Brown-heart in Swedes.

New Zealand Journal of Agriculture, Volume 57, Issue 6, 20 December 1938, Page 511

Brown-heart in Swedes.

Trials with Application of Borax.

C. S. Dalgliesh,

Fields Instructor, Rotorua.

IN common with quite a number of districts throughout New Zealand, brown-heart has been prevalent for a number of years in swede crops of the South Auckland Land District. Unfortunately, as far as is known, there is no means of detecting superficially the presence of brown-heart in the average swede crop, as, in general, the crop appears normal and healthy, and only when bulbs are cut is brownheart detected. Instances occur in which swedes are rough in the skin and irregularin shape and show an extensive degree of the disease when examined by cutting, but it is only occasionally that one meets with such conditions and is able to state from observation only that brown-heart is prevalent.. Signs of Disease. A bulb affected with brown-heart shows a clearly defined; zone mottled with brownish areas, and not arranged to any definite pattern (Fig. 2). In the case of slight attack the area involved may be merely a small patch or arc of tissue. In very severe cases small' cracks occur, marking the outer limits of the diseased zone. (Fig. 1). The trouble in swedes only slightly affected is often confused with frost injury, and it is not easy to recognize slightly infected bulbs after they have been exposed to a severe frost. In general; however, it may be said that brown-heart mottling can be recognized by its presence in a ring around the. centre of the bulb and its absence in the marginal zone. Frost, on the other hand, always affects the outside, first.. That there is no connection between the two types of injury is clearly shown on cutting swedes before frosts have set in, when the trouble may be found to be fairly extensive. ' Feeding Value Reduced. Although there is no actual loss in bulk, the feeding-value of a brown-heart-

affected crop is markedly decreased. An analysis carried out in Scotland showed an , increase of approximately. 2 per cent, in the fibre content of the diseased swedes, accompanied by a decrease of from 3 per cent, to 4 cent, in the soluble, carbohydrates. The amount of sugar in the juice may be reduced by as much as 12 per cent. These changes, taken altogether, result in a serious reduction in the feeding-value. If affected swedes are boiled for • human consumption they remain hard, stringy, and. tasteless. It was thought that the cause of brownheart was due to acidity of the soil. In experimental trials conducted in New Zealand in which special attention was given to thorough cultivation, liming, and manurial treatment no definite improvement was obtained. Where farm-: yard manure was used, and on situations where haystacks had been built, swedes were invariably found to be more or less free from brown-heart. Great Britain and New Zealand investigational results concur in this respect. Hurst, Dominion Botanist, Canada, showed by pot test trials that it took about 30 tons of wellrotted farmyard manure per'' acre to eliminate the disease completely. Effects of Liming. The effects of a free use of lime proved disappointing in New Zealand, as such did not overcome the trouble. ; Similarly, in the west of Scotland it was a common experience in farming practice to find that a heavily limed field yielded a high, percentage of brown - heart - infected swedes. Scientific-research workers in

Great Britain and Canada formed the opinion, after much detailed research, that the - disease was due to a deficiency of the element-boron- “ Boron never occurs free as an element, but in combination usually as boracic ■ (boric) acid and in several minerals, such as crude borax.” This led to experimental trials being conducted by broadcasting borax at the rate of 20 lb. per acre on the land prior to the sowing of swedes. Results were a good all-round improvement, with complete control in several trials. In the 1935-36 season the Department of Agriculture carried out several trials throughout New Zealand with applications of borax on swede crops to gain information .of its use as a means of control of brown-heart on New Zealand soils. • . The treatment consisted of mixing 10 lb. per acre of borax with ■ sufficient fertilizer to sow an acre, the treated' area being compared with the farmer’s crop alongside in which the same manurial treatment was given but no borax added. In the majority of the trials satisfactory control of the disease was obtained by the use of borax, but in some trials detrimental effects in germination was noted. For detailed particulars, see the Journal of Agriculture, Vol. 53, August, 1936, page 99.

Mixing with the Fertilizer. In the sowing of turnips and swedes in the North Island most farmers adopt the method of mixing the seed with the fertilizer. Experience now gained in the use of borax clearly shows that when the seed comes in close contact with borax, as is the case when seed, fertilizer, and borax are all mixed together, detrimental effects to germination is very likely to occur. Two trials were conducted in the Rotorua district in the 1935-36 season. Germination and control of brown-heart was very satisfactory in both crops where borax was used, and in the main crops on both farms where the trials were carried out brown-heart was much in evidence. This led to a. free use of borax in the 936-3 season by farmers of the district. A number of farmers purchased borated fertilizers manufactured by proprietary firms ; others purchased borax and mixed it with the fertilizer, using it at the rate of 2J lb. to 31b. per 100 lb. of fertilizer. Germination suffered severely .• in many crops, but control of brown-heart was entirely satisfactory. In this same season the Department of Agriculture conducted further trials with borax at rates of 3 lb., 6 lb., 9 lb., and 12 lb. per acre, the respective quantities being mixed with 3 cwt. of basic superphosphate per acre and seed. Further Trials. In addition, trials with applications of borax at 10 lb. per acre broadcast on the land prior to sowing, and also in topdressing the crop, were carried out. Five trials were conducted in the RotoruaPutaruru district, and in four the mixing of seed, fertilizer, and borax proved extensively detrimental to germination. Borax applied even as low as 3 lb. per acre did much damage when mixed with fertilizer and seed. The method of applying borax by broadcasting on the land prior to sowing did not .result in any harmful results to germination. All applications of borax— 3 lb., 6 lb., gib., and 12 lb. per acre mixed with

fertilizer and seed, . and applications by broadcasting and top-dressing — very satisfactory results in the control of brown-heart. This was particularly outstanding in a crop in the Reporoa district, where the incidence of ' brown-heart on areas not treated with borax was’ very pronounced. ' During the 1937-38 season trials were, confined to borax broadcast on the land previous to the sowing of the swede crop at rates of 10 lb., 15 lb., 20 lb., and 30 lb. per acre. No detrimental effects to seed germination occurred, and complete success in the control of brown-heart was secured. In most crops the swedes were more healthy in appearancefresher tops

and cleaner in the skin—on boraxtreated areas than on untreated plots, as shown in the illustrations. Liming not Recommended. Applications of borax broadcast on the land at the rate of 15 lb. per acre prior to sowing gave an average increased weight of 51 tons per acre over areas not treated. As lime applications appear to be incompatible with brown-heart control, liming immediately before sowing a swede crop is not, recommended in districts where brown-heart is prevalent; nor should fertilizer mixtures including borax and containing free lime be used. The method of applying borax alone by broadcasting is not practical for the farmer, but the trials conducted in the Rotorua-Putaruru area clearly showed that 10 lb. per acre of borax gave satisfactory results, and that up to 30 lb. per acre applied by broadcasting did not produce harmful effects to seed germination. It is therefore evident that the safe method is to apply borax before sowing and not to allow close contact with the seed. The mixing of borax at the rate of 8 lb. per acre with 2 cwt. of fertilizer and the application of this to the land a few days before sowing, the seed being sown with 1 cwt. or more of fertilizer, is a reasonable measure to adopt, and has been adopted as a farming practice in this district with successful results. ■> « «

| Trials conducted by the I Department of Agriculture i show that the application of ? borax affords a large measure of control of brown-heart in i swedes. It is emphasized, | however, that the safe j method is to broadcast the i borax before sowing, and I not to allow it to come into j close contact with the seed. I