SOIL AND HEALTH

New Zealand Listener, Volume 17, Issue 418, 27 June 1947, Page 9

SOIL AND HEALTH

Plant Biologist’s Opinions

HE following comment on the paper presented to the recent Science Conress in Wellington by Sir Stanton Hicks was written for "The Listener’ by DR. I. D. BLAIR, of Canterbury Agricultural College, but was not available in time for inclusion with the text of Sir Stanton’s address in our last issue. IR STANTON HICKS is a scientist and develops his argument concerning _ soil, food, and health from his own experimental data and critical observations within his own experience, His philosophy therefore is more

arresting than the usual vociferations and dogma of certain elements in compost circles, I think he is performing a service, if he makes people think, and inyestigators work, towards a clarification of our health balance-sheet, as shown betwéen what a primary produce exporting country like ours takes from the soil, in relatiot’ to what is added or returned thereto. It seems definite that although our control and prevention of microbial diseases has advanced, functional disorders and nutritional complaints in humans (and in plants) are claiming increasing toll and in fact are the reigning primary causes of death. It has at least to be proved that nutritively depleted soil is not the root cause of predisposing factor of this state. No doubt Sir Stanton’s viewpoint will be scorned

in some orthodox circles but the ‘iin tion which I think he raises remains: Is | ‘the productive capacity of New Zealand : soil, as measured in terms of exported | meat carcases and by-products, of the : same order in terms of health in our people, who at least hope to live longer than fat lambs and porkers and whose vigour is not a matter of body weight, proportion, of lean or fat or hair production? : Observations in Canterbury I am interested in certain features of Sir Stanton’s remarks concerning organic matter in the soil for the reason that in some of our plant disease studies there appear to be allied tendencies. Thus some diseases in Canterbury wheat have under experimental conditions been notably checked by incorporating in soil before wheat sowing, heavy quantities of undecomposed straw-not merely ploughed in stubble. Likewise in Canterbury, potato blight causes much less tuber decay where the crop is grown after ploughing in heavy preceding crops of lupins as green manure. When in Texas, I was impressed by the evidence of prevention of devastating cotton root rot through ploughing in undecomposed organic matter before cotton planting. The point is that in plant health also, we have the evidence that organic supplements (not compost in my examples) enhance disease avoidance. It must be said though that the effect is not directly one of soil nutrition in relation to disease. For those who are interested, the technical explanation in these instances, of the manner in which some forms of organic matter may limit plant disease activity is as follows; Straw, lupins, etc. are cellulose-rich materials and as such when added to soil they stimulate a tremendous microbe increase, This micro-population is effective then in decomposing added supplements. In this process the normal soil inhabitants by chemical and physical effects limit or suppress development of some plant disease organisms which through their parasitic habit are less well adapted to take part in the obligatory decomposition activities, They are suppressed and die out at least temporarily; | for a sufficient interval to permit healtay growth in the subsequent disease-sus-ceptible crop. If these latter observations appear pointless apropos to the diract subject, may I try and wriggle out of the situation by emphasising that studies on organic matter in anima] health have been preceded by several years of like investigations concerned with problems in man’s food crops,