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Oregon State University (1989)

Chilling and nutritional requirements of fruit trees in Yemen

Alkoshab, Othman

Titre : Chilling and nutritional requirements of fruit trees in Yemen

Auteur : Alkoshab, Othman

Université de soutenance : Oregon State University

Grade : Doctor of Philosophy (Ph. D.) in Horticulture 1989

A portion of this study was initiated to provide the basis for implementing a chill unit accumulation procedure in Yemen. Most continuous or daily minimum, maximum temperature models severely underestimated chilling units, and slight modifications offered little improvement for the complex models. Only the Crossa Raynaud formula approximated generally accepted chilling requirements for the peach and apple varieties tested. Of the average temperature models, the Weinberger Sharp model is best adapted to areas in Yemen where detailed meteorological data are unavailable. Another major goal of this study was to investigate the feasibility of using modern analytical equipment to make soil tests for arid regions cheaper, faster, and more efficient. Soil test experiments clearly indicate that a simple water DTPA extractant and Inductively Coupled Plasma (ICP) spectroscopy can provide efficient measurements of B, K, Ca, Mg, Na, S, Cu, Fe, Zn, Mn, P, Cl, SAR, PAR, and carbonates in a one-step procedure. The sorption isotherms of K, Ca, Mg, Na, P, S, Fe, Mn, Cu, Zn and B were determined. Data from all elements except Mn and Fe generally suggest that a plot of added vs. equilibrium solution concentrations is linear when agriculturally realistic rates are utilized. The linear regression constants for P and K sorption isotherms corresponded very well to the percent recovery in a multiple spiked solution. This suggests it is possible to evaluate soil buffering for P and K in a single two-step procedure. The final experiments were initiated to investigate the feasibility of utilizing tissue analysis to assist in prioritizing fertilizer needs for specific locations. The ratio based Diagnosis and Recommendation Integrated System (DRIS) diagnosis generally agreed with the sufficiency range method. DRIS was excellent in predicting relative nutrient responses.

Mots Clés : Fruit trees — Yemen — Climatic factors — Nutrition


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