INVESTIGATIONS ON RICE GROWING IN BRITISH GUIANA. II. FIELD EXPERIMENTS TO TEST EFFECTS OF FERTILIZERS, LIME, AND CULTIVATIONS ON YIELD, COMPOSITION, AND NUTRIENT UPTAKE

Summary Factorial experiments were done to test the effects of N, P, and K fertilizers and lime on grain and straw yields. In addition, deep ploughing was compared with shallow, static with flowing irrigation, and in two Latin square experiments alternative P fertilizers were tested. Nitrogen fertilizers increased yields most on the most fertile soil type. Phosphorus fertilizers did not increase yields on the most fertile soil type, gave a moderate increase on the less fertile soils and prevented crop failure on soil containing much exchangeable Al. On the last soil type, water soluble phosphates were more effective than basic slag. Potassium fertilizers improved early growth at one site but did not increase straw and grain yields. Lime did not increase yields, even on the very acid soil containing much exchangeable Al. The weight of 100 whole grains was determined for rice from experiments sown with‘pure‐line’seed. Increased weight was normally found only when the field treatment increased yield. The N, P, K, and Ca contents of, and uptake by, straw and grain were determined for three sites with varying responses to applied N and P. Fertilizer N and K had little effect on the composition of straw or grain. Fertilizer P increased the P and decreased the N contents of straw and grain on P‐deficientsoils. Fertilizer P also decreased K content of the straw, increased that of the grain at one site, and also increased the Ca content of straw and grain. Lime increased the Ca content of the straw and of the grain at one site. Uptake of nutrients was affected more by yield than by composition.