With Three Text-figures)The materials and methods have been described in the first paper of this series (Glover, 1953). All experiments were of 3 3 factorial design (Yates, 1937) involving three different levels of supply of nitrogen, phosphorus and potassium.

With Two Text-figures)As part of the overall programme of research directed towards an understanding of fertilizer needs of crop plants in East Africa a study of the nutrition of maize in sand culture has been made.The purpose of the work was to study growth and yield in relation to changes in the proportion and concentration of the major nutrients, nitrogen, phosphorus and potassium, and if possible to relate the results to the field behaviour of the crop in fertilizer trials conducted by another section of this organization. Simultaneously studies of the uptake of nitrogen and phosphorus were also undertaken. These latter are discussed in the second paper of this series.This first paper deals only with growth, yield and nutrient content in relation to the nitrogenphosphorus balance, though the methods now to be described were common to all experiments. MATERIAL AND METHODSThe experiments were conducted in a pot-culture house with a glass roof and no sides except for a retaining wall some 3£ ft. high, so that air circulated freely through the building.The containers were hardwood boxes whose walls were 1 in. thick. They were supported on legs which permitted the collection of the displaced nutrient solution from a drainage hole in the bottom. They were sealed with beeswax, which was first ironed into the wood with a hot iron, then a thick layer of beeswax was applied to the walls and floor. Tests showed that this coating did not deteriorate over long periods, and that nitrogen, phosphorus or potassium did not accumulate in it or pass through into the wood of the walls.Different sizes of boxes were used depending on whether the experiments were designed to run only for a few weeks or right through to maturity. The boxes used in the 'uptake' experiments were 18 x 12 x 12 in., and each contained two plants.An acid-washed quartz sand was used in all experiments, and its particle size was such that it held sufficient water to provide adequate supplies for transpiration between renewals of the nutrient solutions.The nutrient solutions were applied every alternate day, and their volume was such as to saturate the sand and completely displace the previous application. This complete displacement was essential for the measurement of uptake of the nutrients from the solutions.A series of preliminary experiments showed an unexplainable, high, apparent consumption of phosphorus. This was found to be due to the fixation of phosphorus by traces of iron in the sand which were difficult to remove even with repeated acid washings. An attempt was made to saturate the fixing capacity of the iron by continuous exposure of the washed sand to a solution containing phosphorus for several weeks. Although apparent saturation was attained, as shown by the nonremoval of phosphorus from fresh solutions which were allowed to percolate through the bulk sand, fixation continued when the bulk sand was distributed to the containers in preparation for the experiments. As a result blanks were run throughout the experiments to determine the amount ...

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