Intercropping of castor bean and sugarcane under irrigation: part 2: yield and agronomic indices

Intercropping can be an alternative to maximize yields of castor bean and sugarcane. This work aimed to investigate the yields and agronomic indices of castor bean and sugarcane in intercropping system. The experiment was carried out in the field, at the Ponta da Serra Farm, in the municipality of Queimadas-PB, Brazil. Treatments resulted from a 4 x 4 factorial arrangement, with twelve replicates. The irrigation depths (drip system) tested were: 50, 75, 100 and 125% crop evapotranspiration, and the spacings used for castor bean were: (1 x 0.5 m), (1 x 1 m), (1 x 1.5 m) and (1 x 2 m), that is, 20,000, 10,000, 6,666 and 5,000 plants per hectare, respectively, with total area of 2,880 m², each one with twelve plots of castor bean spacing. The following variables were evaluated: land equivalent ratio and relative crowding coefficient. For all irrigation depths tested, sugarcane yield increased linearly with the increment in castor bean spacing. The highest value of land equivalent ratio was found at 1 x 0.5 m spacing, and the lowest values of relative crowding coefficient for sugarcane occurred at 1x 0.5 m spacing for all irrigation depths.

Competition between rice (Oryza sativa L.) and (barnyardgrass (Echinochloa crus-galli (L.) P. Beauv.) as affected by methanol foliar application

Pot experiment was conducted in Iran, to evaluate the effect of methanol on competition between rice (Oryza sativa) and barnyardgrass (Echinochloa crus-galli). The experiment was conducted as a randomized complete block design with a factorial treatment arrangement and three replicates. Factors were two aqueous methanol foliar applications (0, and 14% v/v) and five rice: barnyardgrass ratios (100:0, 75:25, 50:50, 25:6, and 0:100). Replacement series diagrams for aboveground dry weight illustrated that 'Shiroudi' was more competitive than barnyardgrass as averaged across methanol foliar applications. When methanol was not sprayed, the lines for 'Shiroudi' and barnyardgrass intersected at 75:25 rice: barnyardgrass ratio, but when methanol was sprayed at 14% v/v, the lines for 'Shiroudi' and barnyardgrass intersect at the left of the 75:25 rice: barnyardgrass mixture proportion. These indicate that methanol application reduced competitive ability of 'Shiroudi' against barnyardgrass for aboveground biomass accumulation. At the same time, Methanol foliar application significantly reduced the relative crowding coefficient of 'Shiroudi' while simultaneously it significantly increased the relative crowding coefficient of barnyard grass. This indicates that methanol foliar application reduced the competitive ability of 'Shiroudi' against barnyardgrass for shoot biomass accumulation. This experiment illustrated that foliar spray of aqueous methanol can not be recommended for rice under weedy conditions .

Competition between Calamagrostiscanadensis and Epilobiumangustifolium under different soil temperature and nutrient regimes

The relative competitive abilities of Calamagrostiscanadensis (Michx.) Beauv. and Epilobiumangustifolium L. were tested in two sets of replacement series experiments. Both species were grown in monocultures and a range of mixtures in 25-cm pots. In the first set, substrates were held at either 9 or 21 °C; in the second set the pots were fertilized at high or low rates. In the 21 °C treatment C. canadensis was more competitive than E. angustifolium (relative crowding coefficient for C. canadensis towards E. angustifolium was 2.88), while there were little competition differences in the cool soil conditions. Under the cool soil temperatures, however, E. angustifolium showed higher vegetative reproduction than under the warm soil conditions. In the high nutrient conditions, C. canadensis was more competitive than E. angustifolium (relative crowding coefficient for C. canadensis towards E. angustifolium was 5.84). There was little competition in the low nutrient experiment. These experiments indicate that if both species colonize a site simultaneously, C. canadensis will outcompete E. angustifolium under most conditions, as suggested from field observations of earlier researchers.