H.—34.

Table I shows that all the soils are well supplied with available phosphate, even in the subsoil samples. The potash figures show only a moderate status, with a tendency to decrease to a low level in the subsoil. With few exceptions the pH values of the soils are over 6-0 for the 0-6 in. depth; and in three cases the values are definitely greater than pH 7. These high values suggest that in certain cases alkalinity may be a detrimental factor in connection with tree-growth, since apples give optimum growth in the region pH 5-5-6-0. Under these -circumstances the aDr/lication of lime must be strongly discouraged. Sample 1013, with a pH value of 8-4, was taken from a peach orchard in which poor growth of trees occurred. In certain cases it appears probable that alkalinity of subsoil and substrata may likewise be unfavourable to apple-culture. Samples 1601 and 1602A-D illustrate the variations in pH values which may occur in the profile of a deep sandy silt type. On this soil trees were making rather poor growth. Samples 1605 and 1606A-D represent the profile of a good soil—that is, one which was associated with satisfactory tree-growth. In view of the high pH values and the semi-arid climate it was considered worth while to investigate the soluble salt content of typical soils, and in Table II are presented data relating to water-soluble salts in these soils.

Table II. —Water-soluble Salts. (All results expressed as percentages on oven-dry soil.)

Note.—C0 3 absent in all soils. In certain cases a high salt content is associated with alkaline soil conditions, but in at least one case (sample 1619) this correlation does not hold. In this instance the orchardist had pnt on ammonium sulphate recently, and in view of the high sulphate content of the sample it is understandable that high total salts are associated with a lowered pH. Where salts are high in the soil profile it is doubtful whether soluble nitrogen compounds such as the ammonium sulphate or sodium nitrate are the best forms of nitrogen to use on soils that are admittedly low in nitrogen. It may be that organic nitrogenous manures will prove much safer in use than the inorganic forms. In the former class must be included the growing of cover crops of leguminosse. It is difficult at this stage to express any definite opinion in regard to the effect of the different radicles present in the soils. Sodium carbonate (black alkali), which is very harmful to cultivated plants, has not been found in any of the samples. Mr. W. R. Lloyd Williams, Orchard Instructor at Alexandra, states, however (private communication), that he has seen patches of black alkali in the district, and this suggests that possibly the samples were not obtained at the best time for testing for this phenomenon. The sulphate figures shown in Table II vary greatly for different soils and for different depths in the profile. In certain cases the percentages approach 0-10 per cent., suggesting that " white alkali " (sodium sulphate) operates detrimentally in some orchards. The figures for chloride, with one exception, are low enough to suggest that chloride exercises only a minor effect on tree-growth. It is of interest to summarize the findings of other workers in connection with the adverse effect of soluble salts on plant-growth. Tsukunga (Proc. Inter. Gong. Soil Sci., 1928) states that 0-2 per cent, total salts impedes germination, while 0-09 per cent, is regarded as favourable, 0-14 per cent, intermediate, 0-33 per cent unfavourable, and 0-40 per cent, impossible to vegetable-growth. Later he states that an average SO 4 " content of 0-12 per cent. (0-04-0-17) is favourable to growth, while 0-7 per cent. (0-26-0-90) is unfavourable, but it is not made clear whether these concentrations are effective in the presence of other salts. _ Hilgard and Loughridge's (Univ. of Gal. Bull. 128, 133, revised) data is somewhat confusing, as they record Jonathans doing poorly on 0-041 per cent, total salts while Red Bietigheimers gave good results on 0-101 per cent, total salts. However, sodium carbonate appears to have been present in their soils, and it is difficult to assess how much of this effect was due to sulphates. G. W. Shaw (Gal. Exp. Sta. Bull, 119) records fair growth of beet with 0-127 per cent, total salts (0-004 per cent, carbonate), while poor progress was made where the total salts were 0-79 per cent." (0-039 per cent, carbonate).

B __H. 34.

57

Laboratory Depth J Locality . I Total 0aQ c| / S04 '. HC0 3 '. In. 1601 0-6 Alexandra 0-13 0-017 0-003 0-026 0-009 6-0 1602A 6-12 „ .. .. .. 0-116 0-018 0-003 0-028 0-009 5-2 1602B 12-18 „ .. .. .. 0-286 0-010 0-018 0-093 0-079 8-5 1602o 18-22 „ .. .. .. 0-238 0-008 0-015 0-057 0-075 8-6 1602D 24-28 „ .. ■■ 0-243 0-015 0-021 0-039 0-071 8-4 1603 0-6 „ .. .. •• 0-056 0-004 0-001 0-005 0-006 6-5 1605 0-6 Earnseleugh .. .. .. 0-098 0-010 0-004 0-013 0-008 6-9 1606\ 6-12 „ .. .. .. 0-028 0-004 0-002 0-009 0-006 6-1 1606b 12-18 „ .. •• 0-042 0-007 0-003 0-019 0-009 6-4 1606c 18-24 „ .. .. 0-056 0-004 0-002 0-004 0-012 6-4 1606D 24-33 „ .. •• 0-046 0-004 0-003 0-006 0-010 6-3 1607 0-6 .. .. •• 0-088 0-008 0-001 0-004 0-015 5-9 1609 0-6 Clyde .. .. .. 0-152 0-020 0-017 0-026 0-012 7-2 1611 0-6 Ripponvale .. .. .. 0-101 0-011 0-001 0-025 0-008 6-5 1613 0-6 Lowburn . . .. .. 0-075 0-009 0-0005 0-008 0-006 6-4 1615 0-6 „ .. •• •• 0-052 0-005 0-002 0-006 0-010 : 6-1 1617 0-6 „ .. •• 0-100 0-007 0-001 0-005 0-010 6-0 1619 0-6 Mutton Town Gully .. .. 0-233 0-045 0-002 0-072 0-010 5-5 1621 0-6 Earnseleugh . . " .. .. 0-073 0-006 0-001 0-005 0-008 6-2 1623 0-6 Cromwell .. .. •• 0-071 0-006 0-001 0-008 0-012 6-3