ABSTRACT. Water and saline stresses are the main factors affecting agricultural production in semiarid regions. The tolerance of forage cactus to water and salt deficit makes it a promising solution, in particular Nopalea cochenillifera. The growth curves for species facing these conditions can provide useful information supporting the cultivation and management of natural populations and carry significant biological importance as growth rate assessment contributes to maintaining species viability. The objective of this study was to estimate the plant height and linear dimensions (length, width, and thickness) of N. cochenillifera Giant Sweet clone growing under water and saline stress. The experiment design was completely randomized, comprising a 4 × 4 factorial, with four water and four salinity levels; there were four replications. In order to estimate plant height in N. cochenillifera Giant Sweet clone as a function of the accumulated thermal sum, generalized additive models for location, scale, and shape (GAMLSS) were used to determine water level, saline level, length, width, and thickness. We constructed models using four distributions: the Weibull, Gumbel, Logistic, and Box-Cox power exponential distributions. The models were evaluated using global deviation and the generalized Akaike criterion. The Box-Cox power exponential proved to be the most effective in estimating N. cochenillifera height. This model enabled information relevant to practical environmental management to be obtained, as it precisely defined the optimum salt application and the required amount of replacement water, together with the cladode width for each plant growth stage using the accumulated thermal sum.

Resumo Objetivou-se avaliar o efeito de diferentes níveis de adubação potássica no crescimento inicial de clones de palma forrageira (Nopalea cochenillifera Salm Dyck). O experimento foi conduzido durante seis meses, disposto em delineamento em blocos ao acaso, em esquema fatorial 5x2, sendo cinco níveis de adubação potássica (0, 250, 500, 750 e 1000 Kg de K2O ha-1) e dois clones de palma forrageira (Doce Gigante e Doce Miúda), com quatro repetições. Foi plantado um cladódio por vaso (unidade experimental) com capacidade para 7 kg de solo (24 x 17 x 23 cm). Ao longo do período experimental, foram avaliadas as características estruturais das plantas, tais como altura e largura de planta, comprimento, largura, espessura e perímetro de cladódio, bem como contabilização do número de cladódios total e por ordem de surgimento. Ao final do experimento avaliou-se a biomassa, para determinação do rendimento de massa fresca (MV) e seca (MS) da parte aérea e do sistema radicular. Após a determinação de MS, determinou-se o teor potássico nos tecidos vegetais. Os dados foram submetidos a ANOVA e, caso necessário, ao teste de Tukey a 5% de significância. A adubação potássica e os clones de palma forrageira não exerceram influências significativas nas variáveis avaliadas durante a condução experimental. A adubação potássica não influencia as características estruturais, produtivas e teor potássico no crescimento inicial de clones de Nopalea cochenillifera.

Abstract The objective was to evaluate the effect of different levels of potassium fertilization on the initial growth of forage cactus (Nopalea cochenillifera Salm Dyck) clones. The experiment lasted six months, arranged in a randomized block design, in a 5 x 2 factorial scheme, with five levels of potassium fertilization (0, 250, 500, 750, and 1,000 kg of K2O ha-1) and two forage cactus clones (Little Sweet and Giant Sweet), with four replicates. One cladode was planted per pot (experimental unit) with a capacity of 7 kg of soil (24 x 17 x 23 cm). During the experimental period, the plants' structural characteristics were evaluated, such as plant height and width, length, width, thickness, and perimeter of the cladode, as well as accounting for the number of total cladodes, and in order of appearance. At the end of the experiment, biomass was evaluated to determine the fresh matter (FM) and dry matter (DM) yield of the aerial part and the root system. After determining the DM, the potassium content in the plant tissues was determined. The data were submitted to ANOVA and, if necessary, to the Tukey test at a 5% significance level. The potassium fertilization and the forage palm clones did not exert influences based on the variables evaluated during the experimental conduction. Potassium fertilization does not influence the structural and productive characteristics and the potassium content in the N. cochenillifera clones' initial growth.

ABSTRACT. Agricultural production in semi-arid regions is limited due to water availability. In addition, the water quality available for irrigation is often compromised due to the high salt content present. Millet is a forage species considered tolerant to water deficit and moderately salt tolerant. In view of the above, the objective was to evaluate the growth of millet under water and saline stress associates. The experiment was carried out in a randomized block design, in a 4x3 factorial scheme, composed of four levels of water replacement, based on crop evapotranspiration (ETc): 25%.ETc, 50%.ETc, 75%.ETc and 100%.ETc and three levels of water salinity (0.03, 2.0 and 4.0 dS m-1). With 25%.ETc independent of salinity, all morphological characteristics of millet were affected, occurring death of plants in the initial growth phase. In the absence of salt and greater availability of water, greater plant growth occurred. With respect to salinity, there was a reduction in the increment of all variables evaluated, with the highest reduction at the highest saline level (4.0 dS m-1). Water and salt stresses, when associated, reduce the growth of millet, since concentrations above 2.0 dS m-1 and less than 50%.ETc compromise its full development, providing declines in yield.

ABSTRACT. The forage palm is one of the main forages of ruminants in semiarid regions. Measurements of leaf area are required in agronomic studies because they are one of the main parameters used to evaluate plant growth. The objective of this study was to validate and define the best models for estimating the area and weight of Giant Sweet clone (Nopalea cochenillifera) forage cladodes in a non-destructive way based on the linear dimensions of length, width and thickness. There were 432 randomly measured cladodes at 550 days after planting. The length, width and thickness of each cladode were measured using a digital calliper. The cladodes were weighed individually. The cladode area was calculated by the gravimetric method. The power regression model was the most efficient method to explain the cladode area as a function of the product of length by width, while the gamma model was the most efficient method to explain the weight of cladodes as a function of the product of length by width and thickness. The power model, R C A ̂ = L W 0.982, and gamma model, W C ̂ = 0.536 T + 0.028 L W, were used to determine the area and weight of Nopalea cochenillifera Giant Sweet clone cladodes, respectively, based on the values of linear dimensions measured independently of the order of the cladode.

ABSTRACT. Leaf area measurements are of the main parameters used in agronomic studies to evaluate plant growth. The current study used a non-destructive method based on linear leaf dimensions (length and width) to select the regression model to estimate millet (Pennisetum glaucum) leaf area. For two millet genotype (IPA BULK 1 BF and ADR 300) 128 randomly-chosen leaves were measured at different vegetative growth stages. Measures of length and width of each leaf were made using digital calipers. Leaf area was measured using a gravimetric method. The best-fit leaf area estimation model was selected via linear, potential and gamma regression models. Leaf area values varied from 3.02 to 209.21 cm2. The average value was 95.31 cm2. The potential regression model exhibited lower residual sum of squares and Akaike's information criterion and similar determination coefficient and Willmott index. Thus, potential regression was more efficient in explaining the leaf area of millet, independent of the genotype, when compared to other models evaluated in this research. Length (L) and width (W) could be used in the following potential regression model Y ̂ = 0.879 L W 0.971to estimate millet leaf blade.