engleski

The magnesium concentrations and uptake by weed species

The aim of this experiment with glasshouse growing slicing cucumber (two vegetation’s in 1994, two different plant densities and two different weeds pressure) was to determine the effect of plant densities, weeds pressure, nutrients concentrations and nutrients removal on cucumber yield and interactions between nutrients concentrations of different weed species during vegetation’s. All weed samples were separated in two groups: plants younger than 20-38 days and plants younger than 50-98 days, depending on periods between each hoeing. The hoeing significantly influenced to the increase of cucumber yield and the highest yield was estimated on the plots with hoeing and with higher crop density (3, 57 plants/m2) in both vegetation (av. 4, 24 and 3, 70 kg/m2). Simultaneously, the lowest yield (av. 1, 62 and 2, 40 kg/m2) was on the plots without hoeing and with lower crop density (2, 38 plants/m2). The influence of hoeing and crop density on the final weed mass was quite opposite, because weeds produced 1, 95 and 0, 65 t DM/ha on the plots without hoeing and with lower crop density, and just 0, 43 and 0, 19 t DM/ha with hoeing and with higher crop density. The same relations were estimated with reference to magnesium uptake by weeds: 6, 95 and 3, 04 kg/ha compared with 1, 79 and 1, 02 kg/ha. Mg uptake by weeds was approximately the same as P uptake, but much lower than N, K and Ca uptake and much higher than Na, Fe, Mn, Zn and Cu uptake by weeds. The relations between concentrations of mentioned plant nutrients for total weed mass were the same as the relations between nutrients uptake. The Mg concentration in total weed mass was 0, 44%, in younger plants 0, 50% and in older plants 0, 43%. The dicotyledones had higher Mg concentrations (0, 47%) than monocotyledons (0, 39%). At the same time, the older dicotyledon plants had lower Mg concentrations (0, 45%) than younger dicotyledon plants (0, 52%), but with monocotyledon plants the concentrations were quite opposite (younger 0, 39% and older 0, 40%). Both analyzed monocotyledon weed species, Echinochloa crus-galli and Poa annua had higher Mg concentrations in older plants (0, 43% and 0, 31%) than in younger plants (0, 37% and 0, 38%). The highest Mg concentration had Amaranthus lividus (younger 0, 84% and older 0, 77%) and next was Stellaria media with 0, 51% Mg in younger and older plants. Galinsoga parviflora had 0, 33% Mg in younger plants and 0, 32% in older plants, what was almost equally to Cirsium arvense (younger 0, 31% and older 0, 30%). The increase of the part of Stellaria media, Amaranthus lividus and Echinochloa crus-galli in the total weed mass meant also the increased removal of Mg while Cirsium arvense by its higher part contributed to lesser removal of Mg.

magnesium; weed species; slicing cucumber

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