Effect of different doses of post-emergence-applied iodosulfuron on weed control and grain yield of malt barley (Hordeum distichum L.), under Mediterranean conditions

A study was carried out over a two year period (2009/2010 and 2012/2013) on an experimental farm in the Alentejo region (Beja), in southern Portugal where rainfed malt barley (Hordeum distichum L.) is sown at the end of autumn or beginning of winter (November– December). The aim of this experiment was to study the efficiency of the herbicide iodosulfuron-methyl-sodium to control post-emergence broadleaved weeds in this cereal crop. The malt barley crop was established using no-till farming. This technology provides the necessary machine bearing capacity of the soil to assure the post-emergence application of herbicides at two diferente weed development stages. The herbicide iodosulfuron-methyl-sodium was applied at three doses (5.0, 7.5, and 10.0 g a. i. · ha–1) and at two different broadleaved weed development stages (3 to 4 and 6 to 7 pairs of leaves), that also corresponded to two diferente crop development stages (beginning of tillering and complete tillering). The results indicated that early herbicide application timing provided a significantly higher efficiency for all the applied herbicide doses, but this better weed control was not reflected in a higher crop grain yield. The lack of a higher crop grain yield was probably due to a crop phytotoxicity of the herbicide, when used at an early application timing.

Análise conjunta de regressões : ajustamento e zonagem agrícola

A Análise conjunta de regressões, ACR, é uma técnica utitilizada para estudar a interação gentipo x ambiente baseada em regressões. Nesta técnica ajusta-se uma regressão linear por cultivar. Nestas regressões a variável controlada é o índice ambiental que mede a produtividade dos vários ambientes. Nas culturas anuais, os ambientes compreendem aos pares (local, ano). Os valores dos índices ambientais e dos coeficientes das regressões são ajustados simultaneamente. Até agora a ACR tem sido aplicada a uma única cultura de cada vez. Neste trabalho vamos procurar ultrapassar essa limitação através da modelação dos logaritmos dos índices ambientais tendo-se desenvolvido um modelo da forma: zi, j  v  l j  j , i  1,...,n, J  1,...,n onde zi , j é o logaritmo do índice ambiental para o i-essimo ambiente na j  essima cultura , v um valor médio geral , li j  essimo cultivar. o efeito do i  essimo local e  j o efeito do Ao utilizar esta modelação, os locais corresponderão a estações experimentais de forma a poder-se ter várias culturas no mesmo local. Ora, as estações experimentais são escolhidas por forma a serem representativas das regiões onde estão implantadas. Assim, os índices ambientais correspondentes às várias estações experimentais e, consequentemente, às respetivas regiões, pudesse ser utilizados para agrupar regiões contíguas com índices semelhantes obtendo-se assim, um elemento interessante para a Zonagem agrícola no que diz respeito às culturas que se trabalha. Pode-se ainda procurar uma Zonagem para grupos de cultivares. Por exemplo, adiante trabalharemos com dados da cevada e trigo os quais são cereais. ABSTRACT: Joint Regression Analysis, JRA, is one of the techniques for the study of genotypeXenvironment interaction based on the use of regressions .In JRA a linear regression of the yields of each cultivar on a controlled variable, the environment index ,is adjusted .The index miss erasures the productivity of each environment .In yearly cultures the environments correspond to the pairs (location ,years) .These indexes and the correlation coefficients are adjusted simultaneously. Up to now JRA has been applied to single crops .Now we try to overcome this restriction through modeling of the logarithms of the environmental indexes .We developed a model τ i , j = v + l j +λ j , i = 1,..., b, J = 1,...J where τ i , j is the logarithm of the environmental index for the i-th environment and the j-th crop , v is the general mean , li is the effect of the i-th environment and λ j is the effect of the j-th crop . When applying this model the location will correspond to experimental situations in order to have several crops in the same locations .Now experimental stations are chosen to be representative of the regions in which they are located .Then the l1 ,..., lb can be used to group contiguous regions with similar location effects .We thus get an useful tool for Agricultural Zoning for the crops we used or, even, for the group to which those crops belong . For instance we worked with barley and wheat that are cereals.