ABSTRACT Irrigation scheduling is critically important to avoid the loss of water, fuel and chemi... more ABSTRACT Irrigation scheduling is critically important to avoid the loss of water, fuel and chemicals by over application of water, or a reduction in crop yield if too little water is applied. In this paper a web-based irrigation scheduling approach is described. The approach is based on applying irrigation water at the rate of the estimated potential evapotranspiration, which is equivalent to the crop water requirement. Reference evapotranspiration is obtained from an operational water and energy balance algorithm (GOES-PREWEB) which produces a suite of hydro-climate variables on a daily basis for Puerto Rico. The algorithm produces daily estimates of the Penman-Monteith, Priestly-Taylor and Hargreaves-Samani reference evapotranspiration. The crop coefficient curve is constructed per the methodology recommended by the United Nations Food and Agriculture Organization (FAO). Daily rainfall can be obtained from radar (NEXRAD) if rain gauge data is not available for the farm. A detailed example is provided for a farm growing tomato in Juana Diaz, PR. The approach is relatively simple and the near-real time data is available to any farmer in Puerto Rico with internet access.
A study was conducted to evaluate the influence of agricultural lime (CaCOî) on the movement and ... more A study was conducted to evaluate the influence of agricultural lime (CaCOî) on the movement and uptake of inorganic nitrogen for a sweet pepper crop (Capsicum annuum) grown on an Oxisol soil (Coto clay) in northwest Puerto Rico. The Coto clay soil, which contains the 1:1 kaolinite mineral, has a low pH (4 to 4.5). The 1:1 type clays are known to possess a net positive charge at low pH, resulting in the adsorption of negatively charged ions such as nitrate. From an environmental standpoint this characteristic of the 1:1 clay is favorable, since nitrate leaching, a major cause of groundwater pollution in many areas, is reduced relative to soils with net negative charge. However, agricultural plants, such as sweet peppers, favor a higher soil pH (approximately 6.5), which can be obtained by the application of agricultural lime. This application, however, may have the negative effect of increasing the potential for nitrate leaching, as the net charge in the soil particles becomes posit...
Stomatal resistance (rL), surface resistance (rs) and leaf temperature (TL) are important physiol... more Stomatal resistance (rL), surface resistance (rs) and leaf temperature (TL) are important physiological variables for the understanding of the interaction between the soil, plant, and atmosphere. These variables are used to study the response of plants to abiotic stress conditions, such as drought and high temperature, in addition to micrometeorological variables such as evapotranspiration (ET). The goal of this research was to measure the rL, rs and TL of four genotypes of common bean (Phaseolus vulgaris L.) under drought and non-drought conditions in a greenhouse environment. Three drought-tolerant genotypes were studied, BAT 477, SER 16 and SER 21, and one drought susceptible genotype, Morales. Three water regimes were used: full water supply (FWS) using 80% of the water required for soil saturation (WS) during the complete growing season; Stress 1 (S1) with 50% of WS before flowering and 60% of WS after flowering; and Stress 2 (S2) with 20% of WS before flowering and 40% of WS a...
Journal of Applied Meteorology and Climatology, 2017
Hourly data collected from ground stations were used to study the maximum daytime heat index Hi i... more Hourly data collected from ground stations were used to study the maximum daytime heat index Hi in the Mesoamerica and Caribbean Sea (MAC) region for a 35-yr period (1980–2014). Observations of Hi revealed larger values during the rainy season and smaller values during the dry season. The Hi climatology exhibits the largest values in Mesoamerica, followed by the Greater Antilles and then by the Lesser Antilles. The trend in Hi indicates a notable increasing pattern of 0.05°C yr−1 (0.10°F yr−1), and the trends are more prominent in Mesoamerica than in Caribbean countries. This work also includes the analysis of heat index extreme events (HIEE). Usually the extreme values of the heat index are used for advising heat warning events, and it was found that 45 HIEEs occurred during the studied period. The average duration of HIEE was 2.4 days, and the average relative intensity (excess over the threshold) was 2.4°C (4.3°F). It was found that 82% of HIEE lasted 2 or 2.5 days and 80% exhibi...
Nitrate leaching through the soil profile can result in a significant loss of fertilizer N, and m... more Nitrate leaching through the soil profile can result in a significant loss of fertilizer N, and may be a source of nitrate concentration in groundwater. Highly weathered soils may exhibit substantial anion exchange capacity (AEC), which retards the movement of anions such as NO3" through the profile. However, AEC decreases as soil pH increases with agronomic practices such as liming. A study was conducted to determine the effect of lime application and frequency of Ν fertigation on NH4+ and NO3" concentrations on Coto clay. A field experiment was established at the UPR Experiment Station at Isabela, PR, using peppers as the test crop. Two lime treatments (lime or no lime) and two fertigation frequencies (weekly or bi-weekly applications) were evaluated. Soil samples were collected every two weeks at four depths and analyzed for NH4+ and NO3" by steam distillation. During the first year, probably due to spatial variabil ity and buffering capacity of the Coto clay, the ...
Abstract:- Rain gauge networks are used to calibrate and validate quantitative precipitation esti... more Abstract:- Rain gauge networks are used to calibrate and validate quantitative precipitation estimation (QPE) methods based on remote sensing, which may be used as data sources for hydrologic models. The typical approach is to adjust (calibrate) or compare (validate) the rainfall in the QPE pixel with the rain gauge located within the pixel. The QPE result represents a mean rainfall over the pixel area, whereas the rainfall from the gauge represents a point, although it is normally assumed to represent some area. In most cases the QPE pixel area is millions of square meter in size. We hypothesize that some rain gauge networks in environments similar to this study (i.e., tropical coastal), which provide only one rain gauge per remote sensing pixel, may lead to error when used to calibrate/validate QPE methods, and that consequently these errors may be propagated throughout hydrologic models. The objective of this paper is to describe a ground-truth rain gauge network located in weste...
ABSTRACT Irrigation scheduling is critically important to avoid the loss of water, fuel and chemi... more ABSTRACT Irrigation scheduling is critically important to avoid the loss of water, fuel and chemicals by over application of water, or a reduction in crop yield if too little water is applied. In this paper a web-based irrigation scheduling approach is described. The approach is based on applying irrigation water at the rate of the estimated potential evapotranspiration, which is equivalent to the crop water requirement. Reference evapotranspiration is obtained from an operational water and energy balance algorithm (GOES-PREWEB) which produces a suite of hydro-climate variables on a daily basis for Puerto Rico. The algorithm produces daily estimates of the Penman-Monteith, Priestly-Taylor and Hargreaves-Samani reference evapotranspiration. The crop coefficient curve is constructed per the methodology recommended by the United Nations Food and Agriculture Organization (FAO). Daily rainfall can be obtained from radar (NEXRAD) if rain gauge data is not available for the farm. A detailed example is provided for a farm growing tomato in Juana Diaz, PR. The approach is relatively simple and the near-real time data is available to any farmer in Puerto Rico with internet access.
A study was conducted to evaluate the influence of agricultural lime (CaCOî) on the movement and ... more A study was conducted to evaluate the influence of agricultural lime (CaCOî) on the movement and uptake of inorganic nitrogen for a sweet pepper crop (Capsicum annuum) grown on an Oxisol soil (Coto clay) in northwest Puerto Rico. The Coto clay soil, which contains the 1:1 kaolinite mineral, has a low pH (4 to 4.5). The 1:1 type clays are known to possess a net positive charge at low pH, resulting in the adsorption of negatively charged ions such as nitrate. From an environmental standpoint this characteristic of the 1:1 clay is favorable, since nitrate leaching, a major cause of groundwater pollution in many areas, is reduced relative to soils with net negative charge. However, agricultural plants, such as sweet peppers, favor a higher soil pH (approximately 6.5), which can be obtained by the application of agricultural lime. This application, however, may have the negative effect of increasing the potential for nitrate leaching, as the net charge in the soil particles becomes posit...
Stomatal resistance (rL), surface resistance (rs) and leaf temperature (TL) are important physiol... more Stomatal resistance (rL), surface resistance (rs) and leaf temperature (TL) are important physiological variables for the understanding of the interaction between the soil, plant, and atmosphere. These variables are used to study the response of plants to abiotic stress conditions, such as drought and high temperature, in addition to micrometeorological variables such as evapotranspiration (ET). The goal of this research was to measure the rL, rs and TL of four genotypes of common bean (Phaseolus vulgaris L.) under drought and non-drought conditions in a greenhouse environment. Three drought-tolerant genotypes were studied, BAT 477, SER 16 and SER 21, and one drought susceptible genotype, Morales. Three water regimes were used: full water supply (FWS) using 80% of the water required for soil saturation (WS) during the complete growing season; Stress 1 (S1) with 50% of WS before flowering and 60% of WS after flowering; and Stress 2 (S2) with 20% of WS before flowering and 40% of WS a...
Journal of Applied Meteorology and Climatology, 2017
Hourly data collected from ground stations were used to study the maximum daytime heat index Hi i... more Hourly data collected from ground stations were used to study the maximum daytime heat index Hi in the Mesoamerica and Caribbean Sea (MAC) region for a 35-yr period (1980–2014). Observations of Hi revealed larger values during the rainy season and smaller values during the dry season. The Hi climatology exhibits the largest values in Mesoamerica, followed by the Greater Antilles and then by the Lesser Antilles. The trend in Hi indicates a notable increasing pattern of 0.05°C yr−1 (0.10°F yr−1), and the trends are more prominent in Mesoamerica than in Caribbean countries. This work also includes the analysis of heat index extreme events (HIEE). Usually the extreme values of the heat index are used for advising heat warning events, and it was found that 45 HIEEs occurred during the studied period. The average duration of HIEE was 2.4 days, and the average relative intensity (excess over the threshold) was 2.4°C (4.3°F). It was found that 82% of HIEE lasted 2 or 2.5 days and 80% exhibi...
Nitrate leaching through the soil profile can result in a significant loss of fertilizer N, and m... more Nitrate leaching through the soil profile can result in a significant loss of fertilizer N, and may be a source of nitrate concentration in groundwater. Highly weathered soils may exhibit substantial anion exchange capacity (AEC), which retards the movement of anions such as NO3" through the profile. However, AEC decreases as soil pH increases with agronomic practices such as liming. A study was conducted to determine the effect of lime application and frequency of Ν fertigation on NH4+ and NO3" concentrations on Coto clay. A field experiment was established at the UPR Experiment Station at Isabela, PR, using peppers as the test crop. Two lime treatments (lime or no lime) and two fertigation frequencies (weekly or bi-weekly applications) were evaluated. Soil samples were collected every two weeks at four depths and analyzed for NH4+ and NO3" by steam distillation. During the first year, probably due to spatial variabil ity and buffering capacity of the Coto clay, the ...
Abstract:- Rain gauge networks are used to calibrate and validate quantitative precipitation esti... more Abstract:- Rain gauge networks are used to calibrate and validate quantitative precipitation estimation (QPE) methods based on remote sensing, which may be used as data sources for hydrologic models. The typical approach is to adjust (calibrate) or compare (validate) the rainfall in the QPE pixel with the rain gauge located within the pixel. The QPE result represents a mean rainfall over the pixel area, whereas the rainfall from the gauge represents a point, although it is normally assumed to represent some area. In most cases the QPE pixel area is millions of square meter in size. We hypothesize that some rain gauge networks in environments similar to this study (i.e., tropical coastal), which provide only one rain gauge per remote sensing pixel, may lead to error when used to calibrate/validate QPE methods, and that consequently these errors may be propagated throughout hydrologic models. The objective of this paper is to describe a ground-truth rain gauge network located in weste...
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