The sorption of organic compounds to soil is mainly through organic matter components. The organi... more The sorption of organic compounds to soil is mainly through organic matter components. The organic matter amount and type depends on soil properties such as pH, conductivity, particle size and calcium carbonate content. Therefore, organic pesticide movement-through soil strongly depends on the genesis of organic matter. Organic matter has fractions such as humic acid (HA) and fluvic acid (FA), fats and oils. For this study three tropical soils were chosen, Aguilita, Catano and Tiburones. Some of their organic matter properties, such as total acidity, UV-Vis and IR spectra were related to the sorption coefficient (Koc) of carbofuran and metolachlor. Sorption coefficients in Aguilita, Catano and Tiburones were between 34 and 1,181 ml/g for carbofuran and between 90 and 298 ml/g for metolachlor. Solutions of 100 ug/ml HAs from Aguilita, Catano, and Tiburones dissolved in 0.05N NaHC03 of pH 8.1 had E4/E6 absorption values of 5.5, 4.9 and 3.2, respectively; and those from FA in 2N HCl had values of 10.0, 6.5 and 10.4, respectively. These values suggest a highly aromatic content for HA from Tiburones (E4/E6 ~3) and mainly aliphatic for Aguilita soil. Fulvic acids from Aguilita and Tiburones soils had highly aliphatic character (E4/E6 > 8) whereas that of Catano was intermediate. Data suggest that differences in metolachlor and carbofuran Koc values for the above mentioned soils are mainly due to differences in HA and FA properties of the soils.
A field experiment was conducted to determine the economic feasibility of intercrop- ping bean (P... more A field experiment was conducted to determine the economic feasibility of intercrop- ping bean (Phaseolus vulgaris L.) and plantain (Musa acuminata χ M· balbisiana AAB) at Corozal, Puerto Rico in 1995-1996. Treatment variables consisted of two bean cultivars (Arroyo Loro and 9443-1) and two frequencies of intercroppings (once and twice). The results indicated that two intercroppings of 9443-1 outyielded significantly (P<0.05) one intercropping of Arroyo Loro but did not outyield one intercropping of 9443-1. However, there was no significant yield difference between the two intercroppings of Arroyo Loro and the two intercroppings of 9443-1. Plantain yield, in terms of the number of fruits, was not significantly affected by intercropping. The highest net income of the intercropping treatment was obtained from the two intercroppings of 9443-1 ($7,706/ha). This represents an additional income of $ 4,922/ha over that of plantain monoculture. The high production cost of bean incurred from two intercroppings resulted in less-than- expected net income as compared to that of one intercropping within one growing cycle of plantain.
The Journal of Agriculture of the University of Puerto Rico, 1969
Five commercial greenhouses in the central mountainous zone of Puerto Rico were studied in order ... more Five commercial greenhouses in the central mountainous zone of Puerto Rico were studied in order to identify changes in soil factors that affect P retention. Soils were collected both within and outside drainages at a 0- to 15-cm depth. Soil physicochemical properties varied in samples taken both within and outside drainages. The high Fe and Al content in the soils of this study suggested a high phosphorus retention capacity. Laboratory estimates of P retention parameters indicated differences in P sorption capacity among soils. Phosphorus retention parameters were highly correlated with citrate dithionite extractable Fe. The equilibrium P concentration was also correlated with citrate dithionate Al in soils outside drainages. This finding was due to the higher soil organic matter counterbalancing the soil P retention capability of Al, all of which indicates the importance of clearing all drainages of organic residues in order to avoid excessive movement of P outside the greenhouse ...
Improvement of selection criteria for breeding sweet potato in terms of flavor would be greatly f... more Improvement of selection criteria for breeding sweet potato in terms of flavor would be greatly facilitated by understanding its volatile composition. The aroma in the sweet potato comes from volatile compounds released by biochemical synthesis and chemical transformations during cooking. For ascertaining the chemical composition of the aroma, samples were baked in a closed system coupled to a cold solvent trap having dichloromethane. Aroma constituents were subsequently identified and quantified by using a gas Chromatograph coupled to a quadruple mass spectrometer. Amounts of volatiles were compared with the flesh's physical properties and sugar content. Results suggest a straight relationship among some volatiles between them and in between some physical and chemical properties such as starch granule size and sugar content.
The Journal of Agriculture of the University of Puerto Rico, 1969
Dissipation rate of prometryn, oxyfluorfen and imazethapyr was estimated in the Mollisol San Antó... more Dissipation rate of prometryn, oxyfluorfen and imazethapyr was estimated in the Mollisol San Antón and the Vertisol Fraternidad soil series, both soils from the south semi-arid coastal region of Puerto Rico. The study was carried out in two consecutive years. The herbicides were applied one day after seeding pigeon peas at Juana Díaz (San Antón soil series) and Lajas (Fraternidad soil series) Agricultural Experiment Substations. Herbicide rates were 2.24, 0.28 and 0.070 kg ai/ha for prometryn, oxyfluorfen and imazethapyr, respectively. Soil samples at 15-cm depth were collected at 0, 28, 56,112 and 168 days after application. Field half-lives between 2 and 43, 31 and 88, and 19 and 46 days were found for prometryn, oxyfluorfen and imazethapyr, respectively. Substantial dissipation rate variability for above mentioned herbicides has been shown to occur within the soil and year treatments. These findings suggest very short and variable persistence for the three herbicides in both soil...
Pesticide sorption in soil involves many factors, such as pH, soil redox, the amount and type of ... more Pesticide sorption in soil involves many factors, such as pH, soil redox, the amount and type of humic acids (organic matter), clays and metallic species. Little work in carbonatic soils has been done to study the effect of the above mentioned factors on the sorption of pesticides. Studies were conducted to determine the interaction between these factors and the carbonatic soils. Twelve carbonatic soil series and nine non-carbonatic soil series showed that redox properties for carbonatic soils tended to be smaller and, contrary to the non-carbonatic soils, many of them with negative potentials. We observed a positive correlation between water extractable iron versus diluted acid extractable iron for the carbonatic soils (R2 = 0.88) but not for the non-carbonatic soils. This finding suggests that the reductive environment of carbonatic soils favors the ferrous species (Fe+2) rather than the ferric (Fe+3). These factors apparently affect the solubility of the organic matter, thus decr...
The Journal of Agriculture of the University of Puerto Rico, 1969
For fresh market sweet potato [Ipomea batatas (L.) Lam] quality is defined in terms of attractive... more For fresh market sweet potato [Ipomea batatas (L.) Lam] quality is defined in terms of attractiveness, sweetness, texture, and flavor composed of taste and odor after cooking. There is a scarcity of information regarding taste and volátiles of tropical type sweet potatoes. The first objective of this research was to provide a robust set of data for carbohydrate type and levels, alcohol insoluble solids (AIS) and volatile organic compounds (VOC) from six cultivars of sweet potato, data which will allow us to have a quantitative selection tool besides crop yield, tuber size and appearance. The second objective was to relate VOC differences among sweet potato cultivars that can be attributed to chemical and physical differences of the pulp before and after cooking. A three- harvest study was conducted to identify and determine major carbohydrate content, AIS, starch granule diameter and form, and tastes and odors of six cultivars of sweet potato, which were very sweet ('Gem'), ...
The Journal of Agriculture of the University of Puerto Rico, 2012
The distribution and chemical properties of humic substances (humic acids and fulvic acids) from ... more The distribution and chemical properties of humic substances (humic acids and fulvic acids) from a twelve-month-old static aerated compost pile of coffee pulp were studied. The compost was separated into five physical granule fractions (500, 1000, 2000, 4000 and 8000 um) in order to determine the effect of particle size on humic substances, on nutrient composition, and on distribution. The objective of this study was to understand the chemical properties and distribution of humic substances in mature coffee pulp compost. There were no significant differences across fractions for total N and available P2O5; these fractions averaged 4.9 and 0.66%, respectively. Potassium (K) increased as fraction size increased, from 3.01 to 3.94%. Readily available nitrogen, NO3 and NH4, was 7.19% of the total N. Eighty-nine percent of the total K was exchangeable K ions, and these varied within compost fractions from 2.82 to 3.33%. Approximately 50% of the total Ca and Mg were exchangeable ions; Ca ...
The sorption of organic compounds to soil is mainly through organic matter components. The organi... more The sorption of organic compounds to soil is mainly through organic matter components. The organic matter amount and type depends on soil properties such as pH, conductivity, particle size and calcium carbonate content. Therefore, organic pesticide movement-through soil strongly depends on the genesis of organic matter. Organic matter has fractions such as humic acid (HA) and fluvic acid (FA), fats and oils. For this study three tropical soils were chosen, Aguilita, Catano and Tiburones. Some of their organic matter properties, such as total acidity, UV-Vis and IR spectra were related to the sorption coefficient (Koc) of carbofuran and metolachlor. Sorption coefficients in Aguilita, Catano and Tiburones were between 34 and 1,181 ml/g for carbofuran and between 90 and 298 ml/g for metolachlor. Solutions of 100 ug/ml HAs from Aguilita, Catano, and Tiburones dissolved in 0.05N NaHC03 of pH 8.1 had E4/E6 absorption values of 5.5, 4.9 and 3.2, respectively; and those from FA in 2N HCl had values of 10.0, 6.5 and 10.4, respectively. These values suggest a highly aromatic content for HA from Tiburones (E4/E6 ~3) and mainly aliphatic for Aguilita soil. Fulvic acids from Aguilita and Tiburones soils had highly aliphatic character (E4/E6 > 8) whereas that of Catano was intermediate. Data suggest that differences in metolachlor and carbofuran Koc values for the above mentioned soils are mainly due to differences in HA and FA properties of the soils.
A field experiment was conducted to determine the economic feasibility of intercrop- ping bean (P... more A field experiment was conducted to determine the economic feasibility of intercrop- ping bean (Phaseolus vulgaris L.) and plantain (Musa acuminata χ M· balbisiana AAB) at Corozal, Puerto Rico in 1995-1996. Treatment variables consisted of two bean cultivars (Arroyo Loro and 9443-1) and two frequencies of intercroppings (once and twice). The results indicated that two intercroppings of 9443-1 outyielded significantly (P<0.05) one intercropping of Arroyo Loro but did not outyield one intercropping of 9443-1. However, there was no significant yield difference between the two intercroppings of Arroyo Loro and the two intercroppings of 9443-1. Plantain yield, in terms of the number of fruits, was not significantly affected by intercropping. The highest net income of the intercropping treatment was obtained from the two intercroppings of 9443-1 ($7,706/ha). This represents an additional income of $ 4,922/ha over that of plantain monoculture. The high production cost of bean incurred from two intercroppings resulted in less-than- expected net income as compared to that of one intercropping within one growing cycle of plantain.
The Journal of Agriculture of the University of Puerto Rico, 1969
Five commercial greenhouses in the central mountainous zone of Puerto Rico were studied in order ... more Five commercial greenhouses in the central mountainous zone of Puerto Rico were studied in order to identify changes in soil factors that affect P retention. Soils were collected both within and outside drainages at a 0- to 15-cm depth. Soil physicochemical properties varied in samples taken both within and outside drainages. The high Fe and Al content in the soils of this study suggested a high phosphorus retention capacity. Laboratory estimates of P retention parameters indicated differences in P sorption capacity among soils. Phosphorus retention parameters were highly correlated with citrate dithionite extractable Fe. The equilibrium P concentration was also correlated with citrate dithionate Al in soils outside drainages. This finding was due to the higher soil organic matter counterbalancing the soil P retention capability of Al, all of which indicates the importance of clearing all drainages of organic residues in order to avoid excessive movement of P outside the greenhouse ...
Improvement of selection criteria for breeding sweet potato in terms of flavor would be greatly f... more Improvement of selection criteria for breeding sweet potato in terms of flavor would be greatly facilitated by understanding its volatile composition. The aroma in the sweet potato comes from volatile compounds released by biochemical synthesis and chemical transformations during cooking. For ascertaining the chemical composition of the aroma, samples were baked in a closed system coupled to a cold solvent trap having dichloromethane. Aroma constituents were subsequently identified and quantified by using a gas Chromatograph coupled to a quadruple mass spectrometer. Amounts of volatiles were compared with the flesh's physical properties and sugar content. Results suggest a straight relationship among some volatiles between them and in between some physical and chemical properties such as starch granule size and sugar content.
The Journal of Agriculture of the University of Puerto Rico, 1969
Dissipation rate of prometryn, oxyfluorfen and imazethapyr was estimated in the Mollisol San Antó... more Dissipation rate of prometryn, oxyfluorfen and imazethapyr was estimated in the Mollisol San Antón and the Vertisol Fraternidad soil series, both soils from the south semi-arid coastal region of Puerto Rico. The study was carried out in two consecutive years. The herbicides were applied one day after seeding pigeon peas at Juana Díaz (San Antón soil series) and Lajas (Fraternidad soil series) Agricultural Experiment Substations. Herbicide rates were 2.24, 0.28 and 0.070 kg ai/ha for prometryn, oxyfluorfen and imazethapyr, respectively. Soil samples at 15-cm depth were collected at 0, 28, 56,112 and 168 days after application. Field half-lives between 2 and 43, 31 and 88, and 19 and 46 days were found for prometryn, oxyfluorfen and imazethapyr, respectively. Substantial dissipation rate variability for above mentioned herbicides has been shown to occur within the soil and year treatments. These findings suggest very short and variable persistence for the three herbicides in both soil...
Pesticide sorption in soil involves many factors, such as pH, soil redox, the amount and type of ... more Pesticide sorption in soil involves many factors, such as pH, soil redox, the amount and type of humic acids (organic matter), clays and metallic species. Little work in carbonatic soils has been done to study the effect of the above mentioned factors on the sorption of pesticides. Studies were conducted to determine the interaction between these factors and the carbonatic soils. Twelve carbonatic soil series and nine non-carbonatic soil series showed that redox properties for carbonatic soils tended to be smaller and, contrary to the non-carbonatic soils, many of them with negative potentials. We observed a positive correlation between water extractable iron versus diluted acid extractable iron for the carbonatic soils (R2 = 0.88) but not for the non-carbonatic soils. This finding suggests that the reductive environment of carbonatic soils favors the ferrous species (Fe+2) rather than the ferric (Fe+3). These factors apparently affect the solubility of the organic matter, thus decr...
The Journal of Agriculture of the University of Puerto Rico, 1969
For fresh market sweet potato [Ipomea batatas (L.) Lam] quality is defined in terms of attractive... more For fresh market sweet potato [Ipomea batatas (L.) Lam] quality is defined in terms of attractiveness, sweetness, texture, and flavor composed of taste and odor after cooking. There is a scarcity of information regarding taste and volátiles of tropical type sweet potatoes. The first objective of this research was to provide a robust set of data for carbohydrate type and levels, alcohol insoluble solids (AIS) and volatile organic compounds (VOC) from six cultivars of sweet potato, data which will allow us to have a quantitative selection tool besides crop yield, tuber size and appearance. The second objective was to relate VOC differences among sweet potato cultivars that can be attributed to chemical and physical differences of the pulp before and after cooking. A three- harvest study was conducted to identify and determine major carbohydrate content, AIS, starch granule diameter and form, and tastes and odors of six cultivars of sweet potato, which were very sweet ('Gem'), ...
The Journal of Agriculture of the University of Puerto Rico, 2012
The distribution and chemical properties of humic substances (humic acids and fulvic acids) from ... more The distribution and chemical properties of humic substances (humic acids and fulvic acids) from a twelve-month-old static aerated compost pile of coffee pulp were studied. The compost was separated into five physical granule fractions (500, 1000, 2000, 4000 and 8000 um) in order to determine the effect of particle size on humic substances, on nutrient composition, and on distribution. The objective of this study was to understand the chemical properties and distribution of humic substances in mature coffee pulp compost. There were no significant differences across fractions for total N and available P2O5; these fractions averaged 4.9 and 0.66%, respectively. Potassium (K) increased as fraction size increased, from 3.01 to 3.94%. Readily available nitrogen, NO3 and NH4, was 7.19% of the total N. Eighty-nine percent of the total K was exchangeable K ions, and these varied within compost fractions from 2.82 to 3.33%. Approximately 50% of the total Ca and Mg were exchangeable ions; Ca ...
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