 

 Bessemer slag on the 'sour' soils are contrasted with the corresponding 

 results from those centres where the soil is 'sweet,' that is, has a 

 reserve of calcium carbonate and no lime requirement. 



The differences, although small, are probably real. The figures for 

 Martin's Hearne, for example, are compiled from four rock phosphate 

 plots over a period of four years, for Lambourne End from five rock 

 phosphate plots over a period of two years, and two high soluble 

 slags over a similar period. Those for Latchingdon and Saffron Walden 

 represent one rock phosphate plot and one basic Bessemer slag plot 



