Browsing by Author "Holzapfel, Eduardo"
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Item A satellite-based ex post analysis of water management in a blueberry orchard(2020) Holzapfel, Eduardo; Lillo-Saavedra, Mario; Rivera, Diego; Gavilán, Viviana; García-Pedrero, Angel; Gonzalo-Martín, ConsueloIn the scenario of current water scarcity caused by climate change and increasing water demand for food production, farmers must adapt their water management practices by shifting from supply-driven water management to demand-driven water management, considering trade-offs among quality, quantity and costs. Thus, agricultural practices must take full advantage of technology, research and development and adapt to local requirements. Nowadays, remote sensing is a useful tool for estimating crop water demand (evapotranspiration) as well as mapping their spatial and temporal variability. In this work, we present a new methodology that allows the user to audit (ex post) the irrigation strategies of a blueberry field in central Chile using a decision support system for irrigation decision called AquaSat® as the main tool. This tool combines satellite information with field data and provides spatially distributed information on crop water use for managing irrigation at a farm scale. The main contribution of this work is to detail a new approach for irrigation management through the comparison of volume of applied water, against evapotranspiration and potential demand. This procedure allows the user to audit current irrigation management and to determine the impacts on productivity. From our results, we can conclude that the applied water levels used at the farm during both seasons throughout of the irrigation sector were insufficient to reach the potential blueberries yield.Item Early Estimation of Tomato Yield by Decision Tree Ensembles(2022) Lillo-Saavedra, Mario; Espinoza-Salgado, Alberto; García-Pedrero, Angel; Souto, Camilo; Holzapfel, Eduardo; Gonzalo-Martín, Consuelo; Somos-Valenzuela, Marcelo; Rivera Salazar, DiegoCrop yield forecasting allows farmers to make decisions in advance to improve farm management and logistics during and after harvest. In this sense, crop yield potential maps are an asset for farmers making decisions about farm management and planning. Although scientific efforts have been made to determine crop yields from in situ information and through remote sensing, most studies are limited to evaluating data from a single date just before harvest. This has a direct negative impact on the quality and predictability of these estimates, especially for logistics. This study proposes a methodology for the early prediction of tomato yield using decision tree ensembles, vegetation spectral indices, and shape factors from images captured by multispectral sensors on board an unmanned aerial vehicle (UAV) during different phenological stages of crop development. With the predictive model developed and based on the collection of training characteristics for 6 weeks before harvest, the tomato yield was estimated for a 0.4 ha plot, obtaining an error rate of 9.28%.Item Effects of the number of drip laterals on yield and quality of apples grown in two soil types(2021) Lecaros-Arellano, F.; Holzapfel, Eduardo; Fereres, E.; Rivera, Diego; Muñoz, N.; Jara, J.The effects of water distribution patterns in drip irrigation on fruit production and fruit quality were evaluated during two seasons in two commercial orchards of Gala Brookfield apple trees, grafted on M.9 dwarf rootstock. Research was conducted at El Manzano farm, with a clay-loam soil irrigated three times per week, and in Santa Mercedes farm, with a stony loam soil irrigated daily. Both farms are located in the Central Valley of Chile. The farm irrigation system was modified to establish three treatments which differed in the number of drip laterals per row (one, two and four), with 4.0, 2.0, and 1.0 L h−1 emitters spaced at 50 cm in both farms, respectively. All treatments received the same amount of water per week in each farm, based on the technical criteria of the farm advisor. Applied water in each farm was compared against the water use estimated by the AQUASAT platform. In the clay-loam soil, the volume of applied water was similar to the AQUASAT estimate. However, in the stony loam soil applied water was less than that estimated by AQUASAT. The results showed significant differences in production among treatments which varied only in the volume of wetted soil. The best results pooled over the two years were obtained with one lateral per row (T1) in the clay-loam soil (yield of 59.3 t ha−1), and with four laterals per row (T3) in the stony loam soil which yielded 50.8 t ha−1. Higher yields were associated with a tendency of greater fruit numbers per tree in both farms. Fruit quality requirements for export (equatorial diameter > 60 mm, weight > 90 g) were achieved but not the firmness in the second season at the stony loam soil, due to an irrigation deficit. Our results in apple emphasize the need to wet sufficient soil volume under drip irrigation, regardless of irrigation amounts, in light textured soils in particularItem Estimation of Yield Response Factor for Each Growth Stage under Local Conditions Using AquaCrop-OS(2020) Kuschel-Otárola, Mathias; Schütze, Niels; Holzapfel, Eduardo; Godoy Faúndez, Alex; Mialyk, Oleksandr; Rivera, DiegoWe propose a methodology to estimate the yield response factor (i.e., the slope of the water-yield function) under local conditions for a given crop, weather, sowing date, and management at each growth stage using AquaCrop-OS. The methodology was applied to three crops (maize, sugar beet, and wheat) and four soil types (clay loam, loam, silty clay loam, and silty loam), considering three levels of bulk density: low, medium, and high. Yields are estimated for different weather and management scenarios using a problem-specific algorithm for optimal irrigation scheduling with limited water supply (GET-OPTIS). Our results show a good agreement between benchmarking (mathematical approach) and benchmark (estimated by AquaCrop-OS) using the Normalised Root Mean Square Error (NRMSE), allowing us to estimate reliable yield response factors ( Ky ) under local conditions and to dispose of the typical simple mathematical approach, which estimates the yield reduction as a result of water scarcity at each growth stage.Item Multiperiod Optimisation of Irrigated Crops under Different Conditions of Water Availability(01/10/2018) Kuschel-Otarola, Mathias; Rivera, Diego; Holzapfel, Eduardo; Palma, Cristian D.; Godoy Faúndez, AlexWe propose a nonlinear optimisation model which maximises profits by resource allocation on a monthly time scale, considering a monthly crop yield model. The proposed model was applied to six management scenarios (two seasonal and four monthly), nine conditions of water availability, and two situations of resource availability under Chilean conditions. These situations provided the same seasonal amount of resources, but different distributions over time. The model included improvements in water resource management such as water storage and water transactions, being the latter a monthly decision variable that can increase farmers’ profits. According to our results, monthly scenarios gave high profits, even better with appropriate resource distribution. When water costs are high, water transactions allow loss reduction of up to 50%. Regarding labour, the lack of availability is more critical than the wagesItem Simulation of Water-Use Efficiency of Crops under Different Irrigation Strategies(2020) Kuschel-Otárola, Mathias; Rivera, Diego; Holzapfel, Eduardo; Schütze, Niels; Neumann, Patricio; Godoy Faúndez, AlexIrrigation management is a key factor in attaining optimal yields, as different irrigation strategies lead to different yields even when using the same amount of water or under the same weather conditions. Our research aimed to simulate the water-use efficiency (WUE) of crops considering different irrigation strategies in the Central Valley of Chile. By means of AquaCrop-OS, we simulated expected yields for combinations of crops (maize, sugar beet, wheat), soil (clay loam, loam, silty clay loam, and silty loam), and bulk density. Thus, we tested four watering strategies: rainfed, soil moisture-based irrigation, irrigation with a fixed interval every 1, 3, 5, and 7 days, and an algorithm for optimal irrigation scheduling under water supply constraints (GET-OPTIS). The results showed that an efficient irrigation strategy must account for soil and crop characteristics. Among the tested strategies, GET-OPTIS led to the best performance for crop yield, water use, water-use efficiency, and profit, followed by the soil moisture-based strategy. Thus, soil type has an important influence on the yield and performance of different irrigation strategies, as it provides a significant storage and buffer for plants, making it possible to produce “more crop per drop”. This work can serve as a methodological guide for simulating the water-use efficiency of crops and can be used alongside evidence from the fieldItem Water Scarcity and the Impact of the Mining and Agricultural Sectors in Chile(2016) Aitken, Douglas; Rivera, Diego; Holzapfel, Eduardo; Godoy Faúndez, AlexChile contains some of the driest areas in the world, yet human activities in these areas require large volumes of water, the result is regions experiencing high water scarcity leading to environmental degradation, conflicts and reduced industrial productivity. The aim of this paper was to quantify the water scarcity in the central and northern regions by calculating the water scarcity index—the ratio of annual water demand to availability. A focus of the paper was to determine the impact of the main industries in each region and investigate the benefit of implementing wáter reduction strategies within these industries. The water resources of each investigated region were found to be greatly overexploited and particularly so in the region of Antofagasta. The mining industry was found to be the greatest water consuming sector in this region and further analysis demonstrated that the degree of water scarcity could be greatly reduced by the implementation of water reduction strategies. The agricultural sector dominated water demand in all other regions and it was found that upgrading irrigation efficiency alongside reducing consumption in mining improved the situation in all regions. Nevertheless, given the scale of water scarcity, further investigation is necessary to obtain more recent and accurate data and analyze alternative strategies.