Book Reviews

Four publications on hemp growing

An integrated assessment of hemp (Cannabis sativa L.) and flax (Linum usitatissimum L.) as sources of fibre for newsprint production. Shaun Lisson 1998. Doctoral thesis, Dept. of Agricultural Science, University of Tasmania, Hobart, Tasmania, Australia. 211 pages.

Feasibility of Industrial Hemp Production in the United States Pacific Northwest. Daryl T Ehrensing 1988. Agricultural Experiment Station - Oregon State University, Corvallis, Oregon, USA. Station Bulletin 681. 37 pages.
Available online at:

The cultivation of hemp. Botany, varieties, cultivation and harvesting. Ivan Bócsa and Michael Karus 1998. Hemptech, Sebastopol, CA, USA. 184 pages.

The 5 minute guide to industrial hemp in New Zealand. D.J. McIntosh, Richard Barge and Thomas Brown 1998. New Zealand Hemp Industries Association Inc., Auckland, New Zealand. 63 pages.

        Four publications on hemp have recently appeared, covering largely the same topics: What is hemp?, How should it be grown?, What yields can be achieved?, and ultimately, What about the economic value of the crop for farmers? These publications, however, were written by authors from very different back-grounds, which makes a comparison of these works all the more interesting.
        Shaun Lisson's thesis reports results of experimental research and tries to make an assessment of the economic viability of hemp in Tasmania. A summary of the contents of his thesis can be found on page 41 of this issue and the chapters of the thesis on irrigation is published as a paper on pages 9-15 of this issue. Although Daryl Ehrensing's Agricultural Experiment Station Bulletin 681 comes from quite a different part of the world, and is based on desk research rather than field experiments, it has a lot in common with Shaun's thesis. Both authors are agronomists trying to make a non-partisan assessment of hemp. They both conclude that in their part of the world hemp will require supplemental irrigation to reliably maximize productivity. With respect to economic viability for Tasmania Shaun Lisson concludes,
        "The minimum bark price (mill gate) that is likely to attract farmers would vary between flax and hemp and between growing conditions. Irrigated hemp and flax crops grown in the more productive north-west area of the state would require a price in excess of about Australian $650/t. These minimum bark prices are not attractive to the newsprint industry at present. Future viability will depend on a number of factors, including: fibre yield and quality (eg. bark proportion in the stem and fibre tensile strength properties) improvements, elevated kraft pulp prices, and the establishment of strong markets for the stem core fraction and the seed of flax."
        This is in full agreement with the conclusion Daryl Ehrensing draws for the the Pacific Northwest of the USA,
        "Hemp production in western Europe is made economically feasible primarily by direct subsidies by the European Community. Since government subsidy is extremely unlikely in the United States, a thorough understanding of hemp production practices and costs is essential to determine the viability of production. Total biomass yields will need to be substantially greater than those previously recorded in other countries for hemp to be economically feasible in the Pacific Northwest at current prices for raw hemp fiber and seed."
        Interestingly, Ehrensing also concludes that,
        "Pacific Northwest growers may remain at an economic disadvantage compared to Midwest growers who have lower costs and can produce hemp using available summer rainfall rather than irrigation."
        The book by Ivan Bócsa and Michael Karus originally was published in German and was reviewed in the June 1997 issue of this journal. The authors of this book are scientists, but both can be classified as hemp partisans. For some reason, it is apparently hard to engage in hemp research for a long period and to continue considering it as "just another crop". Well, while we're at it, let's see what Bócsa and Karus say about the economic viability of hemp (page 144),
        "By and large, only EU subsidies make hemp cultivation a profitable venture under current economic conditions. Assuming a dry stalk yield of 9 metric tons per hectare (4 short tons per acre) or a dual usage fibre yield of 6 metric tons per hectare (2.7 short tons per acre), a minimum subsidy of DM 800-1,200 per hectare (US $ 190-280 per acre) would be required."
        Like Lisson and Ehrensing, these authors point out that,
        "Higher crop yields from optimized varieties combined with lower harvesting costs due to new harvesting machinery will contribute to the future feasibility of hemp cultivation."
        The fourth publication "The 5 minute guide" presents a much more optimistic point of view than the previous three studies and states (page 55) that,
        "Hemp can provide three times the curent rate of return of other traditional land uses with a forecast gross margin of between $1,000 and $10,000 per hectare."
        I hope that the authors of this guide spent more than 5 minutes considering the question of the gross margin of hemp relative to that of other crops, but they might want to spend still some more time on this matter. A visit to nearby Tasmania seems a good idea.
        Obviously, there is more to be said about these four publications. Shaun Lisson's thesis is a thorough piece of work, no doubt it will yield several scientific publications. One thing particularly worth mentioning is the hemp simulation model he developed. I hope this model will be made available to those interested, as it might allow one to use a computer to explore the potential of hemp for different pedoclimatic conditions and thus the model will be complementary to field testing. Daryl Ehrensing's report supplies, apart from its assessment of the economic feasability of hemp, a thorough review of the agronomic literature. Instead of merely repeating assertions found in other recent sources he clearly did an original job and came up with some quite old references that I have not seen cited before. His report further has the enormous merit of being easily accesible via the web. The book by Bócsa and Karus has been reviewed in this journal when the original version in German came out. The English version is even slightly better than the original: some minor mistakes have been corrected, the cover of the book is nicer and a photo showing the authors side by side has been included. Last but not least, The 5 minute guide's authors seem to get carried away a bit too easily by their hemp enthusiasm. However, they did produce a very nice looking booklet, which hopefully will contribute to starting a New Zealand hemp research programme.

Hayo van der Werf