M. K. Sinha

The relative efficiency of zinc carriers on growth and zinc nutrition of corn

SummaryA comparison of different zinc carriers showed that application of Zn-DTPA, Zn-EDTA, Zn-fulvate and ZnSO4 significantly increased the dry matter yield and zinc uptake by corn over the control treatment where no zinc was applied. The chelates in particular enhanced to a greater extent the uptake of both native and applied sources than that observed with ZnSO4 as the zinc carrier. Both the dry matter yield and zinc uptake by corn showed a positive and significant relationship with self-diffusion coefficient of zinc showing thereby that diffusion contributed mainly the supply of Zn from the ambient soil matrix to plant roots. The effectiveness of the chelates varied depending on their capacity to retain Zn in a soluble form in the soil solution.It is evident that zinc nutrition of plants in alkaline and calcareous soils can be more effectively regulated by both synthetic and natural chelates or organic manures which contain substantial amount of complexed zinc.

Composition and mineralogy of iron-manganese concretions from some soils of the Indo-Gangetic plain in Northwest India

Abstract Iron-manganese concretions from three reference soil series of the Indo-Gangetic plain of Punjab have been investigated for their composition, micromorphology and mineralogy. The data show that amounts of Fe, Mn, Co, Ni, Cu and Zn in the concretions are higher than in the surrounding soil matrix. The contents of Mn, Co and Ni increase and that of Fe decreases with the increasing size of concretions. Cu or Zn contents do not show any systematic differences with concretion size. A major portion of these elements is oxalate- and dithionite-extractable. A minor fraction is present in the silicate structure as well as in the pyrophosphate-extractable forms. The Fe and Mn compounds present in the concretions are x-ray amorphous. The concretions appear to have developed in situ.

Chemical equilibria and quantity—Intensity relationship of zinc in some acid soils of India

Abstract Laboratory studies were conducted to investigate the nature of chemical equilibria of zinc in some acid soils of Himachal Pradesh (India). The results indicated that one of the chemical reactions controlling zinc ion activity in the ambient soil solution may be represented by the equation: Si(OH) 4 + 2H 2 O ⇋ Zn(OH) 2 ( crys. ) + SiO 2 ( amorph. ) + 2H 3 O + Sequential extraction of 65Zn-equilibrated soils provided a measure of the intensity of its different forms and their relative contribution to the pool of potentially available zinc in such soils. Adsorption-desorption parameters have been derived from a quattitative treatment of these phenomena as defined by the Langmuir equation. A supply parameter, √ cq √K 1 K 2 , integrating the combined effects of quantity, intensity and buffering capacity has been derived from the adsorption studies. A linear relationship between the supply parameter and cumulative desorption of applied zind in these soils has been noted. The desorption of zinc from these soils is an exponential process. The solubility relationship of zinc is expressed in terms of the theory of simultaneous equilibria of competitive chemical reactions which obviates the necessity of assuming a single physico-chemical model in predicting and relating the activity of zinc in the ambient soil solution and its surface reactivity on solid phases in the immediate vicinity of plant roots to its ultimate transport and uptake by plants.

Physical and chemical characterization of soil and poultry litter humic and fulvic metal complexes.

SummaryHumic and fulvic-zinc complexes obtained from soil and poultry litter were characterized by I.R. spectroscopy, determination of stability constant and the free energy change associated with their formation. Infrared spectroscopy confirmed that both electrovalent, coordinate-covalent bonds of Zn2+ with the carboxylate, phenolic hydroxyl and amine groups lead to the formation of their stable complexes. This is evident from the changes in absorption bands at 1700 cm−1, 1725 cm−1, 1625 cm−1 and 1400 cm−1 of their infrared spectra.The stability constants of complexes are pH-dependent. Interaction of Zn with humic and fulvic acid involved the formation of mononuclear complexes. The values of stability constants of these complexes are lower than those reported earlier.The calculation of the free-energy change associated with salts and complex formation indicates the spontaneity of both reactions, although a higher probability of complex reaction than that of salt formation is evident. The implications of the complexation of metal ions by these naturally occurring polydisperse plyaanions in regulating the movement of metal ions from the ambient soil matrix to plant roots and biological system in terresterial and aquatic environments are indicated.

Effect of chelating agents on the kinetics of diffusion of zinc to a simulated root system and its uptake by wheat

SummaryThe kinetics of Zn diffusion to a simulated root system was investigated at a controlled rate of exudation of mobile chelating agents through porous ceramic tubes into a soil tagged with 65Zn tracer. The chelating agents enhanced the rate of Zn diffusion from the soil into the simulated root to varying extents depending upon their relative efficiency in increasing the concentration gradient of diffusible Zn. The rat eof Zn diffusion from the soil into the simulated root conformed to pseudo-first order kinetics. The uptake of Zn by wheat plants was significantly increased when a constant flux of DTPA, EDTA and FA (fulvic acid) into the 65Zn labelled soil was maintained during a 60 days growth period. A significant linear regression between the concentration of soluble Zn in soil and its uptake by wheat was observed. The calculated diffusive flux of Zn based on the assumption of a constant concentration of Zn at the root surface bore a curvilinear relationship with Zn uptake by wheat.

Effect of gypsum, pressmud, fulvic acid and zinc sources on yield and zinc uptake by rice crop in a saline-sodic soil

SummaryThe application of fulvic acid to a saline-sodic soil augmented the solubility of zinc by thousands fold. Zinc fulvate when applied at levels equivalent to that of zinc sulphate was more effective in enhancing diffusion of zinc in the soil. Application of gypsum, zinc sulphate and fulvic acid significantly increased dry matter yield and uptake of zinc by rice crop in a saline-sodic soil. Application of gypsum with pressmud or with fulvic acid and zinc sulphate resulted in significantly higher yield and zinc uptake than in other treatments.

Effect of zinc-amended poultry manure and zinc sulphate on the growth and uptake of zinc by corn (Zea mays L.)

SummaryA greenhouse experiment conducted to study the effect of different levels of Zn supplied through Zn-amended poultry manure and ZnSO4 on corn (Zea mays L.) indicated that both the sources significantly increased the dry matter yield and uptake of zinc. The zinc amended poultry manure at all levels of zinc application was more effective than ZnSO4 in this respect. The percent zinc in corn derived from the fertilizer and percent utilization of applied zinc from the Zn-amended poultry manure was higher than that from ZnSO4 when applied at equivalent levels.

Labile pool and selective distribution of zinc in soils

SummaryThe labile pool of zinc in alkaline soils was determined by the application of isotopic dilution principle under laboratory and greenhouse conditions using corn and wheat as experimental crops. Simultaneously, the selective distribution of65Zn isotope between the solid and solution phases in 0.1M CaCl2 was determined. The labile pool-selective distribution coefficient diagrams were used for delineating the soils into different categories of Zn availability. The variations of the parameters of zinc availability were related to the physical and chemical properties of the soils. The results indicated that the plants and the DTPA extractant removed forms of zinc that may not undergo isotopic exchange in indifferent electrolytes. The values of labile pool obtained by the laboratory and greenhouse methods were highly correlated. The selective distribution coefficient was related to the organic matter and clay contents of the soils (R=0.78). A comparison of the values of labile pool of zinc measured with corn and wheat crops indicated that the two crops differ appreciably in affecting the isotopic dilution of65Zn in their root zone. The results indicate that the greenhouse method of determining the labile pool of zinc may be used as a reference procedure for calibrating soil test methods that extract amounts of Zn equal or proportional to that removed by growing plants in alkaline soils. The DTPA procedure of determining the available Zn in such soils meets the requirements of a satisfactory soil test method. re]19760726

Organo-metallic phosphates: V. Complexation of zinc and phosphorus by humic compounds

SummaryHumic and fulvic acids extracted from a mollisol and manure were used to determine their zinc-complexing capacity by ion-exchange equilibrium method. The simultaneous chelation of phosphorus by organic-matter preparations in the presence of complexed zinc was also studied. The results indicated that phosphorus is bonded to humic and fulvic acids in the presence of complexed zinc. Phosphate ions in such complexes probably act as additional ligands in bridging the organo-metal units. The stability constants of zinc complexes increased whereas the free-energy change accompanying their formation recorded lower negative values in the presence of phosphorus and at higher pH. Zinc fulvic salts and complexes being less stable but mobile should enhance the movement of zinc ions to plant roots and yield of crops in deficient soils.

Parameters of availability of zinc in orchard soils in relation to zinc nutrition of apple

SummaryLabile pool, selective distribution coefficient and adsorption maxima of zinc were measured. Labile pool decreased while selective distribution coefficient increased with increasing depth in all soil profiles. The values of adsorption maxima of zinc corresponded to selective distribution coefficient. The relative efficiency of four extractantsviz 0.05M CA(NO3)2 0.1M Mg(NO3)2; 0.01M EDTA−NH4OAc and 0.005M DTPA-triethanolamine mixture in predicting the availability of native soil zinc to apple was tested. The correlation study indicated that all extractants are good index of zinc availability to apple trees. DTPA-extractable zinc is as efficient as its labile pool(E-value) in predicting the availability of native soil zinc to apple trees. This study also suggested that soil profile should be sampled upto a depth of 30–60 cm for providing a better prediction of availability of native soil zinc to apple trees.