The effects of four intervals bf manual/hoeing compared to chemical/herbicides weeding were studi... more The effects of four intervals bf manual/hoeing compared to chemical/herbicides weeding were studied in coffee yield plantations for the 1959-1973 period. The treatments were: a) weeding intervals of 15, 30, 45 and 60 days; b) application of herbicides (three times per year). The results showed that there were no differences between manual and chemical weeding in coffee beans production. The procedure of the 45th day interval between weedings showed better effect on coffee yield and was the least expensive. The intense weed development between the 45th and 60th day interval between weedings increased the costs of the successive weeding. Higher P absorption by weed plants was found when the weeds reached the flowering and/or maturing stage of growth.
Farming Systems developed in Humid Tropical Zones are frequently characterized by a combination o... more Farming Systems developed in Humid Tropical Zones are frequently characterized by a combination of perennial and annual plants, intermixed in complex tree-crop associations. The productive functioning, the agronomic and economic performances, and the sustainability of these crop associations remain poorly understood. To improve the management capacity of these complex agroforestry systems, adequate indicators must be developed and integrated in assessment systems. These may then be used to aid farmers, assisted by their extension agents, in making decisions regarding management practices. The present study focused on the agroforestry systems developed by 38 farmers in the South West Region of Cameroon, which were surveyed for a large set of variables, aiming at formulating a Traditional Agroforestry Performance Indicators System (TAPIS). Analyses of the relationships among indicators in TAPIS allowed an improved understanding of agro-ecological and agro-economic performances in the studied plots, revealed tradeoffs regarding plant stand, income generation, food production, input demands and work requirements; and may contribute to the sustainability assessment of agroforestry systems.
The objective of this paper was to determine a method to allow the determination of good experime... more The objective of this paper was to determine a method to allow the determination of good experimental unit size, using the point of maximum curvature estimated, by algebraic calculus. There is an empiric relation between the coefficient of variation of experimental unit and its size. One example is presented and discussed to make possible the following conclusions: the method offers an algebraic solucion for the point of maximum curvature; the method does not permit different interpretations when the scale of the graph is dispossed differently; the method may present a size of experimental unit for high coefficient of variation, and in this case it is not recommended.
Due to global warming, there is a need to increase the water use efficiency of crops under rainfe... more Due to global warming, there is a need to increase the water use efficiency of crops under rainfed agriculture, particularly in semi-arid regions. Therefore, the effect of NPK fertilizer application (with or without liming) on the water use efficiency of a maize/cowpea intercropping system was investigated in the semi-arid part of Brazil. The crops were grown on a strongly acidic, sandy soil with three treatments: (i) Complete NPK fertilizer application with lime (Compl), (ii) Complete NPK fertilizer application without lime (Compl-L) and (iii) Control. On the average, dry matter production was 2.6 times higher with the Compl treatment than in the Control and 1.6 times higher than in the Compl-L treatment. The soil water balance was calculated with two different model approaches (HILLFLOW and EPICSEAR). When checked against measured soil water content during the growing period, both models produced accurate results, but only EPICSEAR was sensitive to the effects of liming and fertilizer application on soil water balance and dry matter production at this site. Comparison between the Compl and the Compl-L treatments shows that the increase in transpirational water use efficiency (WUET) (+63 and +80%, respectively) is mainly due to the application of NPK. Although the site is highly acid, liming was of minor importance for increasing the WUET. However, observations and simulations demonstrate that, through the additional application of lime, the gross water use efficiency (WUEC) in a maize/cowpea intercropping system can be increased by 60% compared to sole application of NPK and by more than 160% compared to the control. Abbreviations: EPIC – erosion productivity impact calculator; EPICSEAR – erosion productivity impact calculator for semi-arid regions; TDR – time domain reflectometry; WUE – water use efficiency.
Due to global warming, there is a need to increase the water use efficiency of crops under rainfe... more Due to global warming, there is a need to increase the water use efficiency of crops under rainfed agriculture, particularly in semi-arid regions. Therefore, the effect of NPK fertilizer application (with or without liming) on the water use efficiency of a maize/cowpea intercropping system was investigated in the semi-arid part of Brazil. The crops were grown on a strongly acidic, sandy soil with three treatments: (i) Complete NPK fertilizer application with lime (Compl), (ii) Complete NPK fertilizer application without lime (Compl-L) and (iii) Control. On the average, dry matter production was 2.6 times higher with the Compl treatment than in the Control and 1.6 times higher than in the Compl-L treatment. The soil water balance was calculated with two different model approaches (HILLFLOW and EPICSEAR). When checked against measured soil water content during the growing period, both models produced accurate results, but only EPICSEAR was sensitive to the effects of liming and fertilizer application on soil water balance and dry matter production at this site. Comparison between the Compl and the Compl-L treatments shows that the increase in transpirational water use efficiency (WUET) (+63 and +80%, respectively) is mainly due to the application of NPK. Although the site is highly acid, liming was of minor importance for increasing the WUET. However, observations and simulations demonstrate that, through the additional application of lime, the gross water use efficiency (WUEC) in a maize/cowpea intercropping system can be increased by 60% compared to sole application of NPK and by more than 160% compared to the control. Abbreviations: EPIC – erosion productivity impact calculator; EPICSEAR – erosion productivity impact calculator for semi-arid regions; TDR – time domain reflectometry; WUE – water use efficiency.
The effects of four intervals bf manual/hoeing compared to chemical/herbicides weeding were studi... more The effects of four intervals bf manual/hoeing compared to chemical/herbicides weeding were studied in coffee yield plantations for the 1959-1973 period. The treatments were: a) weeding intervals of 15, 30, 45 and 60 days; b) application of herbicides (three times per year). The results showed that there were no differences between manual and chemical weeding in coffee beans production. The procedure of the 45th day interval between weedings showed better effect on coffee yield and was the least expensive. The intense weed development between the 45th and 60th day interval between weedings increased the costs of the successive weeding. Higher P absorption by weed plants was found when the weeds reached the flowering and/or maturing stage of growth.
Farming Systems developed in Humid Tropical Zones are frequently characterized by a combination o... more Farming Systems developed in Humid Tropical Zones are frequently characterized by a combination of perennial and annual plants, intermixed in complex tree-crop associations. The productive functioning, the agronomic and economic performances, and the sustainability of these crop associations remain poorly understood. To improve the management capacity of these complex agroforestry systems, adequate indicators must be developed and integrated in assessment systems. These may then be used to aid farmers, assisted by their extension agents, in making decisions regarding management practices. The present study focused on the agroforestry systems developed by 38 farmers in the South West Region of Cameroon, which were surveyed for a large set of variables, aiming at formulating a Traditional Agroforestry Performance Indicators System (TAPIS). Analyses of the relationships among indicators in TAPIS allowed an improved understanding of agro-ecological and agro-economic performances in the studied plots, revealed tradeoffs regarding plant stand, income generation, food production, input demands and work requirements; and may contribute to the sustainability assessment of agroforestry systems.
The objective of this paper was to determine a method to allow the determination of good experime... more The objective of this paper was to determine a method to allow the determination of good experimental unit size, using the point of maximum curvature estimated, by algebraic calculus. There is an empiric relation between the coefficient of variation of experimental unit and its size. One example is presented and discussed to make possible the following conclusions: the method offers an algebraic solucion for the point of maximum curvature; the method does not permit different interpretations when the scale of the graph is dispossed differently; the method may present a size of experimental unit for high coefficient of variation, and in this case it is not recommended.
Due to global warming, there is a need to increase the water use efficiency of crops under rainfe... more Due to global warming, there is a need to increase the water use efficiency of crops under rainfed agriculture, particularly in semi-arid regions. Therefore, the effect of NPK fertilizer application (with or without liming) on the water use efficiency of a maize/cowpea intercropping system was investigated in the semi-arid part of Brazil. The crops were grown on a strongly acidic, sandy soil with three treatments: (i) Complete NPK fertilizer application with lime (Compl), (ii) Complete NPK fertilizer application without lime (Compl-L) and (iii) Control. On the average, dry matter production was 2.6 times higher with the Compl treatment than in the Control and 1.6 times higher than in the Compl-L treatment. The soil water balance was calculated with two different model approaches (HILLFLOW and EPICSEAR). When checked against measured soil water content during the growing period, both models produced accurate results, but only EPICSEAR was sensitive to the effects of liming and fertilizer application on soil water balance and dry matter production at this site. Comparison between the Compl and the Compl-L treatments shows that the increase in transpirational water use efficiency (WUET) (+63 and +80%, respectively) is mainly due to the application of NPK. Although the site is highly acid, liming was of minor importance for increasing the WUET. However, observations and simulations demonstrate that, through the additional application of lime, the gross water use efficiency (WUEC) in a maize/cowpea intercropping system can be increased by 60% compared to sole application of NPK and by more than 160% compared to the control. Abbreviations: EPIC – erosion productivity impact calculator; EPICSEAR – erosion productivity impact calculator for semi-arid regions; TDR – time domain reflectometry; WUE – water use efficiency.
Due to global warming, there is a need to increase the water use efficiency of crops under rainfe... more Due to global warming, there is a need to increase the water use efficiency of crops under rainfed agriculture, particularly in semi-arid regions. Therefore, the effect of NPK fertilizer application (with or without liming) on the water use efficiency of a maize/cowpea intercropping system was investigated in the semi-arid part of Brazil. The crops were grown on a strongly acidic, sandy soil with three treatments: (i) Complete NPK fertilizer application with lime (Compl), (ii) Complete NPK fertilizer application without lime (Compl-L) and (iii) Control. On the average, dry matter production was 2.6 times higher with the Compl treatment than in the Control and 1.6 times higher than in the Compl-L treatment. The soil water balance was calculated with two different model approaches (HILLFLOW and EPICSEAR). When checked against measured soil water content during the growing period, both models produced accurate results, but only EPICSEAR was sensitive to the effects of liming and fertilizer application on soil water balance and dry matter production at this site. Comparison between the Compl and the Compl-L treatments shows that the increase in transpirational water use efficiency (WUET) (+63 and +80%, respectively) is mainly due to the application of NPK. Although the site is highly acid, liming was of minor importance for increasing the WUET. However, observations and simulations demonstrate that, through the additional application of lime, the gross water use efficiency (WUEC) in a maize/cowpea intercropping system can be increased by 60% compared to sole application of NPK and by more than 160% compared to the control. Abbreviations: EPIC – erosion productivity impact calculator; EPICSEAR – erosion productivity impact calculator for semi-arid regions; TDR – time domain reflectometry; WUE – water use efficiency.
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