Sugarcane productivity and economic viability in response to planting density.

Planting with higher density in sugarcane is one of the practices used to overcome low productivity. However, this planting material is equivalent to 25% of the total cost of production, being one of the main expenses for cultivation. In this sense, the present work aims to evaluate the productivity and economic viability of sugarcane as a function of planting density. The experiment was carried out at Usina Monte Alegre in the municipality of Mamanguape, Paraíba, Brazil, from March 2021 to January 2022 with the variety RB92579. Seven planting density were studied: T1: 7 gems m-1, T2: 10 gems m-1, T3: 12 gems m-1, T4: 11 gems m-1, T5: 15 gems m-1, T6: 17 gems m-1, T7: 24 gems m-1, in randomized blocks with four replications. Growth, productivity and economic viability were evaluated. The highest productivity of cane and sugar, 77.69 ton ha-1 and 10.390 ton ha-1, respectively, was with planting density of 17 and 24 gems-1. While the minimum productivity of cane (61.313 ton ha-1) and sugar (7.924 ton ha-1) was recorded at sowing density of 7 and 11 gems-1. However, cultivation density with 7 and 10 gems m-1 were the ones that provided the highest profitability around 50%, followed by density of 12, 15 and 17 gems m-1 with an average of 45% profit and 11 and 24 gems m-1 with the lowest proportion of profit on average 38%. The cultivation with 17 gems m-1 of cane provides in cane-plant, variety RB92579, greater productivity with a profit rate of 45%, being the most suitable.

The physiological quality of Vigna unguiculata L. seeds shows tolerance to salinity.

Salinity reduces feijão-caupi production, and the search for tolerant varieties becomes important within the agricultural context, as, in addition to being used in the field, they can be used in genetic improvement. The objective was to for a identify variety that is tolerant to salinity considering the physiological quality of seeds and seedling growth. A 2 × 4 factorial scheme was used, referring to the varieties Pingo-de-ouro and Coruja, and four electrical conductivities of water (0; 3.3; 6.6 and 9.9 dS m-1). The physiological quality of seeds and the growth of seedlings were analyzed, in addition to the cumulative germination. The Pingo-de-ouro variety showed no germination, length of the shoot and root, dry mass of the shoot and root compromised up to electrical conductivity of 6 dS m-1 in relation to 0.0 dS m-1. On the other hand, the Coruja variety showed reduced germination, increased shoot and root length. The creole variety Pingo-de-ouro proved to be tolerant to salinity.

Agronomic parameters of sugarcane under planting densities in different cultivation cycles.

Low density sugarcane plantation (LDSP) has been implemented by some sugarcane producers in Brazil, aiming to save seeds and operational costs. The study was carried out in the municipality of Areia, Paraíba, Brazil. Five planting densities were used, varying from 5 to 25 m-2 of buds arranged in randomized blocks, with four replications. Data were measured annually over three cultivation cycles (2017 to 2020), during which the field was fertilized with NPK and the harvests were carried out manually without prior burning. The lower planting density presents higher productivity only in the cane plant (101.03 t ha-1) due to the higher plant height (2.37 m) and the higher number of stalks (11 stalks m-2), suggesting that these variables are due to the greater availability of light, water and photosynthate. However, there is a drastic reduction in sugarcane yield for this lower population in the 2nd ratoon by up to 65.62%, which is correlated with number of stalks per meter. We demonstrate the agronomic viability of LDSP in the population of 10 buds m-2 in relation to conventional planting of sugarcane until the 2nd ratoon. Data are important for future studies to present additional considerations for other production factors, such as the effects of mechanized harvesting and the management of nutrients and water, assessing the sustainability of this large-scale planting system.

Filter cake increases sugarcane yield.

Sugarcane cultivation stands out in Brazilian agribusiness, covering more than eight million hectares for the production of sugar, ethanol, and by-products. Fertilization is one of the limiting factors in sugarcane yield, for which filter cake is a viable solution to meet plant nutritional needs. This study aimed to assess the effect of enriched filter cake on gas exchange and yield in RB041443 sugarcane, cultivated in soils of the coastal tablelands of Paraíba, Brazil. The experiment was conducted in the Monte Alegre S/A sugarcane mill, in the municipality of Mamanguape, using a randomized blocks experimental design, with 12 treatments (T1- cake, T2- cake + MAP, T3- cake + gypsum, T4 - cake + phosphate, T5- cake + bagasse, T6- cake + MAP + gypsum, T7- cake + MAP + phosphate, T8- cake + MAP + bagasse, T9- cake + gypsum + phosphate, T10- cake + gypsum + bagasse, T11- cake + phosphate + bagasse, and T12- control (only MAP)), and 4 replications, totaling 48 plots. A significant effect (5% probability) was also observed for the variables number of leaves and tons of stem per hectare (TSH). T1- cake, T4- cake + phosphate, T6- cake + MAP + gypsum and T10- cake + gypsum + bagasse, had the best results for TSH, with yields greater than 140 t ha-1. Regarding stomatal conductance, the highest values were obtained in T6 and T8, which, together with T11, had the highest gs values. Concerning the internal carbon concentration, T1, T2, T6, and T8 stood out. T6 also had a significant effect on transpiration. From this study, it was concluded that the use of enriched filter cake as a base fertilizer in sugarcane culture contributes to increasing the yield of the RB041443 variety, generating positive responses for plant gas exchange, being T1 and T10 indicated to increase the production in the sugar-energy sector.

Influence of essential oils on the quality of Vigna unguiculata L. (Walp.) seeds compared by traditional method, image and multivariate analysis.

The extracts of medicinal plants are used for the treatment of seeds in order to reduce the action of phytopathogens and increase the vigor of the seeds. Currently, computerized image analysis has been used to assess the physiological quality of seed lots. The objective was to evaluate the efficiency of the Vigor-S® software in the evaluation of the physiological quality of cowpea seeds treated with essential oils, comparing with a traditional test and the principal component analysis. Two cowpea cultivars were analyzed, BRS Tumucumaque and BRS Guariba, treated with doses of natural extracts of Alfavaca, garlic, horsetail, citronella and pyroligneous acid. The traditional method consisted of evaluations for germination, first germination count, seedling emergence, emergence speed index, accelerated aging, fresh matter and dry matter of seedling and the image analysis for: seedling length, growth index, uniformity index, vigor index, and germination. A Principal component analysis was applied to reduce the number of variables. Horsetail, Alfavaca and citronella extracts were efficient in increasing the physiological quality of the seeds of at least one cultivar. The Vigor-S® software proved to be efficient compared to traditional tests to assess the physiological quality of seeds. Principal Component Analysis is an ally to identify the best extracts and doses to be used. The image analysis method proved to be effective when compared to the traditional method and can therefore be used.