A sand-culture experiment with lettuces is described, having as its principal purpose the study of the relationship between the potential responses of plants to applications of nitrogen, phosphorus, and potassium fertilizers and the composition of. their foliage. Plants were supplied initially with five levels of these nutrients in all combinations, samples of plant material were taken fot analysis at various stages of development, and at 44 days from sowing additional quantities of nutrients were supplied to some of the cultures in order that their response potentialities might be determined. The present paper analyses the effects of the nutrient interactions on plant dry weight, further results being left to subsequent papers.

Lettuce plants grown in sand culture, and receiving nitrogen, phosphorus, and potassium at five levels in all combinations, were analysed at different stages of growth for total, soluble, and nitrate nitrogen. An attempt was made to relate these analytical data to the subsequent response (in dry matter production) shown by the plants when a further amount of nitrogen was supplied.

In a sand� culture experiment with lettuces, the water content (as per cent. of dry matter) of the aerial portions was studied in plants subjected to five levels of nitrogen, phosphorus, and potassium supply in all combinations.