Data/hora: 24/06/2024 21:14:24

Biblioteca(s): 	Embrapa Cerrados; Embrapa Soja; Embrapa Solos; Embrapa Trigo.	
Data corrente: 	29/05/1992	
Data da última atualização: 	02/11/2019	
Autoria: 	WIETHÖLTER, S.	
Título: 	Predicting potassium uptake by corn in the field using the strontium nitrate soil testing method and a diffusion-controlled uptake model.	
Ano de publicação: 	1983	
Fonte/Imprenta: 	Madison: University of Wisconsin, 1983.	
Páginas: 	244 p.	
Idioma: 	Inglês	
Notas: 	Thesis PhD.	
Conteúdo: 	The rate of potassium uptake by plants grown in soil is limited by the rate of diffusion to the roots. Calculation of diffusion rates requires a knowledge of the soil solution concentration (C[indice]1i), buffer power (b) and diffusion coefficiente (D). The Gapon equation was used to calculate selectivity coefficients for K+, Na+, Ca2+, Mg2+, Mn2+ and Al3+ from concentrations in 0.004M Sr(NO3)2 extracts and from amounts exchangeable in M NH4Cl. For a proposed routine method, C[indice]1i, b and D were calculated from the Sr(NO3)2 equilibration. This required the use of estimated selectivity coefficients obtained from regression of pH, OM, clay and cation ratios on determined selectivity coefficients. A constant-root-absorbing-power (constant-[alfa]) diffusion equation was applied to a root model that assumed an effective radius (a[indice]e) of 0.07 cm (root radius + root-radius + root-hair length). A root length:plant dry matter ratio of 1000 cm g[elevado a]-1 dry matter was used, and each root segment was assumed to effective in K+ uptake for the same time period. Initially, uptake was assumed to occur only within the root-hair cylinder, the time of effective depletion being estimated with a steady- state, interacting-root model. After depletion of the root-hair cylinder, diffusion from outside was assumed to start, with radius equal to a[indice]e and [alfa] estimated from the Michaelis-Menten equation. Root hairs had to be effective for 4-5 days to satisfy the total K+ uptake estimated from K+ content of the ear leaf. Uptake of K+ by corn at 51 field sites throughout Wisconsin was best predicted by the diffusion model (r[elevado]2=0.58 with determined selectivity coefficients and 0.51 with estimated coefficients). The K+ concentration in Sr(NO3)2 also correlated well (r[elevado]2=0.49). Exchangeable K+ was a por predictor (r[elevado]2=0.13). The diffusion model applied to data from Sr(NO3)2 equilibration appears promising as a routine soil testing method for K+. With this approach, fertilizer recommendations could be based on on theoretically-derived estimates of K+ uptake rather than on empirically-derived relationships.	
Palavras-Chave: 	Applied Statistics; Estatistica aplicada; Maize; Mathematical model; Modelos matematicos.	
Thesagro: 	Absorção; Milho; Potássio; Solo; Zea Mays.	
Thesaurus Nal: 	absorption; corn; potassium; soil.	
Categoria do assunto: 	--	
Registro original: 	Embrapa Trigo (CNPT)	
Exemplares: 	CNPS - (4075-1) - ADD - TS - -- - 83005 - WIE/83 - 1997.00541 - DIS
CNPSO - (15214-1) - ADD - TS - -- - 32/83 -  - 32/83 - DIS
CPAC - (20165-1) - ADD - TS - -- - T039/83 - WIE - T039/83 - DIS
CNPT - (30088-1) - UPC - TS - -- - TS-0508 -  - 0508 - DIS