Saulo Augusto Quassi de Castro

The aim of this study was to assess the efficacy of herbicides in association to control Rottboellia exaltata and Ipomoea quamoclit during pre-emergence while also to evaluate the potential impact on the sugarcane. The experimental design employed a randomized block with seven treatments and four replications. The treatments were: 1 - no herbicide application; 2 - indaziflam + sulfentrazone; 3 - indaziflam + diclosulam; 4 - indaziflam + tebuthiuron; 5 - flumioxazin + diclosulam, 6 - flumioxazin + pyroxasulfone and 7 - clomazone + sulfentrazone. The evaluated parameters were: percentage of weeds control, green coverage percentage (Canopeo (R) system), weed biomass (g m(-2)), itchgrass height, and sugarcane tiller. Several herbicide associations have been proven effective alternatives for managing itchgrass and cypressvine morningglory. The most successful treatments for itchgrass control were indaziflam + tebuthiuron (100%) and indaziflam + diclosulam (97%), whereas for cypressvine morningglory, the betters were indaziflam + sulfentrazone (97%), indaziflam + diclosulam (98%), indaziflam + tebuthiuron (97%), flumioxazin + diclosulam (94%), and clomazone + sulfentrazone (96%). All treatments reduced the weed biomass, with indaziflam + tebuthiuron being the safest option for protecting sugarcane.

Purpose: Nitrogen fertilizer management is an important agricultural tool that must be optimized to promote sustainable practices since the nitrogen-fertilizer recovery by plants (NRP) is low, leading to nitrogen losses to the environment. In sugarcane, N-fertilization has been investigated over the years but little attention has been given to N-fertilizer application methods. Sugarcane crop production and environmental impact regarding N-fertilizer application methods (i.e., applied onto the sugarcane straw layer and incorporated into the soil) were investigated in the present study aiming to achieve an environmental-friendly cropping system. Methods: Sugarcane yield and NRP, N₂O emissions, relevant components of the soil microbiological community and N-fertilizer retention in soil layers were quantified. The experiment was carried out in field conditions where N-fertilizer application methods using ¹⁵N-labelled ammonium nitrate (¹⁵NH₄¹⁵NO₃) were compared to a control treatment with no N-fertilization. Results: Incorporation of N-fertilizer into the soil increased the sugarcane yield by 17% (two-year average) compared to N-fertilizer applied onto the sugarcane straw layer, which was similar to control treatment. There was an increase in NRP-fertilizer of 79% due to the application of N-fertilizer incorporated into the soil. Furthermore, soil incorporation of N-fertilizer decreased N₂O emission by 22% with the fertilizer N emission factor reduced four-fold. The N₂O emissions were mostly associated with ammonium-oxidizing bacteria (AOB). Conclusions: Our results show that application of N-fertilizer incorporated into the soil is an environmental-friendly N-fertilization management which will improve agricultural sustainability and reduce environmental impacts. Graphical

Foliar N‐fertilization (FNf) has emerged as a promising approach to synchronize plant nitrogen (N) demands and application timing, reducing the N losses to the environment associated with traditional soil‐based fertilization methods. However, limited information exists regarding the effectiveness of FNf in sugarcane. This study aimed to optimize FNf in sugarcane by evaluating N‐fertilizer recovery by the plant (NRP) and assessing potential toxicity effects. Four sugarcane genotypes were subjected to FNf using ¹⁵N‐urea at five nitrogen concentrations. NRP was assessed at five time points for roots, stalk, old leaves, ¹⁵N‐urea‐fertilized leaves (¹⁵NL), and unexpanded leaves (UEL). Leaf scorching, indicating FNf toxicity, was analyzed using morpho‐anatomical and histochemical techniques. The results showed that FNf promoted high NRP, with an average recovery of 62.3%. Surprisingly, the redistribution of ¹⁵N‐urea did not follow the nitrogen uptake rate by sugarcane leaves, with an average of 41.3% of the total‐NRP. The stalk emerged as the primary sink for ¹⁵N‐urea, followed by the UEL. Genotypes differed in the leaf scorching intensity, which increased with higher concentration of ¹⁵N‐urea. Genotypes also differed in the ¹⁵N‐urea uptake rate, down‐regulated by the N content in the ¹⁵NL. These findings emphasize that by carefully choosing the appropriate genotype and nitrogen concentration, FNf can significantly enhance N‐fertilizer uptake, resulting in potential environmental and economic benefits.

To obtain good control of wild poinsettia (Euphorbia heterophylla) in post-emergence in sugarcane crop, we evaluate the herbicides association on post-emergence of E. heterophylla and the ratoon cane selectivity. The experimental scheme was in randomized blocks with 6 treatments and 4 replications. The treatments were: control; ametryn + mesotrione + sulfentrazone (1,500 + 144 + 800 g i.a ha^-1); ametryn + mesotrione + diclosulan (1,500 + 144 + 200 g i.a ha^-1); ametryn + mesotrione (2,500 + 144 g i.a ha^-1: Highest dose); ametryn + mesotrione (2,000 + 144 g i.a ha^-1: Lowest dose) and ametryn + mesotrione + diuron (1,000 + 144 + 1,250 g i.a ha^-1). The percentage of control, dry mass, height and percentage of germination of E. heterophylla and injury level, yield and technological quality of sugarcane were evaluated. The best control of E. heterophylla was: ametryn + mesotrione +sulfentrazone; ametryn + mesotrione + diclosulan and ametryn + mesotrione (Lowest dose). As for the ratoon cane selectivity the best yield was achieved with the association ametryn + mesotrione +diclosulan. An appropriate association of herbicide molecules provides successful control of E. heterophylla, especially the association of sulfentrazone or diclosulan together with ametryn and mesotrione.

Introduction: The contrasting weather conditions throughout the sugarcane harvest period in south-central Brazil (April to November) influence fertilization management in sugarcane ratoon.Methods: Through field studies carried out over two cropping seasons, we aimed to compare the performance of sugarcane at sites harvested in the early and late periods of the harvest season as a function of fertilizer sources associated with application methods. The design used in each site was a randomized block in a 2 x 3 factorial scheme; the first factor consisted of fertilizer sources (solid and liquid), and the second factor consisted of application methods (above the straw, under the straw, and incorporated into the middle of the sugarcane row).Results: The fertilizer source and application method interacted at the site harvested in the early period of the sugarcane harvest season. Overall, the highest sugarcane stalk and sugar yields at this site were obtained with the incorporated application applying liquid fertilizer and under straw applying solid fertilizer, with increments of up to 33%. For the site harvested in the late period of the sugarcane harvest season, the liquid fertilizer promoted a 25% higher sugarcane stalk yield compared to the solid fertilizer in the crop season with low rainfall in the spring, while in the crop season with normal rainfall, there were no differences between treatments.Discussion: This demonstrates the importance of defining fertilization management in sugarcane as a function of harvest time, thereby promoting greater sustainability in the production system

Foliar fertilization is a potential tool to increase the use-efficiency of nitrogen (N) fertilizers. However, whilst leaf scorching has frequently been reported, the underlying physiological processes are not clear. In the present work, we investigate the intensity of leaf scorching as affected by the balance between ammonium assimilation and accumulation. Leaves were sprayed with urea–ammonium nitrate (UAN) solution without surfactant or applied liquid droplets of urea in different N concentrations with surfactant. UAN solutions without surfactant containing >10% N caused leaf scorching already after 24 h and the severity increased with the N concentration. The same pattern was observed 3 days after the application of urea solutions containing >4% N together with surfactant. The scorching was accompanied by a massive increase in foliar and apoplastic ammonium (NH₄⁺) concentration. Moreover, the activity of glutamine synthetase (GS), most pronouncedly that of the chloroplastic isoform (GS2), decreased a few hours after the application of high N-concentrations. Along with this, the concentration of glutamate—the substrate for GS—decreased. We conclude that leaf scorching is promoted by NH₄⁺ accumulation due to a limitation in N assimilation capacity.