The aim of this study was to develop mathematical models to estimate the leaf area of common bean (Phaseolus vulgaris) in irrigated and non-irrigated water regimes from linear dimensions. An experiment was carried out in a completely randomized design with a 3×2 factorial arrangement (three cultivars: Triunfo, Garapiá and FC 104; two water regimes: irrigated and non-irrigated) with 25 replicates each. A total of 523 trifoliates were collected throughout the crop cycle. The length (L, cm) and width (W, cm) of the central leaflet of the trifoliate were measured and their product (LW) (cm²) calculated. Then, the leaf area of these trifoliates was determined by digital photography methods using ImageJ® software, and using leaf discs. The number of samples required to estimate the leaf area of a trifoliate was determined to define which method is the most accurate to be used as the real leaf area in generating equations to estimate the leaf area in common bean. The relationship between area by digital photographs and the dimensions of the central leaflet of the trifoliate (L, W and LW) was fitted by linear, quadratic and power models. Subsequently, the predictive capacity of the equations was assessed by the root mean square error (cm2 trifoliate-1), mean absolute error (cm2 trifoliate-1), index of agreement and Pearson’s correlation coefficient. Sample size varied between cultivars, water regimes and evaluation methods. It is more appropriate to use the leaf area provided by ImageJ® as real for comparison purposes in generating models to estimate leaf area from linear measurements, in common bean. The general equation LA = 1.092L1.945 can be used in the tested regimes without accuracy losses.

Several authors report that potassium (K) is the nutrient absorbed in greater amounts by gerbera plants. Thus, objective of determining the concentration of Kin the solution of substrates for growing potted gerbera, quantified by the Cardy Horiba C-131 and an atomic absorption spectrophotometer, correlating them with each other and with the plant leaf content. The experiment was carried out in a greenhouse. The experimental design was in randomized complete blocks using a 5×2 factorial scheme (5 substrates/2 cultivars) and four replications. Cherry and Red gerbera cultivar seedlings with four final leaves were transplanted into pots, filled with the substrates and acclimated for 30 days. After acclimation, the K content in the substrate solution extracted by the “PourThru” methodology was evaluated every two weeks using the Cardy Horiba C-131 portable ion meter and an atomic absorption spectrophotometer, as well as the K content in the leaves of gerbera plants. The solution of the commercial substrate had higher concentrations of K in relation to the others in the two forms of measurement, which is directly related to the high initial contents of the nutrient in this substrate. This is directly related to the high initial K contents in the substrate. Greater values of K were obtained for the cultivar Red, both in the solution and in the leaves. The K concentration of the substrate solution cultured with gerbera plants quantified by the Cardy Horiba C-131 and atomic absorption spectrophotometry correlated significantly with each other and showed a low correlation with the content of this nutrient in the plant tissue.

Os substratos são utilizados na maioria dos cultivos em plantas ornamentais. Entre suas características essenciais, destaca-se o valor do potencial hidrogeniônico (pH), que pode influenciar a disponibilidade de nutrientes às plantas, podendo favorecer sua absorção, dificultar e ainda causar fitotoxidez. Apesar da sua importância, as informações que auxiliem na sua manutenção para adequar às necessidades das plantas são escassas. Desse modo, o presente trabalho foi conduzido com o objetivo de avaliar a neutralização da acidez em substrato de casca de pinus com diferentes granulometrias. O experimento foi conduzido em casa de vegetação, em delineamento experimental de blocos ao acaso com 5 doses de calcário dolomítico (5, 10, 15, 20 e 25 g L-1), 5 granulometrias de casca de pinus (<4mm; 4-2mm; <2mm; 2-1mm; <1mm), 4 tempos de incubação (10, 20, 30 e 40 dias) e 4 repetições. Os valores de pH da solução do substrato foram determinados a cada 10 dias, utilizando o método de diluição do 1:5.Os valores de pH do substrato diferiram entre as diferentes granulometrias, doses de calcário e dias de incubação. As menores granulometrias, de <1mm e de 1-2mm apresentaram maiores valores de pH. O aumento das doses de calcário resultou em aumento do pH, enquanto o aumento do tempo de incubação, resultou em decréscimo do pH. Os substratos com diferentes granulometrias de casca de pinus devem receber quantidades de calcário distintas para adequar os valores de pH. Não se recomenda utilizar o substrato na primeira semana após a aplicação do calcário devido à instabilidade do pH, independente da granulometria.

ResumoAs variações na temperatura do ar ocasionam consequências diretas na produção agrícola do Brasil, cuja economia é baseada neste setor em vários estados. O estudo pode auxiliar no planejamento agrícola a fim de aperfeiçoar este processo. O objetivo deste trabalho foi caracterizar a temperatura do ar para a região de Cachoeira do Sul no Rio Grande do Sul (RS). Utilizaram-se dados de 2007 a 2016 do Instituto Nacional de Meteorologia (INMET) da estação meteorológica A813 (Vaisala, MAWS 301; lat: -29º52'; long: -52º23'; alt: 107m). Calculou-se a temperatura média, mínima e máxima mensal e anual, além das temperaturas médias sazonais, temperaturas mínimas e máximas absolutas e a amplitude térmica. Foram analisados os anos com El Niño (). As médias da temperatura foram comparadas à Normal Climatológica 1961-1990. Verificou-se que a temperatura média anual foi de 19,1ºC (±0,5ºC), permanecendo próxima à normal. A temperatura média mínima apresentou aumento e a máxima, decréscimo. A temperatura em anos de La Niña apresentou redução, entretanto em anos de El Niño, não houve diferença. O conhecimento destas informações pode subsidiar o planejamento com relação à organização do agricultor, como o manejo do solo e a implantação bem-sucedida de novas culturas. Palavras-chave: Agricultura. El Niño. Oscilação Sul. Amplitude térmica. Abstract Climatic characterization of Cachoeira do Sul (Rio Grande do Sul) and adjacent municipalities regarding air temperatureThe variations in the air temperature have direct consequences in the agricultural production of Brazil, whose economy is based in this sector in several states. The study can aid in agricultural planning in order to perfect this process. The objective of this work was to characterize the air temperature for the Caracterização climática da região de Cachoeira do Sul (Rio Grande do Sul) quanto à temperatura do ar

The influence of water deficit on plant physiological and biochemical responses as measured by the fraction of transpirable soil water (FTSW) has not been investigated in cultivars developed by the world's largest soybean producer. This information can help obtain plants with improved tolerance to the abiotic stress that most affects soybean production in Brazil, enabling adaptation to edaphoclimatic conditions to enhance the crop's yield potential. We aim to determine the FTSW threshold for transpiration and evaluate changes in the growth, physiological activities, and biochemical and antioxidant responses of soybean cultivars. Three trials were sown on 11/19/2018 (T1), 12/28/2018 (T2), and 9/9/2019 (T3), representing almost the entire soybean sowing window in Brazil. The estimated FTSW threshold values were 0.33, 0.29, and 0.31 in T1; 0.35, 0.41, and 0.43 in T2; and 0.31, 0.49, and 0.45 in T3 for cultivars BMX GARRA IPRO, DM 66I68 RSF IPRO, and NA 5909 RG, respectively. In the three trials, NA 5909 RG showed the greatest height. The POD enzyme was activated in non-irrigated plants in T2 only in cvs. DM 66I68 RSF IPRO and NA 5909 RG. We conclude that cvs. DM 66I68 RSF IPRO and NA 5909 RG showed a more efficient stomatal control, conserving soil water for a longer time, which indicates greater tolerance to water deficit.

The objective of this work was to evaluate the response of the Garapiá, Triunfo, and BRS-FC104 bean (Phaseolus vulgaris) cultivars to the water deficit represented by the fraction of transpirable soil water (FTSW). The experimental design was completely randomized in a 3×2 bifactorial arrangement (cultivars × irrigation and no irrigation). Transpiration, growth, and yield were evaluated in the crop season and off-season. In the crop season, with a low atmospheric air demand (below 15 hPa in 55% of the days), 'Garapiá' presented early stomatal closure with the critical FTSW (FTSWc) of 0.36, but had the same yield as 'Triunfo', whose stomata closed late (FTSWc = 0.23). In the off-season, with a high atmospheric air demand (greater than 15 hPa in 83.3% of the days), 'Garapiá' presented an early stomatal closure (FTSWc = 0.17) and a higher yield (392.2 kg ha-1 more than 'Triunfo'). In the crop season and off-season, 'Garapiá' showed tolerance to water deficit in the reproductive period. Water deficit resulted in lower values of height, shoot dry mass, root dry mass, and leaf area. Both 'Garapiá' and 'Triunfo' showed a high yield in the crop season, but only 'Garapiá' in the off-season. 'Garapiá' presents tolerance to water deficit, with efficient stomatal control and high growth and yield.

Rice (Oryza sativa L.) is the main staple food of more than 50% of the world’s population. However, global production may need to increase by more than 70% before 2050 to meet global food requirements despite increasing challenges due to environmental degradation, a changing climate, and extreme weather events. Rice production in Ecuador, mainly concentrated in lowland tropical plains, declined in recent years. In this paper, we aim to calibrate and validate Kobayashi’s ‘Very Simple Model’ (VSM) and, using downscaled corrected climate data, to quantify the potential impact of climate change on rice yields for Ecuador’s two main rice-growing provinces. The negative impact is expected to be highest (up to −67%; 2946 tons) under the Representative Concentration Pathway (RCP) 8.5, with a lower impact under RCP 2.6 (−36%; 1650 tons) yield reduction in the Guayas province. A positive impact on yield is predicted for Los Ríos Province (up to 9%; 161 tons) under RCP 8.5. These different impacts indicate the utility of fine-scale analyses using simple models to make predictions that are relevant to regional production scenarios. Our prediction of possible changes in rice productivity can help policymakers define a variety of requirements to meet the demands of a changing climate.

The objective of this study was to characterize the development of chia plants sown at different dates, and to determine the relation between the duration of the development cycle and the final number of leaves and the leaf appearance rate on the main stem. A field experiment was conducted in the agricultural year of 2016/2017 in five sowing dates (09/22/16, 10/28/16, 01/03/17, 02/08/17 and 03/24/17) in the edaphoclimatic conditions of the central region of the RS, Brazil. A randomized block design with four replicates was used. For each sowing date, the duration of the vegetative and reproductive phases in days and in °C day (Tb = 11 °C), the final number of leaves and the phyllochron of the main stem were determined. The duration of the vegetative phase of chia plants in days and in ºC day varies between the sowing dates, with shorter duration in late sowings in response to the photoperiod reduction. The vegetative phase represents the largest part of the total development cycle in early sowing dates, being overcome by the reproductive phase in late sowing dates (02/08/17 and 03/24/17). The phyllochron for chia varies from 36.23 (very late sowing) to 59.88 ºC day (early sowing). Later sowing has a smaller final number of leaves accumulated in the main stem due to the shorter duration of the vegetative phase.