Articles by Author: J B Jones
Search results for J B Jones
We found 129 results for you
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The Use of Roots to Test N, P and K Deficiencies in <em>Eucalyptus</em> Nutrition
Item type: Journal Article • Journal: South African Forestry JournalBioassays have been developed which can provide diagnostics of the nutritional status of trees. They measure the flux of N, P or Rb for K into roots from standard solutions where the rate of influx is inversely related to nutrient... -
Stimulation of Bud Production in <em>Eucalyptus globulus</em> by Paclobutrazol Application
Item type: Journal Article • Journal: South African Forestry JournalTrunk injection of paclobutrazol (Clipper) significantly increased the bud crop on 7-year-old Eucalyptus globulus (Labill.) seed orchard trees, within one year of application. This is the first reported stimulation of reproduction to occur, with eucalypts, in the season of application... -
Outline of a new approach to the study of competition
Item type: Journal Article • Journal: Proceedings of the Annual Congresses of the Grassland Society of Southern AfricaDifferential coefficients of five time‐dependent functions are proposed to quantify and define the following: the effect of competition on each of two competing populations, the relative aggressiveness of the populations, the competitive ability of each population with respect to the... -
A way to measure the spread of plants from a focus
Item type: Journal Article • Journal: Proceedings of the Annual Congresses of the Grassland Society of Southern AfricaThe relative frequency of occurrence of plants (or plant parts) is determined at increasing distances from a focus, where the relative frequency is unity. The area under the resulting frequency/distance curve is determined, as a measure of spread. Effect of... -
Production curves for pastures and veld
Item type: Journal Article • Journal: Proceedings of the Annual Congresses of the Grassland Society of Southern AfricaThe Gompertz curve applied to forage cumulative yields can be specified with three or more data points (yields at known times, including a possible zero yield at the start). Good correlations between pasture experimental data and the Gompertz curve, fitted... -
Effect of selective defoliation on species in mixed swards
Item type: Journal Article • Journal: Proceedings of the Annual Congresses of the Grassland Society of Southern AfricaSown pastures of Paspalum dilatatum (and other species) in Natal are subject to degradation by Eragrostis plana (mshiki) invasion. The ratio between these two grasses, growing together in small plots, was governed primarily by the relative heights, and secondarily by... -
A theoretical analysis of foraging efficiency of grazing animals
Item type: Journal Article • Journal: Proceedings of the Annual Congresses of the Grassland Society of Southern AfricaA mathematical model of the change in quantity of forage during grazing is constructed, assuming (1) that forage requirement by grazing animals is constant, and (2) that intake is equal to requirement when forage is in free supply but (3)... -
Notes on the value of <em>paspalum vaginatum</em> sw. As a pasture grass for saline and structureless soils
Item type: Journal Article • Journal: Proceedings of the Annual Congresses of the Grassland Society of Southern AfricaPaspalum vaginatum Sw. pastures were established on soils which had been denuded and physically degraded by over‐irrigation with an industrial effluent containing a high concentration of Na2SO4. The grass not only colonized the saline areas, but was able to tolerate... -
Simulation modelling in agriculture: General considerations
Item type: Journal Article • Journal: Proceedings of the Annual Congresses of the Grassland Society of Southern AfricaA computer simulation model is a detailed working hypothesis about a given system. The computer does all the necessary arithmetic when the hypothesis is invoked to predict the future behaviour of the simulated system under given conditions.