An evaluation was made of the changes in soil reaction and exchangeable base content of two Red‐Yellow Podzolic soils and one alluvial soil resulting from high rates of application of ammonium nitrate and of ammonium sulfate. Severe reductions in exchangeable base level and lowering of soil pH occurred within a year after beginning N applications. The undesirable effects occurred deep in the soil profile where corrections would be difficult, if not impossible, from a practical standpoint. Exchangeable K was lost from the soil faster than other bases at the higher rates of N. No indication of a subsoil zone of accumulation of bases leached out of upper horizons was observed. The measured losses of exchangeable bases were appreciably lower than calculated CaCO3 equivalents of the residual acidity of the fertilizer except for the higher N rates on the Toa clay loam.

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Grass tetany, a metabolic disorder of cattle on pasture, has often been related to low Mg and high K levels, and high K/(Ca+Mg) equivalent ratios in forages. These forage mineral imbalances often occur during wet periods when soil O2 may be low. The effect of 2, 4, 8, 16, and 21% soil air O2, on Ca, Mg, and K contents of rye (Secale cereale L.), ryegrass (Lolium multiflorum Lam.), and arrowleaf clover (Trifolium vesiculosum Savi) was studied in the growth chamber at 22 C day air temperatures and 12 or 16 C night temperatures. Increasing soil O2, had little effect on Ca or Mg content of rye forage but increased K from 2 to 5%, and increased the K/(Ca+Mg) ratio to over 4. Uptake of K, Ca, and Mg was generally lower at 12 than at 16 C. Ryegrass forage, grown at increasing soil air O2, had higher K, Ca, and Mg contents. Concentrations of K, Ca, and Mg in ryegrass were lower at 12 than at 16 C. Magnesium levels at 2 to 16% soil O2 were below the critical level of 0.2% at 12 C air temperature. Soil O2 had little effect on the composition of arrowleaf clover forage, except for a small increase in K. These results indicated that ryegrass forages, grown on poorly‐drained soil would likely be more tetany‐prone than that grown on well‐drained soil. However, rye forage would be more tetany‐prone when grown on well‐drained soil. The high Mg levels of arrowleaf clover showed its value in balancing tetany‐prone grass forage when it is maintained in a pasture.

Photosynthetically active radiation (PAR) was measured at two times of day (8:00 am and noon Central Standard Time) in a 915 × 915-cm area of a 1006 × 915-cm gable roof greenhouse. PAR measurements were taken across a grid at 40-cm intervals, a total of 529 data points. Spatial variation of PAR in the greenhouse was evaluated through contour plots and the geostatistical technique of semivariogram construction. Semivariograms provide a visual guide to the degree of spatial correlation of a variable, allowing a quantification of the distance at which variables cease to be spatially correlated (the range) Measured PAR contained distinct zones of lowered values, a function of overhead greenhouse structures, wall-hung electrical boxes, and tall plants in adjacent greenhouses. Although the amount of PAR changed over time, zones of high and low PAR remained relatively constant, except at the sides of the greenhouse. Constructed semivariograms revealed that PAR contained strong spatial correlation (up to a 350-cm separation) as measured in the north-south direction, moving parallel to greenhouse bench placement. When PAR measurements perpendicular to benches (east-west) were used in directional semivariograms PAR was found to be completely random, plotting as a horizontal line called a nugget effect. Thus, plants placed perpendicular to the greenhouse benches (east-west) would not be affected by the spatial correlation of PAR.