The efficiency of potassium fertilization on the morpho-physiology and nutrition of safflower was evaluated using different doses (0, 80, 160 and 240 kg ha−1) of potassium chloride (KCl) in a completely randomized design with four replicates. In the flowering phase, were performed morphological evaluations of plant height, number of leaves, number of branches, number of chapters and stem diameter; physiological evaluations of CO2 assimilation (A), stomatal conductance (g s), transpiration (E), internal carbon concentration (C i), water use efficiency (WUE) and carboxylation efficiency (CE), and nutritional evaluations of accumulation of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) in the leaves. After harvesting, the nutritional status of the grain was evaluated. The potassium fertilization favored the growth of the plants, as well as positively interfered in its physiology and in the concentration of K and N in the leaves, however, the dose 240 kg ha−1 of KCl provided lower accumulation of Ca and Mg in the leaves and lower A. All evaluated characteristics were optimized in plants fertilized with potassium in relation to the dose 0 kg ha−1 up to the maximum point, which varied from 107 to 167 kg ha−1 of KCl according to the variable response, with a subsequent decline. Therefore, the dose of 160 kg ha−1 of KCl can be recommended for cultivation of safflower in soils with low level of K.

Crops are constantly threatened by salinity. Nitric oxide (NO) is an attenuating agent for salt stress; however, the specific roles of NO in gas exchange and lettuce production are not well established. The objective of this study was to evaluate the application of different concentrations of sodium nitroprusside (SNP) as an agent to mitigate salt stress in lettuce plants. Lettuce seedlings in pots were subjected to irrigation without and with saline water (0.2 and 3.5 dS m⁻¹) and applications of different concentrations (0, 50, 100, 150, and 200 µM) of SNP, a NO donor. Saline stress negatively affected lettuce development with a reduction of 29.5% in leaf area, 6.3% in relative water content in the leaf, 17.2% in stem diameter, and 10.7% in dry matter mass in the control, but the application of SNP mitigated the deleterious effects of salt stress. Concentrations between 100 and 150 µM of SNP improved the photosynthetic metabolism of lettuce under salinity, with an increase of 46.7% in CO₂ assimilation and 42.3% in fresh matter mass. Pearson’s correlation showed that fresh matter correlated positively with CO₂ assimilation. Therefore, SNP can be used to mitigate salt stress in lettuce.

Cover crops (CCs) have demonstrated their significance in enhancing the agronomic and economic performance of corn in succession. In this paper, we assess the agronomic responses and short-term economic returns of adopting cover crops (CCs) for corn cultivation in the sandy soils of the semiarid region of northeast Brazil, with the aim of addressing the additional challenges of CCs adoption in semiarid regions. The field study was conducted in Arapiraca, Alagoas, under no-tillage conditions for two cropping seasons. A randomized complete block design was employed, comprising six CCs (sunn hemp, spectabilis, jack bean, pigeon pea, lab lab, and millet) treatments and one fallow, with 18 replications. The CCs were cultivated for 60 days before corn planting. Drip irrigation was applied during the grain-filling stage of corn growth. Over the two cropping seasons, the biomass and nutrient cycling of the CCs, corn yield, and economic returns were determined, as well as the total organic carbon (TOC) and Mehlich-1 extractable P levels in the soil after corn harvest. The grain yields with sunn hemp, spectabilis, and jack bean were superior (~10%) to that of the fallow (7.7 vs. 7.1 Mg ha⁻¹), irrespective of the cropping season. Sunn hemp exhibited a higher biomass accumulation and ensured greater nutrient cycling, except for K, while lab lab and millet displayed a similar potential, although substantial variations were observed between seasons. Under sunn hemp and jack bean, the TOC increased by ~9%, particularly in the second season. Regarding the available P, spectabilis and jack bean exhibited the highest levels, with an increase of ~74% compared to the fallow (~31.1 vs. 17.9 mg dm⁻³). Spectabilis and lab lab demonstrated more promising results, both agronomically and economically. However, millet and sunn hemp have the potential to reduce costs over multiple cropping seasons. Therefore, the adoption of cover crops is a sustainable and economically viable agricultural practice. However, it is essential to acknowledge that our results do not represent rainfed conditions and require further investigation.

No Brasil, o feijão é um dos principais alimentos básicos da população devido elevado potencial energético, destacando-se tanto na produção para subsistência quanto para a agricultura empresarial, por ser uma cultura sensível ao déficit ou excesso de água no solo. Objetivou-se avaliar diferentes lâminas de água aplicada à cultura do feijoeiro em relação à evapotranspiração da cultura. O experimento foi conduzido em área pertencente à Universidade Federal de Alagoas/Campus Arapiraca, em condições de campo, durante o período de Agosto a Novembro de 2016, utilizando a cultivar carioca, com densidade de plantas de 240 mil por hectare. Foram analisadas as lâminas de água de acordo com a evapotranspiração da cultura, em cinco níveis de água (25, 50, 75, 100, 125%). Foram avaliadas área foliar, diâmetro do caule, comprimento do caule, número de vagens por planta, comprimento da vagem e largura da vagem. Os dados foram submetidos a análises de variância e regressão, utilizando o teste F (p ≤ 0,05) para verificar a significância. A partir da análise de variância constatou-se diferença significativa entre os tratamentos em todas as variáveis analisadas. Constatou-se que os níveis de irrigação inferiores a 100% da evapotranspiração da cultura afetaram negativamente as variáveis analisadas, inibindo o crescimento, com maior intensidade na área foliar e no número de vagem.