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<br />00\)0'1 \ <br />through most of the soil profile). Special care would be required to avoid local accumulations of <br />salinity in the vicinity of the seedling in order to obtain a good stand. The SAR is also sufficiently <br />high to cause degradation of soil tilth-crusting, reduced permeability, hard/compact clods, etc.-- <br />especially after rains or inigations with dilute waters. Parts of the field have considerably higher <br />levels of salinity and SAR than the mean values (see Tables 2 & 6 and Figure 7). Hence, the salt- <br />related problems in these "higher" areas would be even greater than for the average area. This <br />field is subject to the additive effects of two other problems because it is inigated by sprinklers. <br />One is the foliar uptake of salts and the resulting toxicity and "burning" that occurs when the <br />water applied is as high ( 2500-6000 ppm) as it is in the well waters used on this field. This will <br />especially be a problem if these saline waters are applied to the plants in their very early growth <br />stage (emerging seedlings) when they are very susceptable in this regard. The young plants can be <br />literally killed under such conditions, especially when the soil is so saline, as well as the inigation- <br />water. A second is the enhanced loss of tilth caused by the impact of water falling upon the <br />topsoil. This extra physical-energy adds to that caused by the chemical-energy forces (those <br />associated with high SAR and low salinity) which cause aggregate failure, soil crsting, etc. Thus, I <br />would expect substantial problems of stand establislunent in this field caused by the combination <br />of high soil salinity, high water salinity and high soil sodicity. Obviously, without stand, crop <br />production can not be achieved. <br /> <br />Average soil salinity levels (about 4.5-6.0) in field #3 are low enough to be able to grow <br />wheat and other crops of moderate or greater salt-tolerance, provided stand can be established. <br />The SAR, especially in the topsoil, is sufficiently low (4) to not expect substantial tilth problems <br />in the field, iff alling-water impact and excessive & too-wet tillage are avoided. Of the four fields <br />that we examined during the trip, this field has the lowest levels of salinity and sodicity. <br />Apparently, the water used to inigate this field is of better quality. Results are given in Tables 4 & <br />7. <br /> <br />Average soil salinity and sodicity levels (about 7-12 in EC, and about 14-23 in SAR) are <br />higher, more variable and more limiting to crop production in field #4 than in the other three <br />fields(see Tables 4 & 7 and Figures 8 & 9). For example, a value of-15 mmho/cm was measured <br />in one of the 0-30 cm. soil samples and as high as 22 mmho/cm in one of the 60-90 cm. soil <br />samples. An SAR of35.7 was measured in one of the 0-30 cm. soil samples. Thus, one can expect <br />some areas of this field to be essentially incapable of conventional crop production. These areas <br />are shown in Figures 8 & 9 (Figure 9 was created from the mobile, four-electrode tractor <br />measurements). I suspect the source of the problem here is related to the uneven microrelief and <br />differences in soil texture, but possibly also to a shallow water table. We didn't collect data in this <br />regard. You will see in Table 4 and in Figure 4 that there is a fair correlation between EC, and SP <br />in this field. Since the salinity increases with depth in essentially all of the soil profiles sampled in <br />the field, including those with high salinity levels, I conclude that the net flux of water is <br />downward everywhere in the field--thus, the high levels of salinity are not likely caused directly by <br />the upflux of water and salts from the water table. Rather the areas of high salinity seem to be <br />resulting from inadequate leaching in these areas, which may be because the soil is less permeable <br />in these areas--either because of higher clay cOntent or poorer drainage conditions--or because the <br />farmer is underinigating or the uniformity of the inigation-system is very poor. The analyses of <br />the three well water samples the farmer of this field gave me are shown at the bottom of page 6 of <br />the analytical results table. These waters are saline enough to have produced the higWy salt- <br />affected conditions found in parts of this field only if the leaching fraction in these areas is very <br />low (about 5% or less, see the enclosed W ATSUIT printouts). <br /> <br />,'\ <br /> <br />"1 <br />