O gladíolo, importante flor de corte, é uma planta herbácea e suas folhas apresentam formato de lança. Os objetivos do trabalho foram determinar um modelo matemático empírico que melhor estima a área da folha do gladíolo a partir de dimensões lineares e aplicar o modelo matemático para determinar o perfil vertical da área das folhas de diferentes posições na planta. Para isso foi realizado um experimento de campo em Santa Maria com quatro cultivares de gladíolo (Peter Pears, Rose Friendship, Jester e Amsterdã), sendo coletadas 50 folhas de cada cultivar, das quais mensuraram-se o comprimento (C) e a maior largura (L). Em seguida, fotocopiou-se cada folha em um scanner, calculando-se a área individual (AF) com auxílio de um software. A relação entre área e as dimensões das folhas foi ajustada no modelo potência e a capacidade preditiva das equações foi avaliada por várias estatísticas. Resultados indicam que o modelo AF = a (C.L) é o mais indicado para a estimativa da área foliar em gladíolo, podendo-se utilizar a = 0,644 para as quatro cultivares testadas. As menores folhas estão nas posições basais e apicais e as maiores, na posição intermediária da planta.

The objective of this work was to model, in the SimulArroz model, the three flood-irrigated rice (Oryza sativa) cultivars currently most grown in the state of Rio Grande do Sul, Brazil. The experiments to calibrate and validate the model were conducted in the municipalities of Cachoeirinha, Santa Maria, Uruguaiana, Santa Vitória do Palmar, and Cachoeira do Sul during four crop seasons. The number of leaves, phenology, aboveground dry matter biomass, and yield of each cultivar were evaluated. The results showed a slight overestimate of the R1, R4, and R9 stages; however, overall, the SimulArroz model had a good performance in simulating rice phenology for the three studied genotypes. Furthermore, the model had a reasonable accuracy in simulating aboveground dry matter and yield. The root-mean-square error (RMSE) for aboveground dry matter (leaves, stems, panicles, and grains) ranged from 0.5 to 3.0 Mg ha-1. For yield, the RMSE ranged from 0.8 to 1.3 Mg ha-1. The calibration of the SimulArroz model is efficient in simulating the growth, development, and grain yield of the most important flood-irrigated rice cultivars in Southern Brazil and can be used to estimate harvest forecast and yield potential, as well for yield gap studies.

This study quantified K uptake kinetic parameters in grass species Paspalum notatum, Paspalum urvillei and Axonopus affinis to associate them with growth. Ten milliliters (10 ml) of nutrient solution were collected in two-liter pots - with five repetitions in 24 hours - in order to determine K concentrations in the samples. Shoot and root dry matter, root length, volume, diameter and surface area, as well as kinetic parameters associated with nutrient uptake (Vmax, Km, Cmin and I) were determined. Species P. notatum was the one presenting the highest root, shoot and total dry matter production, as well as the highest root volume. P. urvillei recorded the highest K content, which may be associated with thinner roots and greater root surface area. A. affinis recorded the highest Vmax value, which led to greater K uptake efficiency.

Maize production in Brazil is notable for its high potential for agricultural expansion and extensive cropland areas. This study evaluated the current yield gap (Yg) in Brazilian maize production and investigated the potential impact of irrigation on closing this gap. Field experiments were conducted in three key maize-producing regions in Brazil to calibrate a crop model and obtain reliable data on yield potential (Yp) and water-limited yield potential (Yw) across different environments. Data on river basin flows were employed to ensure that irrigation would not result in the depletion of water resources for other uses. Our findings suggest that Brazil’s average actual yield (Ya) is 55.4 % below the Yp. It was determined that increasing irrigation levels is a viable method for achieving the potential maize yield without compromising available water resources. The average Yg is approximately 5.2 Mg ha^–1, indicating a potential production increase of 41.9 % without expanding cropland areas. Strategic planning is essential to balance increased production and expanded irrigation, particularly to avoid impacting regions with water scarcity. It is underscored that the focus should be on areas with sufficient water resources to close Brazil’s current maize Yg. The results from this study offer valuable data for decision-makers and policymakers to enhance maize production sustainably.

A maioria das cultivares semeadas no Sul do Brasil apresentam grupo de maturidade relativa (GMR) entre 4.5 e 7.0 e tipo de crescimento indeterminado. O objetivo do estudo foi detalhar o desenvolvimento vegetal, através do plastocrono e número final de folhas (NFF), de cultivares com diferentes GMRs e épocas de semeadura. Foram utilizadas 11 cultivares de soja com GMR variando de 4.2 a 8.2 e tipo de crescimento determinado e indeterminado em três anos agrícolas. Foram contados o número de nós visíveis e avaliado os estádios vegetativos três vezes por semana. O NFN varia de acordo com o fotoperíodo em que a planta é exposta na fase vegetativa e difere entre cultivares, de acordo com o GMR e tipos de crescimento, sendo os menores valores observados em semeaduras precoces (setembro) e tardias (janeiro e fevereiro).