A laboratory study was conducted to determine the influence of redox potential and soil pH on the distribution of Fe, Mn, Zn, and Cu in Mhoon silty clay loam soil (Typic Fluvaquents) and to provide insight into factors affecting micronutrient dissolution and mobility in soil. Generally, greater amounts of Fe, Mn, Zn, and Cu were found in the Na acetate (exchangeable) and pyrophosphate (organic) extractions at low pH and Eh than at high pH or Eh. In contrast, the amounts (except Mn) in the water‐soluble, NH2OH·HCl, and oxalate fractions were greater at high pH or Eh. Although the micronutrients were brought into solution at low pH and Eh, much of the soluble cations soon associated with the exchangeable and organic fractions. After reduction, mobilized Fe associated about equally with the exchangeable, organic, and NH2OH·HCl fractions; mobilized Mn with the exchangeable and water‐soluble fractions; mobilized Zn with the organic fraction; and the mobilized Cu with the organic and water‐soluble fractions. Separation of the water‐soluble fraction into free ions and those complexed by soluble organic matter indicated that micronutrient cations were complexed by organic matter to a greater extent in reduced soil.

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Nicotiana tabarum L. cv. ‘Burley 21’ was grown in the field to determine the influence of rate of N fertilization on accumulation of dry matter and certain nitrogenous constituents during the growing season. Nitrogenous compounds in tobacco are presently of interest from a human health standpoint and the chemical constituents of tobacco leaves are known to be associated with dry matter accumulation. Accumulation of dry matter, protein N, and total N in plants treated with high rates of N fertilizer (up to 450 kg N/ha) was slower than in plants not fertilized or those fertilized with low rates of N during the early part of the growing season. The reduced rates of accumulation were particularly evident until near the flowering stage of growth (70 to 77 days). Thereafter, accumulation plants treated with high rates of N equalled or exceeded that in plants treated with low rates. Weight of dry matter and all measured constituents were greatest in high N treatments at harvest; however, N fertilizer delayed maturity 1 to 2 weeks. Exchangeable Mn in soil and concentration of Mn in leaves near 40 days increased as N fertilizer level increased. Values for Mn were lower than the literature would suggest as likely to produce toxicity in plants. Thus, factors in addition to Mn toxicity must be considered to explain the observed reduction of early growth by N fertilizers.

One greenhouse experiment and four field experiments were conducted during 1964–65 to determine (a) the effect of rate, time, and method of P fertilization on grain yield, yield components, and cooking quality estimation of rice, and (b) the existence of N × P interactions. Increasing P in 1964 increased lodging and reduced grain yields and 1,000 grain weight. In 1965 there was no influence of P rate. Preplant P produced darker green vegetation, broader leaves, and taller plants than did the midseason application. Differential responses disappeared by harvest time and no differences occurred except for cooking characteristics, which were more favorable with the preplant application. Cooking characteristics were not affected by P rate, but were less favorable as N was increased in three experiments and more favorable in the other experiment. Interactions between time of P application and N rate showed cooking characteristics were more favorable as N was increased and P applied at midseason than when P was applied preplant. Interactions between P application time and P rate showed that increasing P and applying it preplant improved cooking characteristics over those of the same rates applied a midseason. The N X P interactions were inconsistent. In the greenhouse study, soil‐incorporated P increased straw weight more than did broadcast P, but did not affect plant height, panicle number, or panicle weight. Increasing N increased panicle number, total panicle weight, straw weight and plant height. Increasing P decreased height and increased values for the other variables. The only interaction showed that increasing P and incorporating it increased panicle number and straw weight more than broadcasting it.