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The manipulation of irrigation and drying-off schedules of sugar cane to increase sucrose yields T. Mushipe, C. Chiduza and B. V EDITORIALThe seven articles in this issue Volume 4 ( 2 ) ,consist of three research papers from physics, two research papers from the agricultural sciences, one inaugural lecture and one book review. The current issue has a very good balance of the physical and biological sciences. This is important and in line with the policy of JASSA, that is, the publication of papers on applied sciences. Previously there has been a preponderance of papers from the agricultural sciences. In this issue, the three submissions from the discipline of physics has, for the moment ended that tradition. This is a welcome development as this widens our latitude of papers on applied sciences. The two agro-based papers present particularly interesting findings because of their relevance to the Southern African regional context, in as far as the economic importance of sugar production, both for export and local consumption, and the significance of semi-arid agriculture in the region.The paper on sugar cane establishes that induction of mild stress, in the form of restriction of water to levels that do not fall below crop factor 0.85, increases sucrose yield. The second agricultural based paper establishes poor crop establishment as a major factor affecting crop production in the semi-arid areas of Zimbabwe. Agriculturalists in semi-arid areas will find this paper interesting. 'A pedestrian route to Gleason's theorem' is the creative title of one of the physics papers. The author here offers what he calls an elementary proof of the 'theorem' and one which is different from those previously offered and it is interesting.The inaugural lecture is this issue-. 'New Directions for Pesticide Use' is the first in this series. This lecture is an intellectual plea for the serious consideration of'the middle road' approach to Integrated Pest Management from a prominent crop scientist. It is argued that the misconception that pests can be eradicated rather controlled has subsequently led to the pesticide treadmill and that the proper use of pesticides should involve a thorough understanding of pest population dynamics and how this is influenced by the pesticidal control ami the inlestation/yield loss relationship and the economics of pesticide use. The Integrate Pest Management approach is argued for, convincingly.Finally the review of the book Lecture Note* on Pharmacodynamics represents almost exclusively the first review ever in the JASSA of an article from the medical -ciences. This is a welcome development, even more so for the fact that this is a text book for students of the medical sciences. C. F. B. Nhachi Editor-in-Chief IV Journal of Applied Science in Southern Africa

This chapter considers specific information on the status and depletion of nutrients in Vertisols, responses to fertilizer nutrient input, and the impact of improved technologies on nutrient requirements. Particular emphasis is directed to Zimbabwe and Ghana, which have two contrasting moisture regimes, with a view to better understanding nutrient-moisture interactions for the development and implementation of sustainable nutrient management practices.

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Different management techniques and methods of physical and chemical characterizations of Vertisols in Zambia are discussed. In addition, the major limitations to crop production are also discussed.