Chemical Desiccation in the Preharvest of Cowpea: A Study of How the Time of Application Interferes in the Enzymatic and Physiological Aspects of Seedlings from Desiccated Plants.

Chemical desiccation in the preharvest of grains and seeds is commonly used in production fields. Using herbicides for this purpose is a viable alternative to reduce beans' exposure to adverse crop conditions. Our objectives were to evaluate (1) the efficacy of herbicides for accelerated defoliation of cowpea, (2) the impact of herbicide application on antioxidant enzyme activity and protein and amino acid contents in seeds, and (3) the effects of different herbicide application schedules on the physiological aspects of seeds. In the first experiment, in addition to the control treatment (without herbicides), seven herbicides and two mixtures were applied at night: diquat, flumioxazin, diquat + flumioxazin, glufosinate ammonium, saflufenacil, carfentrazone, diquat + carfentrazone, atrazine, and glyphosate. Diquat and its mixtures showed greater efficacy in anticipating the harvest. Flumioxazin and diquat alone reduced amino acid content by 61.72 and 51.44%, respectively. The same trend was observed for total soluble proteins. The activity of antioxidant enzymes (CAT, POD, PPO) increased, indicating oxidative stress caused by diquat and flumioxazin. In the second experiment, we tested three application times (6 a.m., 12 p.m., 6 p.m.) with diquat, diquat + flumioxazin, and diquat + carfentrazone. The lowest damage to chlorophyll a was at 6 a.m.; other times reduced photosynthetic pigments and increased carotenoid content. Total soluble sugars decreased by 27.74% with nocturnal application of diquat + flumioxazin. Our data indicate that herbicide use for desiccation affects seed quality. These findings highlight the need for selecting appropriate herbicides and application times. Future research should explore long-term impacts on crop yield and quality.

Physiological Responses of Minimally Processed Sweet Potatoes Grown with Increasing Doses of Phosphate Fertilizer.

The present work aimed to study oxidative damage and protection, phenylpropanoid metabolism, and the quality of minimally processed colored sweet potatoes cultivated with increments in P2O5 fertilization. Sweet potato was cultivated with 0, 60, 120, 180, and 240 kg ha-1 of P2O5. The roots were harvested, and the P content in the roots and leaves was quantified. The roots were minimally processed and kept for 20 days at 5 °C. In general, the roots that were fertilized with P2O5 showed a higher content of the analyzed variables. The highest P dosage in the soil increased the P content in roots and leaves and the agro-industrial yield. Roots cultivated with P2O5 showed a higher content of hydrogen peroxide, phenolic compounds, vitamin C, yellow flavonoids, anthocyanins, and carotenoids, antioxidant capacity by the DPPH method, and higher activity of the enzymes polyphenol oxidase, peroxidase, and phenylalanine ammonia lyase. These results demonstrated the role of phosphorus in protecting against oxidative damage due to the accumulation of bioactive compounds, thus improving the physicochemical quality of minimally processed orange sweet potato.

Agronomic performance of cassava fertilized with phosphorus doses

We have evaluated the agronomic performance of table cassava cultivars fertilized with phosphorus doses in the Brazilian Semiarid Region. Two agricultural crops were grown at the Rafael Fernandes Experimental Farm, Mossoró, RN, from June/2018 to April/2019 and from June/2019 to April/2020. The experimental design was in randomized blocks, arranged in subdivided plots, with four replications. In the plots, doses of phosphorus were applied (0, 60, 120, 180 and 240 kg P2O5 ha-1), and in the subplots, the table cassava cultivars (Água Morna, BRS Gema de Ovo, Recife and Venâncio). The following were evaluated: dry matter of leaf, stem, and commercial root; harvest index; commercial root number; commercial productivity and aerial part productivity. The cultivars used had high root and aerial part productivities indicating that their irrigated cultivation is appropriate under the conditions of the Semiarid region of Rio Grande do Norte. The cultivars Água Morna, BRS Gema de Ovo and Recife are more efficient in the use of phosphorus, obtaining high productivity even in the absence of phosphate fertilization. The cultivar Venâncio is more responsive to phosphate fertilization, as it needs an input of this nutrient to increase its productivity.

Efficiency of Nitrogen Use in Sunflower.

The large variation in the response of sunflower to nitrogen fertilization indicates the need for studies to better adjust the optimum levels of this nutrient for production conditions. Our objectives were to analyze the agronomic yield of sunflower cultivars as a function of nitrogen fertilization; indicate the cultivar with high nitrogen use efficiency; and measure the adequate N dose for sunflower through nutritional efficiency. The completely randomized block design with split plots was used to conduct the experiments. The treatments included five nitrogen rates being allocated in the plots and the four sunflower cultivars. To estimate the nutrient use efficiency in the sunflower, we measured agronomic efficiency (AE), physiological efficiency (PE), agrophysiological efficiency (APE), apparent recovery efficiency (ARE), and utilization efficiency (UE). The results indicate that all cultivars had a reduction in AE due to the increase in N doses in the first crop. For PE, the highest values were observed for Altis 99 during the 2016 harvest. In that same harvest, Altis 99 had the highest APE. The dose of 30 kg ha-1 provided greater ARE for all cultivars in both crops, with greater emphasis on BRS 122 and Altis 99. The cultivation of cultivars Altis 99 and Multissol at a dose of 30 kg ha-1 in is recommended semiarid regions.

Phosphate Fertilization as a Modulator of Enzymatic Browning in Minimally Processed Cassava.

This study proposes to relate the increase in phosphorus (P) supply in the soil, via phosphate fertilization, to oxidative damage and protection, phenylpropanoid metabolism, and enzymatic browning in minimally processed cassava. The roots were grown with 0, 60, and 120 kg ha-1 P2O5. The roots were harvested, and the yield and P content in the root, stem, and leaves were quantified. The roots were minimally processed and stored for 12 days at 5 °C. The higher supply of P in the soil increased the P content of roots and stems but not the agro-industrial yields. Roots grown at 120 kg ha-1 P2O5 showed higher detection of hydrogen peroxide, which was accompanied by increased phenolic compounds, soluble quinones, and antioxidant capacity and increased activities of the enzymes superoxide dismutase, catalase, ascorbate peroxidase, polyphenol oxidase, and peroxidase. The present study thus demonstrates the role of phosphorus application, induction of the synthesis of phenolic compounds, and quality of fresh-cut cassava.