NUTRITIONAL TRIALS IN GREENHOUSE BEDS AND BORDERS
Before discussing various aspects of nutritional trials in greenhouse borders, reference should be made to alternative approaches to plant nutrition. If the only object is to study the response to plant nutrients, sand or water culture would be the obvious choice; precise nutrient concentrations may be established in this way without the complications arising from adsorption or fixation in the soil. Again, if we require fully defined environmental conditions then controlled environment chambers would seem far preferable to the somewhat variable conditions of the greenhouse. Both these facilities are admirably suitable for basic nutritional studies, and we have used sand culture extensively for some of our work. If, however, our aim is to establish or improve nutritional programmes for practical application in commercial horticulture, then large-scale experiments in greenhouse beds and borders are essential. Thus the application of data obtained in sand culture is complicated by the problem of relating nutrient concentration in solution to soil nutrient status. The use of growth chambers would generally prevent the inclusion of large numbers of treatment combinations. Furthermore, even when soil is used as the growing medium in pots or small containers, the rooting conditions and nutrient distribution are hardly comparable with those of a greenhouse border.