Data/hora: 22/09/2024 07:39:16

Biblioteca(s): 	Embrapa Soja.	
Data corrente: 	04/10/2000	
Data da última atualização: 	09/03/2006	
Autoria: 	VOLL, E.; GAZZIERO, D. L. P.; BRIGHENTI, A. M.; ADEGAS, F. S.; OLIVEIRA, M. C. N.	
Título: 	Sampling size of weed seed banks.	
Ano de publicação: 	2000	
Fonte/Imprenta: 	In: INTERNATIONAL WEED SCIENCE CONGRESS, 3., 2000, Foz do Iguassu. Abstracts... Corvallis: International Weed Science Society, 2000.	
Páginas: 	p.79.	
Idioma: 	Inglês	
Conteúdo: 	For quantitative studies of weed seed banks, in cultivated and uniformly managed soils, the number of soil samples to be taken to assure a satisfactory estimation of the seeds in the area, is crucial. In order to determine the number of soil samples needed for a required precision, experimental phots of 60 m2 (small plots) and farmers fields of 0.25-0.5 ha (large plots) were sampled and compared. Sets of 506 and 517 seed counts were computed for the small large plots, respectively. Sampling was conducted using 10 sub-samples/sample in small plots and 50 in th large plots. Samples were taken randomly, using a tubular soil sample of 5 cm diameter, up to a 10 cm soil depth. Soil samples were washed trough an inox sieve of 0.5 mm mesh, floated, and viable weed seeds identified by speciesand counted. Linear regression equations were established between means and variances of the weed species, allowing to calculate the numberof samples needed (n), as a function of the average number of seeds per sample (Xm), for two different precision levels (c.v.=20% or 40%). The equation nP = ((50712* (Xm)-1,147)/cv2) estimates the number of samples needed in the small experimental plots and nF = ((50759* *Xm)-0,717)/cv2)), the number in the farmers field large plots. I was estimated that for means between 500 and 1000 seeds m-2,taken at soil depth of 10 cm, and c.v. = 20%, a number of 9 to 4 soilsamples (10 sub-samples per sample), respectively, are neede for smaller plots. With a lower precision (c.v. = 40%), the number of soil samples needed varied between 2 and 1 samples (20 to 10 sub-samples), respectively. In considering the same number of seeds/soil sample for large plots, the number of required samples would be about tree times higher.	
Palavras-Chave: 	Banco de semente; Brasil; Parana; Planta daninha; Seed bank.	
Thesaurus Nal: 	Brazil; weeds.	
Categoria do assunto: 	--	
Registro original: 	Embrapa Soja (CNPSO)	
Exemplares: 	CNPSO - (12827-1) - UPC - PL - -- - RF 341 -  -  - DIS