No abstract

The present work has aimed to evaluate phenology and productive performance of chamomile in a subtropical weather region, sown in different dates and spacings in between plants. The experiment took place in Santa Maria – RS with four sowing dates in the year 2017 (18/03, 28/04, 30/06 and 31/08) and seven spacings along plants in rows (5, 10, 15, 20, 25, 30 and 40 cm), spaced 30 cm between each other. Phenological observations were made every two or three days in two plants per portion while also accounting for the number of nodes in the main stem. The harvest of chamomile floral chapters was performed manually from the beggining of flowering and repeated biweekly until plant maturation. Productivity of dry floral chapters as well as content and productivity of essential oils were evaluated. It was established that sowing dates affect the productivity of dry floral chapters, content and productivity of essential oil from cv. Mandirituba chamomile, with the sowings of March 18th and April 28th presenting the highest values for such variables. Increasing the space between plants from the 10 cm line to 40 cm in lines spaced in 30 cm has shown a linear tendency of decreasing the productivity of dry floral chapters. Spacings between plants did not affect the phenological development of chamomile, however, sowing dates interfered in the thermal time of six evaluated subperiods regarding plastochron and the final number of nodes.

The objective of this study was to evaluate the effect of leaf wetness on the severity of septoria leaf spot in sunflower. The experiments were performed in two sowing dates in November and January in Santa Maria, RS. Sunflower inoculation was carried out with the Septoria helianthi isolate, with subsequent assessment of disease severity, progress and cypsela yield. The treatments were composed of different periods of 0, 8, 12, 16, 20, 24, 28 and 32 hours of artificially applied leaf wetness. Variables influencing the disease were observed during the cycle, such as mean air temperature, mean relative air humidity and daily-accumulated rainfall. The greater the leaf wetness the greater the severity and the area under the disease progress curve. Meantime, the healthy leaf area duration has an inverse relation with leaf wetness duration. The yield also decreases with greater leaf wetness duration and the yield reduction reaches 100% in the plants exposed to the longer leaf wetness periods.

The overseeding technique allows the establishment of a crop before the harvest of an overseeded crop at the end of the cycle. It aims at making a better use of more favorable seasonal climatic conditions and the intensification of cultivation systems, with the possibility of obtaining another harvest in less time. This work aimed to verify if it is possible to establish the Brassica napus crop in overseeding with the phenological stages at beginning of grain filing (R5) and beginning of soybean physiological maturation (R7) in the Central region of the state of Rio Grande do Sul. The study was performed in a Humid Subtropical climate, in Santa Maria, RS. A randomized block design was used, in a 4 x 2 factorial arrangement with 4 replications, with four seed Brassica napus densities (3, 6, 12, and 18 kg ha-1) and two developmental stages of the soybean crop (R5 and R7), in addition to the control treatment sown in rows directly on the straw right after soybean harvest (3 kg ha-1- standard). The plant density, yield components, and grain yield were measured. The canola crop is not established when overseeded in the soybean stage R5. The seed density of 6 kg ha-1 achieved the recommended plant density for the canola overseeded in stage R7 of the soybean crop. The 6 kg ha-1 density stood out as the best treatment performed in the R7 stage of the soybean crop.

The knowledge of the variables specific leaf area and leaf area index is important for direct or indirect quantification of plant growth, development and yield. However, there is a lack of these information due to the difficulty in measuring the leaf area of chamomile. Measuring leaf area by direct methods, such as the use of leaf area integrator is a very laborious and time consuming activity because the plant has many leaves and with small size. The use of leaf dry matter is a promising variable for the leaf area estimation. As an important measure to evaluate plant growth, the present study aimed to obtain a model for chamomile leaf area estimation through leaf dry matter. The experiment was conducted in two sowing dates (March 18 and June 30, 2017) at different plant densities (66, 33, 22, 16, 13, 11 and 8 plants m-2). The leaves of chamomile plants were collected in the plant vegetative and reproductive phases. The leaf area determination was performed using the electronic integration method of leaf area. The specific leaf area was 133 cm2 g-1, with no differences between sowing dates, plant densities and phenological phases of plant collection. The leaf area measured with the electronic leaf area integrator exhibited high correlation with chamomile leaf dry matter and the resulting model of leaf area data by the integrator presented optimum performance. This model is indicated for leaf area determination of chamomile when there is availability of leaf dry matter data.