Billy W. Hipp

Use of a solid‐state chloride electrode for chloride determinations in soil extracts

Abstract Studies were conducted to evaluate the use of a solid‐state chloride electrode for chloride determinations in soil extracts. The solid‐state chloride ‐electrode was used as an end point detector in the titration of chloride with AgN03 and direct reading of chloride in solution. The solid‐state electrode gave results very similar to those obtained with a silver electrode (r = 0.999) when used as an end point detector. Values obtained using the solid‐state electrode as a direct reading electrode were also well correlated (r = 0.998) but were slightly higher than results obtained by titration with a silver electrode.

A comparison of techniques for monitoring pH of growing medium

Abstract Studies were conducted to determine the reliability of four techniques for prolonged pH monitoring of small containers of media. Correlation coefficients of the methods tested (with saturated paste) were 0.96, 0.95 and 0.92 for porous cup solution extract, container effluent and placing the electrode directly in media, respectively. Continued coring for saturated paste determinations reduced fern growth by 38% during the period of study.

A preliminary comparison of the ammonium acetate‐edta soil phosphorus extraction method to the bray‐1 and olsen soil phosphorus extraction methods

Abstract The ammonium acetate (NH4OAc)‐EDTA soil phosphorus (P) extraction method was compared to either the Bray‐1 soil P extraction method for non‐calcareous soils or the Olsen soil P extraction method for calcareous soils to predict com and wheat plant tissue P concentration and grain yield responses. The NH4OAc‐EDTA method predicted yield and tissue P concentration responses to P fertilizer applications more accurately than the Olsen method at three of five sites. Both the Bray‐1 and NH4OAc‐EDTA methods were successful in predicting corn and wheat yield responses to P fertilizer applications in non‐ calcareous soils in many locations. However, a direct comparison of extracted soil P levels showed that the NH4OAc‐EDTA method extracted soil P at levels which were more closely related to the Bray‐1 method than the Olsen method.

Contribution of soil nitrogen mineralization rate to citrus production under subtropical conditions

Abstract Studies were conducted over a 5 year period on fine sandy loam soil to determine the importance of N mineralization rate on grapefruit (Citrus paradisi) production under subtropical conditions. Grapefruit trees grown on soils with mineralization rates greater than 0.47 ppm N/day produced near maximum yields during the first 3 years that young trees were in production but did not supply enough N after trees were large and fruit yields were above 16 MT/ha. Soil mineralizing 0.65 ppm N/day supplied enough N to produce 72% of the yield produced by trees fertilized with application of 148 kg N/ha.

Residual effects of clover on nitrogen nutrition of crops grown on blackland soils

Studies were conducted on two Blackland Prairie soils at Dallas, TX to determine the influence of clover plowed under on N nutrition of subsequent crops. Wheat yields were 103 and 86% of the yields obtained with 90 kg N/ha for the first and second crops after clover, respectively. Yields of nonfertilized wheat following fallow were 75 and 72% of the yield obtained with 90 kg N/ha for the first and second crops, respectively. Forage sorghum (non‐fertilized) grown as the first, second and third crop after clover produced 93, 80 and 43%, respectively, of the yields obtained with application of 90 kg N/ha. Nitrogen concentration in whole forage sorghum plants was 2.44 and 1.21% when grown as the first and third crop after clover, respectively. Nitrogen concentration in forage sorghum with N applied was 2.5%. These studies indicate that N from clover plowed under in Blackland soils may preclude N response by the first crop after clover. Some benefit may be obtained by the second crop but little if any...

Influence of N on growth and tissue N concentration in Leucophyllum candium (violet silverleaf, cenizo)

Abstract In greenhouse studies, M application up to 100 ppm increased growth of L. candi dum. Tissue nitrogen concentrations for optimum growth were > 1.5% for whole plants and > 2.3% for plant tips.