In East Africa where a drastic improvement in food security is an urgent need, rice, a non-traditional crop in most of countries in the region, has emerged as an important food crop that could extend the Green Revolut...In East Africa where a drastic improvement in food security is an urgent need, rice, a non-traditional crop in most of countries in the region, has emerged as an important food crop that could extend the Green Revolution to the region following the introduction of New Rice for Africa (NERICA) in the early 2000s. Using data collected through a nationwide survey, this paper examines the possibility of rice green revolution by estimating the technical efficiency (TE) of rainfed rice farmers in Uganda and simulates how unfavorable climate changes affect it. The estimated stochastic frontier yield function showed that the mean TE was 65% for lowland and 60% for upland, and that the potential yield of rainfed rice cultivation was as high as 3 t·ha-1. However, the stochastic simulation of rainfall and rice yield revealed that unfavorable climate changes could erase the high potential in crop yield. Rainfed rice cultivation could be a leading sector for realizing Green Revolution in East Africa. It plays a critical role in this process to improve rice farmers’ TE, which is lower in the region than in Asia. Worsening climatic conditions, if occur, make this need even more imperative.展开更多
Monochromatic light-emitting diode lamps (LEDs), emitting red and blue lights, revolutionized crop production in closed-system plant factories with artificial lighting in the early 1990s. The LED industry developed br...Monochromatic light-emitting diode lamps (LEDs), emitting red and blue lights, revolutionized crop production in closed-system plant factories with artificial lighting in the early 1990s. The LED industry developed broad-spectrum white-LEDs by 2010, and many types of white-LEDs for home and office uses are now available for plant factory entrepreneurs. This paper tries to clarify whether these white-LEDs can be used as effective light sources in plant factories by examining what types of spectrum distribution are better suited for plant production. An experiment was conducted using seven LEDs, of which six were white-LEDs, to compare the performance in producing lettuce, and the results were compared with recent studies that used white-LEDs for growing lettuce under closed-system production conditions. Results showed that broad-spectrum white-LEDs performed significantly better than narrow-spectrum LEDs. Among lights in conventional color bands, red and blue lights give critical effects on plant growth, not in isolation but in combination;not too “cool” white LEDs perform better. Green and far-red lights also have some positive effects. Altogether, for a given light intensity, broad-spectrum white LEDs outperform narrow-spectrum LEDs. It is found that the spectrum distribution for white-LEDs to attain high productivity in lettuce production is such that the percentage share of photon flux density by conventional color band falls in the following ranges: 0% < blue < 30%, 0% < green < 50%, 30% < red < 70%, and 0% < far-red < 20%.展开更多
文摘In East Africa where a drastic improvement in food security is an urgent need, rice, a non-traditional crop in most of countries in the region, has emerged as an important food crop that could extend the Green Revolution to the region following the introduction of New Rice for Africa (NERICA) in the early 2000s. Using data collected through a nationwide survey, this paper examines the possibility of rice green revolution by estimating the technical efficiency (TE) of rainfed rice farmers in Uganda and simulates how unfavorable climate changes affect it. The estimated stochastic frontier yield function showed that the mean TE was 65% for lowland and 60% for upland, and that the potential yield of rainfed rice cultivation was as high as 3 t·ha-1. However, the stochastic simulation of rainfall and rice yield revealed that unfavorable climate changes could erase the high potential in crop yield. Rainfed rice cultivation could be a leading sector for realizing Green Revolution in East Africa. It plays a critical role in this process to improve rice farmers’ TE, which is lower in the region than in Asia. Worsening climatic conditions, if occur, make this need even more imperative.
文摘Monochromatic light-emitting diode lamps (LEDs), emitting red and blue lights, revolutionized crop production in closed-system plant factories with artificial lighting in the early 1990s. The LED industry developed broad-spectrum white-LEDs by 2010, and many types of white-LEDs for home and office uses are now available for plant factory entrepreneurs. This paper tries to clarify whether these white-LEDs can be used as effective light sources in plant factories by examining what types of spectrum distribution are better suited for plant production. An experiment was conducted using seven LEDs, of which six were white-LEDs, to compare the performance in producing lettuce, and the results were compared with recent studies that used white-LEDs for growing lettuce under closed-system production conditions. Results showed that broad-spectrum white-LEDs performed significantly better than narrow-spectrum LEDs. Among lights in conventional color bands, red and blue lights give critical effects on plant growth, not in isolation but in combination;not too “cool” white LEDs perform better. Green and far-red lights also have some positive effects. Altogether, for a given light intensity, broad-spectrum white LEDs outperform narrow-spectrum LEDs. It is found that the spectrum distribution for white-LEDs to attain high productivity in lettuce production is such that the percentage share of photon flux density by conventional color band falls in the following ranges: 0% < blue < 30%, 0% < green < 50%, 30% < red < 70%, and 0% < far-red < 20%.
