Showing papers by "Eduardo Fávero Caires published in 2018"

A Novel Phosphogypsum Application Recommendation Method under Continuous No-Till Management in Brazil

Abstract: 1987 No-till is defined as a system of seeding crops into untilled soil by opening a narrow slot, trench, or band with just the sufficient width and depth to confer proper seed coverage; no other soil tillage is performed in this system (Phillips and Young, 1973). Residues from previous cash crops or green manure cover crops should remain undisturbed on the soil surface after seeding. In this system, crop rotation and cover crops are essential practices (Derpsch et al., 2010). Continuous no-till systems have stood out as one of the most effective strategies to improve agricultural sustainability and minimize soil and nutrient losses due to erosion in tropical and subtropical regions (Hobbs et al., 2008; Lal, 1995). No-till systems are used across 111 million hectares worldwide (Derpsch et al., 2010). In southern Brazil, the development of no-till conservation agriculture in the early 1970s contributed greatly to the increase in agricultural production. Currently, Brazil is a leading country regarding the adoption of the no-till system, which is used in more than 90% of the cash crop area in southern Brazil. No-till systems are known to cause chemical stratification, including pH stratification, with high pH levels being found in the upper few centimeters of the soil profile (Caires et al., 2005). Subsoil acidity is a serious problem worldwide (Fageria and Nascente, 2014). The low content of base cations, especially calcium (Ca), and aluminum (Al) toxicity in the subsoil affect root growth, restricting the plant’s capacity to access water and nutrients (Carvalho and van Raij, 1997). This issue is critical in Brazil because exchangeable Al is found in most cultivated soils within this country (Olmos and Camargo, 1976). Phosphogypsum (PG), a by‐product of the phosphoric acid industry, is largely available in several areas across the world. In Brazil, approximately 4.8 Tg of PG are produced each year (van Raij, 2008). When applied to the soil surface, PG moves down the soil profile during drainage, which increases Ca2+ supply and reduces the toxic levels of Al3+ (Sumner, 1995). As a result, root growth and the absorption of water and nutrients by plants roots improve (Caires et al., 2016; Carvalho and van Raij, 1997; Ritchey et al., 1980). In soils with very low Al3+ and low Ca2+ concentrations, calcium supply might be a limiting factor in root proliferation (Ritchey et al., 1982). Positive effects of PG are expected when subsoil acidity is an important growth-limiting factor. Thus, the application of A Novel Phosphogypsum Application Recommendation Method under Continuous No-Till Management in Brazil

Discriminating Biomass and Nitrogen Status in Wheat Crop by Spectral Reflectance Using ANN Algorithms

Abstract: Precision agriculture has the goal of reducing cost which is difficult when it is related to fertilizer application. Nitrogen (N) is the nutrient absorbed in greater amounts by crops and the N fertilizer application presents significant costs. The use of spectral reflectance sensors has been studied to identify the nutritional status of crops and prescribe varying N rates. This study aimed to contribute to the determination of a model to discriminating biomass and nitrogen status in wheat through two sensors, GreenSeeker and Crop Circle, using the resilient propagation and backpropagation artificial neural networks algorithms. As a result, a strong correlation to the sensor readings with the aboveground biomass production and N extraction by plants was detected. For both algorithms a satisfactory model for estimating wheat dry biomass production was established. The best backpropagation and resilient propagation models defined showed better performance for the GreenSeeker and Crop Circle sensors, respectively. Discriminating Biomass and Nitrogen Status in Wheat Crop by Spectral Reflectance Using ANN Algorithms