THE CHALLENGE IN writing about agriculture for general readers lies in reducing the subject`s complexity. Farm work is surrounded by complex bureaucracies devised in the public interest to maintain food supplies and to provide raw materials for the country`s sizeable processing and transportation industries. In fiscal 1987-1988 the Canadian government spent $5.3 billion supporting the country`s two hundred thousand or so farmers. With the current drive to reduce government expenditures, pressure rises to trim their farm subsidies; we have begun counting the costs. Barry Wilson`s Farming the System traces Canadian farm policy for the past 30 years. Now the only full-time farm reporter on Parliament Hill, Wilson is uniquely placed to write this book. And he has produced a useful reference work. Brewster Kneen`s Trading Up looks specifically at those parts of Canadian agriculture touching the influential, commodity-trading organization Cargill Inc. of Minnesota. It is Kneen`s second book in two years on farm policy. But Trading Up is less satisfying than his earlier From Land to Mouth, a book-length essay based on Kneen`s farming experiences in New Brunswick. The author has lost something in the move from essayist to investigative journalist. Neither Wilson nor Kneen brings much in the way of farm-level observation to their work. Both books are dominated by argument and statistics, largely unrelieved by anecdote, description, or character. But they suffer from quite opposite journalistic problems. Kneen, described by his publishers as an economist and theologian, approaches Cargill with such obvious personal distaste for the company`s corporate sytle that it undermines his credibility. Wilson, on the other hand, presents his observations with excessive even-handedness, and Farming the System lacks the sort of order that comes from a consistent viewpoint forcefully argued. It is the product of that modern evil, "objective journalism." And, unfortunately, it winds up reading like another of the many government reports that Wilson spends so much of his professional life digesting for readers of the Saskatchewanbased farm paper, the Western Producer. Wilson`s book does contain a large body of original work, including interviews with policy makers seldom quoted outside the farm papers. It reveals how much stress there is on farmers and government in the late 20th century. And there is a particularly timely chapter on Quebec farm policy as an expression of cultural nationalism. But the book is pure policy. There is no attempt to outline historic changes in thinking among farmers themselves about cultivation and soil conservation or the intriguing crop alternatives now emerging on farms through biotechnology, organic, and plow-less agriculture. Wilson`s best chapters present interviews with insiders about top-level government policy making, particularly during the final years of the Trudeau government. There are interesting observations about the early-`80s cabinet battles of the former agriculture minister Eugene Whelan when farmers were out for his hide because of devastatingly high interest rates. And an interview with the economist Beryl Plumptre, who headed Trudeau`s Food Prices Review Board, is the basis of one of the book`s best chapters, which concerns the relatively minor influence of consumers` interests on national food policy. Kneen`s book seems too easy and offhand to land ,my journalistic blows on corporate Cargill. A private, family- controlled company, Cargill is the world`s largest grain-trading concern, with more than 44,000 employees in 55 countries and a Minneapolis head office that resembles a French chateau. Cargill exerts undue influence over government policy, both here and in the United States, Kneen argues. And he has traced an executive-sharing pattern between Cargill and government grain agencies that is indeed worrisome. However, Kneen relies heavily for factual material on other researchers, most notably writers at Forbes and Business Week, U.S. business magazines. Trading Up adds little to an understanding of Cargill beyond what has previously been written. Canadian agriculture shares the problems of agriculture everywhere. It has not adapted easily to the 20th century`s primary economic trends: industrialization and urban growth. There are fewer farmers producing greater volumes of food for an ever-increasing world population. The food industry`s processing, handling, and transport sectors have fallen into fewer corporate hands. Kneen claims corporate concentration has stage-managed the changes. But there is more to it than that. Farm abandonment is really the story of civilization. Corporate concentration is the way of the world. And complete understanding of the phenomenon will depend on a more rigorous study than what`s offered in Trading Up