Supplemental irrigation during dry spells could reduce maize yield losses in tropical semi-arid regions, notably in small farms. However, good quality water reserves are not sufficient to meet the demands of farming communities. Consequently, our objective was to evaluate the productivity and profitability of maize under different simulated rainfall scenarios, with and without supplemental irrigation (SI) with brackish water. The field experiments were carried out during the cropping seasons of 2018 and 2019 on Ultisol. The experiment followed a randomized block design in the split-plot scheme with four replicates. The plots were formed by simulating the water supply in the soil corresponding to four water scenarios (rainy, normal, drought and severe drought), and the sub-plots with or without SI with brackish water (Electrical conductivity of 4.5 dS m−1). Mean yields of green maize ears were 13,083, 11,532, 10,358 and 9,609 kg ha−1 for rainy, normal, drought and severe drought scenarios, as supplemented with brackish water. For the same treatments without SI the values were 11,394, 7,896, 3,913 and 1,374 kg ha−1, respectively. Data on farmer's income showed that under normal, drought and severe drought supplementation with brackish water becomes economically advantageous from 0.9, 1.0 and 2.4 ha, respectively, while maize cultivation without SI is not advantageous under the last two scenarios. For severe drought conditions, however, SI using brackish water reduced commercial yield by 27 % with negative effects on the farmers’ profitability. In this case, it is necessary to use water with either lower salinity or select salt tolerant crops.

The objective of this study was to evaluate the growth of forest species under conditions of salinity and water deficit. The experimental design was completely randomized in a triple factorial scheme with four forest species (Neem - Azadirachta indica A. Juss, ‘Aroeira’ - Myracrodruon urundeuva Fr Allemão, ‘Ipê’ - Tabebuia impetiginosa (Mart. ex. DC.) Standl and ‘Sabiá’ - Mimosa caesalpiniifoliaBenth), two salinity levels (1.2 and 8.6 dS m^-1) and two water regimes (with and without water restriction). Plant height, stem diameter, number of leaves, shoot dry matter, root dry matter and total dry matter were measured. For all the studied variables, there was statistical significance for the factors species (A) and salinity (B), individually. However, water deficit (Factor C) and the interaction among factors (A x B x C) did not cause any statistical effect. The 50% reduction in water replacement for the four species studied was not enough to cause significant damage to plant growth, with a mean reduction in dry matter production lower than 10%. It was observed that the tolerance index found varied according to the imposition of the stresses, being caused mainly by salinity. Based on shoot dry matter production, the species Neem behaved as moderately tolerant, while the other species were moderately sensitive to salinity. The applied water deficit was not enough to intensify the effects of the salt stress under the conditions of the present study.

Climate change significantly impacts agriculture and forage production, requiring the implementation of strategies toward increased water and energy use efficiency. So, this study investigated the yield of forage cactus (Opuntia stricta (Haw.) Haw) under different irrigation depths using brackish groundwater (1.7 dS m⁻¹), whose management was based on reference evapotranspiration (ETo) estimated by the Hargreave–Samani (HS) and Penman–Monteith (PM) equations. The research was conducted in Independência, Ceará, Brazil, under the tropical semi-arid climate. A randomized block design in a 2 × 5 factorial scheme was employed, varying the ET₀ estimation equations (HS and PM) and irrigation levels (0; 20; 40; 70; and 100% of total required irrigation—TRI). Growth, productivity, and water use efficiency variables were evaluated at 6, 12, and 18 months after treatment initiation. The economic analysis focused on added value, farmer income, and social reproduction level. The results showed no isolated effect of the equations or their interaction with irrigation depths on the analyzed variables, suggesting that irrigation management can be effectively performed using the simpler HS equation. Furthermore, there was no statistical difference between the means of 100% and 70% TRI as well as between 70% and 40% TRI for most variables. This indicates satisfactory crop yield under deficit irrigation. Dry matter productivity and farmer income at 12 months resulting from complementary irrigation with depths between 40% and 70% of TRI were significantly higher than under rainfed conditions. The 70% depth resulted in yields equivalent to those at 100% TRI, with the social reproduction level being achieved on 0.65 hectares in the second year.

The split-root technique was used as a strategy to reduce saline stress on pepper. A completely randomized design with six treatments and four replicates was used. The treatments consisted of six saline water application strategies (T1 - salinized nutrient solution (S1 = 1.4 dS m^-1) during the whole cycle; T2 - salinized nutrient solution (S2 = 4.5 dS m^-1) throughout the cycle, T3 - S1 and S2 throughout the cycle, using two emitters and without splitting the root system, T4 - S1 and S2, using two emitters and splitting the root system by a plastic film, T5 - S1 and S2, using two emitters and splitting the root system, alternating the solutions every 15 days, T6 - S1 and S2, using two emitters and without splitting the root system, alternating the solutions every 15 days). Five fruit harvests were performed, and the plants were harvested at 85 days after initiation of treatments and evaluated for the following variables: leaf number, leaf area, plant height, stem diameter, shoot dry matter (stem + leaves + fruits), root dry matter, number of fruits, fresh fruit weight and fruit production per plant. Most of the variables were reduced by the salinity of irrigation water. The highest fruit yields were obtained using low-salinity water, with the mixture of non-saline and saline waters, and alternating biweekly when the root system was split, demonstrating the viability of these three techniques.

Resumo Objetivou-se avaliar a composição química e o fracionamento de carboidratos da palma forrageira submetida a diferentes estratégias de irrigação. Adotou-se delineamento em blocos com esquema fatorial de 5 x 2 x 4, sendo 5 lâminas de irrigação (0, 20, 40, 70 e 100 % da irrigação real necessária - IRN) e 2 métodos de estimativa da evapotranspiração (Penman-Monteith e Hargreaves Samani), com 4 repetições. Foi quantificada a composição química e realizado o fracionamento de carboidratos pelo modelo CNCPS. As médias e as interações foram comparadas pelo teste de Tukey a 5 %. Os componentes fibrosos, proteína bruta e fração lignificada dos carboidratos apresentaram interação (P<0,05) entre os modelos e as lâminas. Os teores de proteína bruta foram mais elevados em lâminas de irrigação menores. Os valores de NDT variaram de 69 a 71 % em todos os tratamentos, não diferindo entre as lâminas. A palma forrageira cultivar orelha de elefante apresenta adequada composição química mesmo quando cultivada em condições de sequeiro, ou em lâminas de irrigação baixas. Recomenda-se o uso de lâmina de irrigação de 20 % da IRN junto modelo proposto por Hargreaves & Samani.

The objective was to evaluate the chemical composition and carbohydrate fractionation of Opuntia stricta submitted to different irrigation strategies. A block design was adopted with a 5 x 2 x 4 factorial scheme, with 5 irrigation depths (0, 20, 40, 70 and 100 % of the real irrigation required - IRN) and 2 methods for estimating evapotranspiration (Penman-Monteith and Hargreaves Samani), with 4 repetitions. The chemical composition was quantified and carbohydrate fractionation was performed using the CNCPS model. Means and interactions were compared using the 5 % Tukey test. The fibrous components, crude protein and lignified fraction of carbohydrates showed interaction (P<0.05) between the equations and the irrigation depths. Crude protein contents were higher in lower irrigation depths. TDN values varied from 69 to 71 % in all treatments, without differing between depths. The fodder palm cultivar elephant ear has an adequate chemical composition even when grown in rainfed conditions, or in low irrigation depths. It is recommended to use an irrigation depth of 20 % of the IRN along with the model proposed by Hargreaves & Samani.