Much of the nutritional research on soybean [Glycine max (L.) Merrill] nodulation has been under greenhouse or laboratory conditions. Additional field data are needed on the influence of nutrients on nodulation and other plant characteristics. The purpose of this investigation was to determine under field conditions the effects of P and K fertilization on number and weight of soybean nodules; the chemical composition of leaves, nodules, and seed; the number of pods per plant; and seed yield. Annual P rates of 0, 15, 30, and 60 kg/ha were applied with 0 and 112 kg K/ha in one field experiment. In another, annual K rates of 0, 28, 56, and 112 kg/ha were applied with 0 and 60 kg P/ha. Either P or K applied alone increased the number of nodules per plant and per unit volume of soil. Applied K increased the number of nodules, total and individual weight of nodules, and the number of pods per plant more than P, but increases were largest when both P and K were applied. Applied K increased the K concentration of nodules, but had little influence on N, P, Ca, Cu, Fe, Mn, and Zn concentration, and decreased Mg; applied P without K increased the P concentration. There was a good correlation between the relative concentrations of P and K in leaves sampled for each of four different sampling dates and the concentration of these elements in the seed. Applied P in excess of 15 kg/ha did not increase soybean yields. Each additional increment of K up to the maximum used (112 kg/ha) resulted in seed yield increases when P was also applied, but with no added P seed yield responses to more than 28 kg K/ha were not significant. These results showed that application of both P and K individually increased nodulation and pod formation with more response from K than P. Maximum response was obtained when both elements were added. Even though the soil was very low in available P when the experiment was initiated there was no seed yield response to more than 15 kg P/ha. A good yield response was obtained from 28 kg K/ha and to increasing rates of K when 60 kg P/ha was added, thus indicating the higher requirement of soybeans for K than for P.

During a 3‐year period at three locations, the effects of populations and row spacings on 10 corn (Zea mays L.) hybrids (early, medium, and late maturing) were evaluated. Grain yields were increased as the width between rows decreased. Yields were usually higher with the late maturing variety planted at a medium or high population. Some exceptions to this generalization were observed. Percentage moisture in the grain at harvest was not affected by row spacings or plant populations but was affected by the hybrid used. Ear weight ‐increased with a decrease in row spacing and plant population and with increased time required for maturity. The ear‐to‐stover ratio was greatly affected by hybrids but was little influenced by row spacings and plant populations.

Selected treatments were chosen from three field experiments with corn (Zea mays L.) to determine effects of N rates on the vertical distribution of nitrates in the soil. The experiments were located on three different soil types and corn was grown for 5 consecutive years. Irrigation was a variable in two of the experiments.Appreciable amounts of NO3‐N accumulated in the soils when the optimum rate of 140 kg N/ha at Blacksburg and Charlotte Courthouse and 168 kg N/ha at Orange had been exceeded. Amounts of vertical distributions of NO3‐N accumulations were highly dependent on soil type, and on amounts of irrigation and rainfall. Lowest NO3‐N accumulations and highest NO3‐N losses were encountered in the Cecil fsl. An increase in NO3‐N was found in the Davidson clay loam whereas no loss or gain was observed in the Groseclose silt loam.Irrigation markedly reduced the maximum NO3‐N accumulation in the Davidson clay loam especially in the 120 to 195‐cm depth. Irrigation on the Cecil fine sandy loam had less influence on NO3‐N and hardly affected the spread of the accumulation zone. The data indicated that proper irrigation of soils with high internal drainage can markedly reduce NO3‐N loss through leaching; the reduction in NO3‐N loss in the Cecil fine sandy loam was from 48 to 5% at near optimum N rate of application.

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Three greenhouse experiments were conducted in 1969 and 1970 in which maize (Zea mays L.) inbred lines and single crosses were grown on an untreated acid Greendale silt loam (pH 3.9) and on the same soil adjusted with pulverized dolomitic limestone to various pH levels. Plant‐height measurements were made and dry‐weight yields were determined 27 to 38 days after planting. There were highly significant differences in growth among entries under highly acidic conditions. Inbred lines Connecticut 103 and Minnesota A632 grew very poorly in highly acid soil, while inbred lines Iowa B37 and Virginia 17 and two single crosses appeared to be tolerant to high acidity. There was a significant interaction between growth of entries and pH levels.