H.—34.

Linen-flax Soils. A survey of the soils that have grown linen flax in the past season was commenced in February, 1941. Very little was known of the soil requirements of linen, flax grown under the' conditions existing in this part of New Zealand, and it was necessary to make a fairly full examination of numerous individual crops in order to assess the part played by the soil and other factors which were mainly agricultural (cultivation, previous cropping, fertilizer applications, &c.,) but also included aspect, shelter, local rainfall, &c. This latter stage of the investigation was greatly facilitated by the Agricultural Instructors, who were able to point out where the agricultural practice was affecting the growth of the crop. The object of the survey is to provide a soil map of each flaxgrowing district showing in particular which of the soils are likely to be suitable for flax. Detailed mapping is practically completed in the Balclutha and Clydevale districts. The main soil factors that adversely affected the flax crop during the past season in South Otago and Southland are —■ (1) Shallow silt loams and sandy loams overlying river shingle. When the shingle approached to within 15 in. of the surface the flax crops were very uncertain. A few succeeded, but the great majority ripened without making sufficient length of fibre. In the case of loam and clay loam topsoils overlying shingle, the critical shallowness of the soil was in the region of 12 in. These soils are locally regarded as being very suitable for wheat and oats, but this is a case where good cereal land is not the same as good flax land : (2) Shallow and stony soils over rock. The unsuitability of these soils was due obviously to insufficient moisture-holding capacity in the topsoil and the absence of a moisture reserve in the subsoil: (3) Stony soils developed on fan debris formed by mountain torrents. This type of soil accounted for most of the failures in the Crookston district: (4) Soils on the rolling hills at an altitude of 1,000 ft. above sea-level. Here the main factor is probably exposure. The soil itself does not appear to be unsuitable : (5) Soils on the steeper slopes of the rolling hill country. Sheet erosion has reduced the depth of the silt loam topsoil, and when the slopes are ploughed the heavier-textured subsoil is brought to the surface. This subsoil is not only poorer in. plant foods, but it is less easy to break down and consolidate prior to seeding : (6) Heavier-textured soils in general. This again, is probably an agricultural problem and concerned with the difficulty of getting heavy-textured soils into a fine enough tilth, particularly when ploughing is delayed until the spring. Soil Survey Laboratory, Wellington. General Soil Survey.—The general soil survey of the North Island has absorbed most of the energies of the chemists and no time has been available for the research side of soil work. For the general survey the following estimations are made on all samples : Available phosphate and potash, pH, carbon, nitrogen, base exchange capacity, total exchangeable bases, percentage base saturation, replaceable calcium and magnesium together with texture analyses, carbonate, and soluble salts contents as required. These data give a fairly complete picture of the soil's likely performance. Over a thousand soils have been examined on these lines, and the results have contributed in no small degree to the reliability of the North. Island soil map. The North Island analyses are practically completed, and a start has been made on South Island soils. Justification for the survey can be found in the variations that occur between different soil types. For instance, citric-acid-soluble phosphate values have ranged from less than 0-001 to 0-10 per cent., potash from 0-009 to 0-21 per cent., pH from 4-1 to 8-1, carbon from 1-2 to 62-3 per cent., nitrogen from 0-06 to 1-92 per cent., carbon-nitrogen from 10 to 50, base exchange capacity from 3-9 to 113 m.e. per cent., total exchangeable bases from 0-09 to 58 m.e. per cent., percentage base saturation from 1 to 100 per cent., exchangeable calcium from 0-6 to 56 m.e. per cent., magnesium from 0-1 to 20-9 m.e. per cent., and soluble salts have been found up to 0-4 per cent. The main groups found in the North Island survey have been mentioned elsewhere in this report, and in passing it can be said that podsols mapped in the field conform in. chemical data to their usual characteristics. Brown loams have a lower acidity than their percentage base saturation would indicate. Brown granular clays tend to show higher than usual magnesium compared with calcium on the maturer soils, and the yellow-grey group, although exhibiting a definite profile, is not strongly leached, percentage base saturation often being of the order of 60 per cent. Glauconite as a Possible Potash Fertilizer. —Samples of glauconite greensand were examined from the viewpoint of their suitably as a source of potash. Analyses showed that the availability of potash, in these samples was little different from that of a good, soil, and no hope could be held out at present for its use in its natural condition. Treatment with heat, and sodium chloride did increase potash availability, but the cost of processing would be prohibitive when other sources of supply are considered. Effect of Continuous Superphosphate Manuring on Outgo of Magnesium and Potash in the Waikato.—A number of soil samples from untop-drossed areas and from fields top-dressed mainly with superphosphate in a manner which would be considered normal for the Waikato have been analysed. The analyses showed that while the lime and phosphate level had been built' up as the result of top-dressing there were decreased amounts of potash and magnesium present in the soil, indicating that the present system of Waikato top-dressing in an unbalanced one. From the analyses it was concluded that gypsum contained in commercial superphosphate was likely to be the main

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