YIELD 



427 



Zavitz carried out experiments with large and small wheat grains for 

 six years with winter wheats and eight years with spring wheats, and 

 found an average annual increase of 6-5 bushels per acre from large as 

 compared with small grains in the winter wheats, and 3-7 bushels increase 

 in the spring wheats. 



Similar pre-eminence of large over small seed grain has been observed 

 by others. 



The plants from small grain are weak, and many succumb to the 

 adverse soil and climatic conditions of autumn and winter. 



In a few exceptional instances, where the land has been in a specially 

 high condition, small seed grain has given remunerative results almost 

 equal to those in which larger seed has been sown ; nevertheless the 

 inferiority of small grain as seed is always strikingly evident when its 

 yields are compared with those from large grain upon soil in compara- 

 tively poor condition. 



Number of Grains sown.-^- The number of grains in a bushel (63 Ibs.) 

 of Bread Wheat varies between 500,000 and 800,000. 



In the former case the grains are large, 100 weighing 5-71 grams, 100 

 of the latter weighing 3-57 grams. The number of grains in a bushel of 

 wheat of the type usually grown in this country is about 650,000, 100 

 weighing 4-4 grams. 



From the following table it is seen that when one bushel of an average 

 sample is used there are sown about 134 grains per square yard, the rate 

 when 3 bushels are sown being 392 per square yard. 



NUMBER OF GRAINS SOWN PER ACRE 

 (100 grains = 4-4 grams). 



Even under favourable conditions the number of plants which appear 

 above ground after sowing these amounts of grain are generally 5-10 per 

 cent less than the figures quoted, since the germinating capacity of the 

 seed wheat is usually not more than 90-95 per cent. 



Not infrequently 15-30 per cent of the plants which are seen soon 

 after the seed germinates disappear later. This decrease is due to de- 

 struction by birds, insects, and fungi, as well as by frost and adverse con- 

 ditions of the soil. Some of the loss is also brought about by competition 



