Harry F. Clements 467 



here, irrigations generally going on with tensiometer readings of 0.30 

 atmosphere. This schedule is maintained throughout the growing cycle 

 of the crop. 



When the young crop is between two and three months of age, its 

 plants are large enough to be sampled. Sampling is continued at 35-day 

 intervals throughout the two years of the crop. From these samples, 

 analyses are made for tissue moisture, nitrogen, potassium, phosphorus, 

 and total sugars. These data are plotted on the log. If all our early 

 operations, that is, weed control, irrigations, and fertilizations, have 

 been well timed and properly done, the moisture index is above 85, the 

 nitrogen index at or above 2 per cent, the primary index below 10 per 

 cent, and the potassium and phosphorus indices above the normal line. 

 These levels should be maintained throughout the first six months. 

 A second application of 75 pounds of nitrogen is made at three to four 

 months of age except in a few cases of high residual soil nitrogen. On 

 these, the nitrogen index remains high and the second application is 

 canceled. Occasionally, more nitrogen is applied if the index drops. 



If all the indices are maintained at these desirable levels, the growth 

 is excellent. Troubles may be encountered in maintaining the tissue 

 moisture level. If the soil was compacted by the harvest, the moisture 

 level of the next crop will drop even though irrigations are normal. 

 In short, anything which interferes with proper growth of roots will 

 result in the lowering of the moisture level and hence in the reduction 

 of growth. Here we have a few things which can be done. Since 

 nitrogen is a strong ally of moisture, we can apply small amounts of 

 nitrogen repeatedly, we can run smaller streams of irrigation water 

 down the furrows for a longer period of time, or we can insert trash 

 dams in the furrows to effect better penetration of water. Actually, at 

 best these are temporary expedients. It is usually best to correct such 

 difficulties when the field is plowed and planted. Accurate layouts of 

 irrigation furrows, incorporation of organic materials, and the selection 

 of a vigorous rooted variety all help to keep the moisture level up on 

 these soils. If the moisture level is low because of severe exposure to 

 winds, the selection of proper varieties is a considerable help. 



We know that maintaining the moisture level correctly results in 

 the production of heavy tonnage. To be sure, if the moisture level is 



