Phenology and thermal requirements of the species Cyperus difformis L. in southern Brazil

Cyperus difformis L. is a Cyperaceae, annual, of natural occurrence in marshy environments in southern Brazil, considered a weed in irrigated rice crops. Studies on its development are scarce, especially regarding its cycle and thermal requirements. Therefore, the objective of this work was to determine the base temperature, the thermal sum and the duration of the different sub-periods of the biological cycle of the species. The experiment was carried out at the Campus of the Universidade Federal de Santa Maria – UFSM, Santa Maria, Rio Grande do Sul, in four sowing seasons. In a completely delineated design and factorial scheme involving five soil water conditions (water depth and 50% soil water retention capacity [WRC]) from the sowing, water depth and 50% WRC introduced 21 days after emergence and 100% WRC during the whole cycle, with six repetitions each. Each experimental unit consisted of a cultivated in pot plant with 11 L capacity filled with soil. The cycle of the plants was subdivided into the sowing-emergence sub-periods, emergence-emission of the floral tassel and emission of the floral-maturing physiological tassel, being estimated the thermal requirements for the species. The conditions of the soil water condition the base temperature, the sum of the degree-days and the duration of the species cycle. The base temperature varies for each treatment, the sum of degrees-day decreases with the water deficit and the plants under flood accelerate the biological cycle.

Modelos não-lineares para a estimativa da produção de tomate do tipo cereja / Nonlinear models for estimating cherry tomato yield

RESUMO: Os objetivos do trabalho foram ajustar modelos de regressão não-linear para a estimativa da produção de frutos de tomate tipo cereja e identificar o tamanho da parcela com melhor poder de explicação e ajuste dos modelos, utilizando dois ensaios de uniformidade em estufa plástica. Os modelos ajustados foram o logístico e o de von Bertalanffy, para peso médio de frutos, número médio de frutos e de cachos acumulado nas múltiplas colheitas e com diferentes tamanhos de parcela. Os modelos apresentaram estimativas semelhantes entre si e as mesmas estimativas dos parâmetros em todos os casos de tamanho de parcela. Os modelos de regressão não-linear estudados descrevem satisfatoriamente o comportamento da produção de frutos de tomate tipo cereja cultivado em estufa plástica. Parcela constituída de duas plantas para ensaios em estufa plástica de 250m2 e de três plantas em estufa plástica de 200m2 proporcionam bom poder de explicação nas estimativas dos parâmetros dos modelos.

ABSTRACT: The aim of this paper was to test nonlinear regression models for estimating the cherry tomato production and to identify the plot size with better fitting quality and adjustment of the models, using two uniformity trials in greenhouse. The logistic and von Bertalanffy models were used on variables, as the means fruit weight, the means number of fruits and bunches accumulated in the multiple harvests and with different plot sizes. The models presented similar estimates for all parameters in all plot sizes studied. The nonlinear models adequately describe the behavior of the production of cherry tomato fruits cultivated in greenhouse. Plots constituted by two and three plants, respectively in trials with greenhouse of 250 m2 and 200 m2, provide a good fitting quality in the models adjustment.