The Effect of Fertilizers, Manures, Irrigation and Ridging on the Yield of Pyrethrum.

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Kroll, U.
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The results of experiments with fertilizers, irrigation and ridge planting on pyrethrum are discussed. Phosphorus appears to be in short supply on many soils in the Kenya Highlands as well as in Southern Tanganyika. Applications of 150 to 200 lb. T'I'iple Superphosphate at planting time either placed into the planting holes or below the ridges are recommended. The effect of these treatments usually lasts over two to three seasons. Basic phosphates have shown no advantage .over superphosphates. Nitrogen and potash have so far produced no yield increases. Calcium (lime) has on occasions and on highly leached acid soils given positive responses. Results are not conclusive. Applications of the minor elements Zinc, Molybdenum and Copper have had no results. Farmyard manure, except in nurseries to stimulate the initial growth of seedlings, is not recommended. Mulch between the rows of plants has produced yield increases especially in drier seasons and at the warmer altitudes. Green manures have, on the whole, been disappointing. One year of a green crop between two pyrethrum plantings, does not constitute a means to keep up yields. A grass ley should be included in a balanced rotation. Satisfactory yields on land which is repeatedly planted with pyrethrum can only be maintained by phosphorus application, even if a reasonable rotation is followed. The pyrethrum content cannot be influenced by any fertilizer or manure. Irrigation at the rate of 4 ins. per month can increase the flower yield as well as the pyrethrins content during dry spells within the growing season but does not prolong flowering into the dry season. Ridge planting has in most cases given increased yields and is recommended.
East African Agricultural and Forestry Journal, 28, pp. 139-145