Adel M. Elprince

Multivariable fertilizer recommendation (MVFR) models allowed for variable rate fertilizer applications and precision agriculture. The objectives of this study were (i) to use binary logistic modeling to assess the importance of site variables in farms' decisions for implementing optimal N and K fertilization, and (ii) to combine multivariable logistic models in a geographic information system for the prediction of N and K fertilization class maps. These were based on experimental optimal N and K fertilization data at 67 sites and survey data for 22 site variables in an arid date palm ( Phoenix dactylifera L.) region (20,000 ha). Only nine of the 22 site variables were found to be statistically significant in influencing the probability of N and K responses: surface Fe, Mn, and Cu; profile residual NO ₃ –N; surface organic matter (OM), sand, and clay; surface extract soil salinity (EC _es ), and quantity of irrigation water ( Q _iw ). The probability of response ( Y = 1 means success and Y = 0 indicates failure) to the levels of minor, major, and excessive N application were expressed by the logistic models: logit[Pr( Y = 1|N = 0.25,0.5,1|X)] = 0.574 − 0.015 Q _iw + 0.768EC _es + 0.455Fe − 1.336 Cu, logit[Pr( Y = 1|N = 0.5,1|X)] = 3.274 − 0.011 Q _iw − 0.307Mn, and logit[Pr( Y = 1|N = 1| X )] = 4.394 + 1.463EC _es − 0.826NO ₃ –N, respectively. The corresponding models for K were: logit[Pr( Y = 1|K = 0.25,0.5,1|X)] = 4.424 − 0.104OM − 0.108NO ₃ –N, logit[Pr( Y = 1|K = 0.5,1|X)] = −1.189 + 0.015 Q _iw , and logit[Pr( Y = 1|K = 1|X)] = 37.582 − 0.560Mn − 0.036Sand − 0.046Clay. These logistic models were cross‐validated and combined in a geographic information system to derive N and K fertilization class maps using kriged‐interpolated data sets of the significant site variables. Logistic modeling could utilize low‐cost data for MVFR model calibration and validation and the production of soil fertilization maps with larger scales.

Peroxide application has been proposed as a method to control soil aeration. The objectives of this study were to formulate the rate law, identify the inorganic catalyst, identify preferred active centers, and hypothesize a mechanism for the H ₂ O ₂ decomposition reaction in Torrifluvents. The rate of decomposition of H ₂ O ₂ (aq) by Torrifluvents (10 locations in the Nile Delta) and synthetic Mn oxides was determined by measuring with a gas burette the volume of O ₂ (g) given off. Heat pretreatment showed that the catalytic activity of the air‐dried soil is essentially nonenzymatic on the time scale of the reaction. Pretreatment of the soil samples by NH ₂ OH–HCl (pH 2), designed for selectively dissolving MnO ₂ (s), completely deactivated their catalytic capacity. The pseudo‐first‐order rate coefficient, k *, for Torrifluvents was expressed by the equation: k * = k _o [MnO ₂ (s)](10 ^−pH/4 ), where k _o is a constant. Contrary to cryptomelane and pyrolusite, values of k * for birnessite satisfied the above equation, indicating that pedogenic birnessite was the active catalyst in Torrifluvents. Diethylenetriamine pentaacetic acid (DTPA) was found to be a more effective inhibitor than ethylenediamine tetraacetic acid (EDTA). A high value of the activation energy ( E ) was connected with a high value of the pre‐exponential factor ( A ) of the Arrhenius equation. It was suggested that the birnessite surface has two kinds of active centers: Mn ^III /Mn ^II and Mn ^IV /Mn ^III While the former is less numerous (ln A = 37 ± 4) with low activation energy ( E = 75 ± 4 kJ mol ⁻¹ ), the latter is numerous (ln A = 62 ± 3) and of high activation energy ( E = 144 ± 17 kJ mol ⁻¹ ). The Habes and Weiss mechanism explained the experimental results obtained.

Basic information is needed to estimate P status of Salicornia bigelovii Torr. with increased precision if progress is to be made in adapting this halophyte as a conventional oilseed crop for direct seawater irrigation in coastal areas of arid regions. The P nutrition of salicornia was studied by using the nutrient solution technique in the greenhouse. The culture solutions were seawater, enriched to 1/2‐strength modified Hoagland's solution [pH = 6.2 ± 0.2; electrical conductivity (EC) = 54 ± 2 dSm⁻¹], and P treatments ranging from 0 to adequate amounts of P for full growth. All stages of deficiency symptoms were observed at harvest, ranging from stunted growth, necroses, purplish coloration, chlorosis, and dark bluish‐green coloration to no symptoms. Dry and fresh weight of the tops were plotted against soluble P and total P values to give plant nutrient calibration curves that were fitted to the composite growth model by the least squares procedure. On the basis of the curve sharpness coefficient and range parameter output values and ease of sampling, semiwoody internodes, matured internodes and soluble P concentration were selected from the five plant parts sampled and the two forms of P determined as the best combination to diagnose the P status of Salicornia. About 480 mg kg⁻¹ of soluble P in semiwoody internode tissue was tentatively set as the critical concentration for growth of the salicornia. The corresponding value for total P was set at 780 mg kg⁻¹

Peroxides are used as O ₂ ‐generating agents. The decomposition of H ₂ O ₂ (aq) or MgO ₂ (s) in the presence of synthetic birnessite [δ‐MnO ₂ (s)] as a catalyst was observed by measuring the volume of O ₂ (g) given off. The experimental data fit a first‐order kinetic law and the mechanism proposed by Habes and Weiss can explain the experimental results obtained for the decomposition of H ₂ O ₂ (aq). The applicability of the proposed mechanism involving H ₂ O ₂ (aq) was based on the following: (i) the activation energy was relatively high (82 ± 3 kJ mol ⁻¹ ); (ii) the rate constant ( k ) was pH dependent, indicating that H ⁺ and OH ^‐ ions were formed in the process; (iii) a linear relationship (and not logarithmic) between k and the ionic strength indicated a reaction between an ion and a neutral molecule; and (iv) using birnessite with different fractional coverages of Co indicated that the reaction was heterogeneously catalyzed by Mn ^z+1 /Mn ^z active centers. Regarding MgO ₂ (s) decomposition, the experimental data obtained at pH 7.6 followed a rate law derived from a shrinking‐core model for fixed‐size particles. The rate of the reaction was controlled by diffusion through the Mg(OH) ₂ (s) product layer rather than by chemical reaction at the core surface. Compared with ionic peroxides, MgO ₂ (s) could be a potential O ₂ ‐generating agent for generating O ₂ (g) during a relatively long period of time.