INCREASED CROP PRODUCTION 105 



potash. Chemistry has also shown how to use them 

 to the best advantage, so that crop growth is now 

 possible with only a few hundredweights per acre 

 of salts that would otherwise necessitate ten or more 

 tons of farmyard manure. 



Manures and fertilizers not only act as nutrients, 

 but also as means of modifying the environment. 

 Thus organic matter considerably alters the texture 

 of the soil and its power of holding water, so that a 

 plot treated with farmyard manure tends to be moister 

 than an untreated one. Phosphates not only serve 

 for the nourishment of the plant, but they also facili- 

 tate root development: they are therefore particularly 

 useful in conditions where roots naturally cannot 

 grow well, e.g. on heavy clay soils. Further, they 

 facilitate the early stages of plant growth and hasten 

 maturation, thus adding to their value on heavy land. 

 Potassium salts tend to lengthen the life of the plant, 

 and are therefore useful on light sandy soils where 

 growth tends to finish early. These effects are not 

 very great so far as yield goes, but they make a 

 considerable difference to the certainty of a harvest 

 and to the ease and cost of growing the crop. 



Perhaps the main direction in which improvement 

 is possible is the poor grass-land, and this because, 

 when it was formed, it was usually considered too 

 poor to be arable land. Over large areas of boulder- 

 clay basic slag effects a remarkable improvement, 

 especially when wild white clover seed is sown as 

 well. Undoubtedly we. could greatly increase the 

 produce of our grass-land by this method, and it is 

 being done. It thus becomes possible to maintain 

 our present head of stock on a smaller area of grass 

 and to liberate extra grass for ploughing up. 



The British farmer quite understands these points, 

 and he uses a great deal of the various fertilizers: no 



