166 IRRIGATION PRACTICE 



In general, much water produces at first leafy plants; 

 if more is added, the proportion is diminished. Crops 

 grown for forage, in which a high proportion of leaves is 

 desirable, may profitably be given larger quantities of 

 water than crops that are grown more largely for some 

 other part of the plant. 



108. Proportion of heads and grain. The grain 

 crops are grown primarily for seed. The value of the 

 straw is small in comparison with that of the seed. The 

 grain farmer desires therefore to convert as much as pos- 

 sible of the plant into seed at the time of harvest. Up 

 to a definite limit, the clusters of seed-bearing heads 

 increase with the quantity of water used. The number 

 of seeds in each head of wheat, or ear of corn increases, 

 likewise, as the quantity of water is increased. Even 

 the beard in the bearded varieties, becomes longer or 

 shorter as much or little water is applied. The seed- 

 bearing part of plants, like the roots, stalks and leaves, is 

 sensitive to the water applied to the soil. 



Many reported experiments deal with the proportions 

 of the heads in grain crops as influenced by varying 

 quantities of water. In the Utah experiments it was 

 found that as the total quantity of irrigation water was 

 increased the proportion of heads in the plant above 

 ground decreased with wheat, from 38 to 25 per cent; 

 with oats, from 59 to 49 per cent; with peas, from 67 to 

 48 per cent. In every case it was distinctly shown that 

 the more water applied, the smaller the proportion of 

 the heads in the whole plant. Therefore, while the size 

 and number of heads seem to be increased as the total 

 quantity of water increases, it is equally clear that the 

 stems and leaves are increased more markedly. This 

 leads to a decreasing proportion of heads in the whole 



