98 



MISCELLANEOUS PUBLICATION NO. 1065, U.S. DEPARTMENT OF AGRICULTURE 



the energy state of water in soils, research on water 

 retention and movement can be and must be 

 expedited. 



Genetic lines of many crops vary greatly in their 

 response to saline and sodic soils. Indications of 

 this variability have been found in cotton, cereal 

 grains, grasses, and fruits. Plant breeding research 

 to develop lines with superior salt and alkalinity 

 tolerance should be expedited. 



Far more definitive information is needed on the 

 biochemical and physiological mechanisms in 

 plants that determine their tolerance to various 

 salt-affected soils. Unfortunately, little informa- 

 tion is available on the effect of climatic condi- 

 tions in modifying inherent salt tolerance of crops. 

 Such information is essential to crop and soil 

 management in soils subject to salinization. In- 

 creased knowledge of salt rejection by biological 

 membranes could be extremely helpful in desalt- 

 ing sea water. It is also essential to plant breeders 

 working to develop varieties and strains with 

 higher salt tolerance. 



Fence lines sometimes show AAdde differences in 

 salinity damage. Even with identical water supply, 

 identical soil, and identical crops, diverse manage- 

 ment practices by different operators on either side 

 of the fence may be the difference between success 

 and failure. Accordingly, much better practical in- 

 formation is needed to unerringly predict the 

 combination of management practices for maxi- 

 mum production efficiency under a given set of 

 conditions pertaining to salty soils or waters. 



Hard experience in the Western States has re- 

 vealed that successful irrigation requires effective 

 drainage. Accumulating salts must be continually 

 leached out. This is the only practical means 

 known today for maintenance of irrigated agricul- 

 ture in many areas and for reclamation of areas 

 already salted out. Excess leaching Avastes water 

 and plant nutrients. For most efficient use of water 

 and maintenance of a favorable salt balance in the 

 fields, better mathematical expressions are urgently 

 needed for the calculation of leaching require- 

 ments, drainage requirements, and the proper salt 

 balance. 



Fields and irrigated areas already seriously im- 

 paired by salinity must be treated with the most 

 economic reclamation procedures available. It is 

 essential that more research attention be given to 

 minimizing the cost of amelioration procedures on 



salinized lands for redeveloping productive soil- 

 water-plant systems. 



The return flow from an irrigated area is almost 

 invariably saltier than the incoming water. The 

 salt that comes in must go out, but part of the 

 water carrying the salt in is lost in evapotranspira- 

 tion from the field. Hence, Nature's principles dic- 

 tate that there be a corresponding concentration of 

 salt in the outflow water. If the drainage return 

 flow enters a stream, the downstream users accuse 

 the irrigation project for contaminating the 

 water. One of the most pressing needs for infor- 

 mation in irrigation agriculture is the development 

 and evaluation of other procedures for disposal or 

 reclamation of return flow — procedures that seek 

 to maximize beneficial use of total water available, 

 while minimizing contamination for downstream 

 users. 



Experience has already shown that one of the 

 prime contributions the United States can make in 

 the Food for Peace Program is sound technical in- 

 formation on the management of salt-affected soils 

 in the irrigated areas of the world. 



Organic Wastes 



It is most fortunate for 20th century man that 

 there were conditions in prehistoric times under 

 which a vast production of organic wastes from 

 prolific vegetation was not completely oxidized, 

 but accumulated under water as muck and peat 

 to become a wealth of coal and oil eons later. 



It is most fortunate for 20th century man that 

 there are conditions now by which a vast produc- 

 tion of organic wastes is rather rapidly oxidized 

 by bacterial activity, conflagration, or other means 

 back to C0 2 and H 2 0. Our problems with organic 

 wastes arise because oxidation does not take place 

 as rapidly or as acceptably as we would like. 



New, more extensive, or more useful information 

 is needed on the production, handling, and dis- 

 posal of organic wastes, including animal wastes, 

 reclaimed sewage effluent, crop residues, forest 

 slash, and processing effluent. 



Animal Wastes 



Production of farm animals has become big 

 business. There are highly mechanized dairies car- 

 rying 400 head ; f eedlot operations handling 10,000 

 cattle; and automated poultry enterprises caring 

 for 100,000 fowl. An operation involving 400 milk 



