الفهرس 
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Abstract
This study was carried out in department soils, College of Agriculture, Minia University, to study the status of K in soils of the great groups distinguished in Minia Governorate. Forms of K in surface layer of the studied soils were measured and correlated to some soil properties. The effects of planting and K fertilization on the forms of K these soils were examined. The parameters of the Q/I relation of K in each soil great group were estimated and correlated with some soil properties, soil K forms as well as the available potassium in each great group.
The parameter(s) of the Q/I relation that suitably described the status of K in these soils were presented and estimated the required level of K fertilizer.
The study including:
1- Measurements including different forms of existence of K in soils of the great groups and its relationship with some measurements such as total K, soluble K, exchangeable K, reserve K, stepK, step-K +Kn,and Kn +K1 : The K-saturation values, and the fixing ability of potassium by these samples were also determined.
2- Studying the parameters defining Q/I intensity and capacity factors that govern the level of availability under each great group of Minia Governorate. Most of these parameters were obtained through the Woodruff’s ratio law, Beckett’s O/I measurements, and ion exchangeGapon coefficient. The O/I parameters included the ARK , -∆Koand PBCK values. The Gapon selectivity coefficient was (K) calculated from exchangeable K, Ca and Mg, together with the potassium adsorption ratio in the saturated soil paste extract. Modified Gapon coefficient (K’’) was also calculated from the ion exchange equations by taking (-∆Ko instead of K exchangeable and ARK).
3- Studying the effect of incubation and K addition soils great groups of Minia governorate on the available and fixed forms of K as well as on Q/I parameters.
4-Two biological experiments were conducted in two different growth seasons on wheat and zea (maize) for measuring the effect of cropping and K fertilization using three treatments (45, 90, and 135 Kg K /fed plus the control) in three plant ages(20, 40, and 60days) on K forms and Q/I parameters. The ability of using the Q/I parameters in describing potassium status, potassium availability, the required fertilization of potassium and measuring the supplying power of the soil at the plant age were also studied.
The obtained results could be summarized in the following:-
Soil Potassium Forms
1-Soils of the great groups greatly differed in K forms because of the difference in the quantity and the kind of clay mineral.
2- Soils of Vtt great group ( heavy clay soils ) had the highest amount of exchangeable K, while soils of Eott great group (sandy soils ) showed the lowest level of exchangeable K.
3- Soils of the great groups greatly differed in the soluble K and could be ordered according to soluble K as follows:
Vtt>Eftt>Epqt> Eott .
4- The available K is, in general, low in (Eott and Epqt) soil great groups
5- Soils of Vtt great group possessed the highest amount of available K whereas soils of Eott great group contained the lowest amount of.
6- All soil great groups have almost the same amount of total and non– exchangeable K (Lattice-K), but they markedly differed in their contents of soluble and exchangeable K.
7- The soil K forms were positively correlated with each soil particles fraction.
8- The exchangeable, non exchangeable (Lattice) and total K forms, positively and significantly correlated with clay fraction in both soil layers. Meanwhile they were negatively and significantly correlated to sand content.
9- Soluble K was positively and significantly correlated to the exchangeable K in all studied soil great groups.
10- The amount of soluble K in the surface soil layer of all studied soil great groups is controlled mainly by the amount of exchangeable K.
11- In most soil great groups, the K saturation values vary between 6.7 and to and 26.3%.
12- The values of step–K(non exchangeable K ) as extracted by 0.1 N nitric acid once and five times with 1.0 N nitric acid, were about 0.77 to 5.12 meq/100g soil in the soil samples. The highest amount of step-K was recorded for Vtt soil great group. Whereas soils of the Eott great group contained the lowest amount of step-K.
13- The study reported positive correlations between step-K and other forms of potassium, especially exchangeable potassium.
Q/I parameters, Gapon selectivity coefficient and Free Energy change (∆G):
(1) There was a positive correlation between K forms and ARKo
(2)-There was a positive correlation between the PBCK and the particle size fraction of the soils.
(3)The PBCK was positively correlated to the forms of potassium.
(4)The Gapon selectivity coefficient ranged from 1.09 to 3.10L mol-1.
(5)Changes of free energy varied from -2834.06 to -3986.92 cal.mol-1.
Effect of soil Incubation and K additions soil on Potassium Forms and Q/I parameters
1- Soil incubation led to an increase in all potassium forms, especially the exchangeable one.
2- Soil incubation resulting an increase of the PBCK and ARKo.
3- Soil incubation led to a decrease in the free energy change.
Effect of cropping and K Fertilization on soil potassium Forms and Q/I Parameters.
1-Plant growth resulted in decreases in the amounts of soluble, exchangeable and non-exchangeable K, of the studied soils.
2-Depletion in the exchangeable K form as a result of plant growth
was less than that of the soluble form of all studied soils. In the soils of the Eott , the depletion in both soluble and exchangeable K was equally acquired by plants .
3- Potassium fertilization showed a significant increase in dry matter yields of wheat and corn as well as weight as well as significant increases in PBCK, and ARK in all studied soil.
4-The potassium buffering capacity was decreased with increasing the plants age.
5-Potassium fertilization significantly increased the amount of soluble, exchangeable and non-exchangeable potassium.
6-The soluble K form was affected by plant uptake in the soil Eott great groups.
7-Soluble potassium was more affected by potassium fertilization than the other forms.
8-In all studied soil great groups, potassium fertilization had little or no effects on K bearing minerals (lattice) and total potassium.
9-Potassium fertilization had profound effects on the distribution of K into different forms in the studied soil group.
10-The shapes and the parameters derived from the Q/I relationship markedly differed among the soils of the great group.
11-The AR0K values increased with increasing the clay content, and they were affected to a great extent by the amount and mineralogy of the clay fraction in the soils. They significantly correlated with clay content and available K in soils.
12-The PBCK was well correlated to CEC and clay content.
13-The Q/I isotherm of soils of the great groups particularly Eott were affected by cropping,
14- Potassium fertilization exhibited remarkable effects on the shapes and parameters of the Q/I relationship of the studied soils.
15-In all studied soil great groups; the values of PBCK were remarkably increased with increasing the K application level.
16-In soil great groups, the values of AR0K were significantly correlated to both available K and total plant uptake of K. Therefore, the AR0K values may be used as an estimate for K availability in soil. Thus, they can be used to estimate the amount of potassium fertilizer needed for soils of each great group to furnish the proper amount of available K required for plant growth
.
17- The values of (∆G) obtained from all soils of great groups in Minia governorate verified that all soils were in need to potassium application.