MOLYBDENUM on New Zealand Soils

New Zealand Journal of Agriculture, Volume 95, Issue 2, 15 August 1957, Page 173

MOLYBDENUM on New Zealand Soils

Basalt and Andesite Rock Soils of Auckland Province

THAT the application of molybdenum might be of value in New Zealand was first suggested by E. B. Davies, Senior Chemist, Department of Agriculture's Rukuhia Soil Research Station, when he found in 1945 that whiptail disease of cauliflowers noticed in a Wellington suburb was associated with a deficiency of molybdenum (I). Subsequently experiments were laid down in pastures on nearly all major soil types, with the result that knowledge of the distribution of molybdenum-deficient soils is now far advanced. In this article, the second of a series which will appear periodically in the "Journal", N. A. Clarke, formerly Instructor in Agriculture, Department of Agriculture, Kaikohe, and H. G. B. Halliwell, Instructor in Agriculture, Department of Agriculture, Kaitaia, discuss molybdenum requirements of Auckland Province soils derived from basalt, andesite, and dolerite. The first article, in the July issue of the "Journal", dealt with Auckland Province soils derived from sandstone, mudstone, and limestone.

THE soils derived from basalt are popularly known as volcanic soils. As the older and most leached of these are prominent because of the accumulation of iron nodules in the subsoils, they are popularly known as ironstone soils. The soils derived from andesitic rock flows and steep formations of doleritic rock are popularly known as semivolcanic soils. In this article the value of molybdenum will be discussed on a soil type basis, . beginning with semivolcanic soils and followed by volcanic and ironstone soils. Semi-volcanic Soils More accurately the semi-volcanic soils are described by the Soil Bureau,

Department of Scientific and Industrial Research, as brown granular loams and clays. They are brown soils derived in a few instances from dolerite rock, but most commonly from andesitic rock flows and from alluvia derived from andesitic material. Semi-volcanic soils are located in large blocks east of Kaitaia from Doubtless Bay to Whangaroa Harbour. They are also present as blocks in the Te Kao and Te Paki areas in the far north. South of Kaitaia they form the Mangamuka Ranges. South of Kaikohe there is an area of semivolcanic country of about 300,000 acres. This area is bounded by Tautoro and Waipoua Forest to the north and Kaihu and Parakao to the south. Several ranges running from north to south dissect the area into a number of valleys. The elevation mostly varies from 550 ft. to 1100 ft., but rises to nearly 2000 ft. in Waipoua Forest. Rivers fed by these bush-clad, andesitic ranges have deposited volcanic material in alluvial flats and terraces. For instance, the soils of the Kaitaia flats contain much andesitic material. The brown granular clays and loams cover quite a large area, about 600,000 acres in all, of which 100,000 acres are easy rolling, 300,000 acres are medium steep, and 200,000 acres are very steep and of little potential value for farming. The easy rolling soils (Rangiuru, Awarua, and Aranga clays) have long puzzled farmers and agriculturists because of their, infertility and because they defied worthwhile development by the orthodox means of applying superphosphate, lime, and potash. The pastures quickly reverted to dominant browntop-danthonia swards practically devoid of clover and capable of carrying about J sheep to the acre. Only heavy dressings of lime, particularly if combined with applications of basic slag, produced reasonable pastures. With present knowledge facts such as these point to molybdenum .deficiency, and it is therefore not surprising that in experiments and later in practice this trace element has given outstanding results on almost all soils derived from andesitic parent material. In many cases the. use of molybdenum combined with superphosphate and some lime and perhaps potash may double or even treble carrying capacity. The sheep-carrying capacity in certain paddocks on these soils has already been trebled with one application of molybdenum. On one farm butterfat production has increased from 10,5001 b. to 21,0001 b. in 1 year with the same number of cows. Another farmer, in the Awarua district with the help of molybdenum and pasture oversowing last season milked 75 cows on 250 acres with a winter run-off on part of a farm which previously ran 200 sheep and about 40 Polled Angus cattle on 1000 acres. Thus districts regarded until now as containing only submarginal land, largely reverted to scrub, can now be developed economically into thriving centres of fat lamb or even dairy production. On Coromandel Peninsula outstanding responses to molybdenum on semi-volcanic soils have also been obtained.

The rate at which molybdenum should be applied on the semi-volcanic soils of North Auckland and Coromandel is not exactly known. Sodium molybdate at 2|oz. per acre has given good results in all but one field experiment. In spite of the good response to molybdenum, the use of lime is still recommended, but the very heavy rates previously considered essential to produce good pastures are now thought to be unnecessary. The use of lime on the steeper, immature soils is limited by their topography (for instance, Te Kie stony loam); these soils, however, are not very acid. The same may apply to soils derived from recent alluvia. On the more mature soils of the easier slopes lOcwt. to 15cwt. of lime and 2|oz. to soz. of sodium molybdate per acre is now

recommended instead of the 2 to 3 tons of lime per acre favoured previously. Molybdenum responses on the brown granular clays have also been observed on swedes, turnips, chou moellier, rape, com, and pumpkins. Swedes of up to 191 b. have been grown on a field sown with molybdenum superphosphate when broken in from virgin country. Nevertheless, the use of a nitrogenous fertiliser in addition to molybdenised superphosphate on swedes and other crops may have merit on some of the poorer northern soils. Molybdenum does not reduce the need for nitrogenous fertilisers. The semi-volcanic soils respond somewhat characteristically to molybdenum. The usual pattern is a marked initial increase in the growth of clovers, either as trefoil, Lotus uligin-

osus (major), subterranean clover, or red clover and white clover, depending on fertility levels and species grown previously. However, ultimately the sward becomes white clover dominant and eventually perennial ryegrass will become prominent if originally present in an unthrifty form. Palatability of the topdressed area increases and stock graze preferentially the treated areas. This increase in palatability is often the first sign of - a molybdenum response. Effect on Stock Health Pastures of brown granular loams and alluvia derived from andesitic parent material have a satisfactory copper content (7 to 13 parts per million of dry matter) (2) and a low molybdenum content (usually less than

1 p.p.mj. On the results available so far topdressing with 2|oz. or soz. of sodium molybdate per acre has not raised the molybdenum content of pastures much above 1 p.p.m. Five ounces of sodium molybdate is equivalent to the molybdenum content of 6cwt. of molybdenised superphosphate. One word of warning, however, is necessary. It has been shown by Dr. I. J. Cunningham that immediately after the application of molybdenum the amount of this element in the herbage may rise steeply and fall gradually a few months after application. The Department of Agriculture has no information on molybdenum levels of pasture a few weeks or months after application. For this reason, even on these relatively “safe” soils farmers are cautioned not to use more molybdenum than is necessary to obtain optimum growth. Volcanic Soils The so-called volcanic soils are derived from basalt and basaltic scoria. Fairly large areas occur north and west of Whangarei and south and east of Kaikohe. The citrus orchards of Kerikeri are situated on the more leached and mature soils of this group.

MORE IMPORTANT SOIL TYPES AND THEIR REACTIONS TO MOLYBDENUM

Soli type Topography Semi-volcanic soils Mangakahia loam Flat Kai tala clay loam Flat Awarua clay i Rangiuru clay i Easy rolling Pakotai clay 1 Kohumaru clay Mainly flat Tutamoe clay I ' Aranga clay i Undulating Mangonui clay Rolling ' Waimatenui clay Rolling Waimamuku bouldery Rolling to hilly clay (complex) Onetai clays and Rolling to hilly loams (complex) VVhatoro clay Easy rolling Takitu clay > Mainlv hiUv Katui clay i Malnly nill -' Awapuku clay Rolling to hilly Te Kie (red brown Hilly to steep phase) Volcanic soils (derived from basalt) Kerikeri friable clay Gently undulating Taraire friable clay Gently undulating Ruatangata friable clay Undulating Ironstone soils Okaihau friable clay Gently undulating

Reactions No experiments, but paddock trials have shown response (recent alluvium). Good molybdenum responses. May need soz. of sodium molybdate per acre. Generally it is about 10 months before responses show, but this may depend. on time of application of sodium molybdate in relation to the beginning of spring clover growth Excellent response to molybdenum. Appear to need soz. of sodium molybdate per acre initially. Excellent response to molybdenum. No experiments, but good response to molybdenum is probable. Excellent response to molybdenum. Excellent response to molybdenum. Appears to need soz. of sodium molybdate per acre initially. ' Good response to molybdenum. Fair response to molybdenum Excellent response to 2%0z. of sodium molybdate per acre in one trial. Much reverted to scrub. Not enough experiments, but molybdenum responses are likely. Excellent responses to molybdenum, but about 12 months may elapse after the application of molybdenum superphosphate before responses show, particularly on poor, sodbound paspalum. May require soz. of sodium molybdate per acre. Excellent response to molybdenum. May need soz. of sodium molybdate per acre for best results. Very slight pasture responses. Very slight pasture responses. Very slight pasture responses. Very slight pasture responses.

Pastures on the soils found at Kerikeri (Kerikeri clay loam) and pastures on a small number of other soil types which are fairly leached (about 30,000 acres) are responding very slightly to molybdenum, but the comparatively small effect of molybdenum on these soils and the fact that major improvement can be effected with phosphate, lime, and potash has not encouraged the use of molybdenum. The levels of copper in the herbage of pastures on these volcanic soils derived from basalt seem satisfactory (2), with an average of about 10 p.p.m. of dry matter. The molybdenum content of untreated pastures is low. usually below 1 p.p.m. Ironstone Soils -f’ The ironstone soils are derived from the same parent material (basalt) as the so-called volcanic soils. Greater age, however, has led to more severe leaching and to the gradual formation of iron nodules, giving, in extreme cases, a soil of gravelly appearance (Okaihau gravelly clay). The only large block of ironstone soils (about 70,000 acres) occurs west and north-west of the Bay of Islands.

The Department of Lands and Survey and private farmers have broken in a considerable proportion of it in the last few years. Experiments with molybdenum have shown slight increases in the growth of pastures. If lime, superphosphate, and potash are applied at the recommended rates, however, the use of molybdenum does not give much improvement. Pasture copper levels on the ironstone soils are satisfactory if somewhat variable, ranging from 6 to 12 p.p.m. of dry matter in 20 samples examined (2). Molybdenum levels of untreated pastures are very low Summary Pastures and crops on nearly all the soils derived from andesitic parent material gave outstanding responses to molybdenum. The use of up to soz. of sodium molybdate per acre (as contained in 6cwt. of molybdenised superphosphate) is recommended, but no more is advised. No adverse effects on stock health are expected after the recommended rate of application, except perhaps where there has been very heavy liming in the past. Though pastures on a number of soils derived from basalt do respond slightly to molybdenum, its use is of

relatively slight benefit on wellmanured fields. Further, the regular use of molybdenum on this group of soils (Kerikeri clay loam, Ruatangata friable clay, and Okaihau friable clay) could lead to stock poisoning unless copper is applied to counteract the toxic effects of molybdenum. - REFERENCES 1. E. B. Davies, “Nature”, vol. 156, page 392, 1945. 2. I. J. Cunningham, unpublished data.

Main Wool Sales The dates and venues of main wool sales until the end of 1957 are: 23 and 25 October: Dunedin. 30 October: Christchurch. 8 November: Auckland. 13 November: Wanganui. 18 and 20 November: Napier. 25 November: Wellington. 4 December: Christchurch. 9 December: Invercargill. 14 December: Dunedin. 18 December: Timaru.