No abstract

No abstract

Intercropping is presently a major method of crop production in tropical Africa, subtropical Asia, and Central and South America. With this approach, crops are planted in such a variety of combinations that the merits of intercropping as compared with monoculture are often difficult to determine. Our objective was to evaluate the merits of intercropping legumes and grasses in the United States. Corn (Zea mays L.) was intercropped with cowpea (Vigna unguiculata (L.) Walp.] and soybean [Glycine max (L.) Merr.] on a Norfolk sandy loam soil (fine, loamy siliceous, thermic Typic Paleudult). The legumes were either planted in the rows with corn or alternate to the corn rows. Control plots were monocrops of corn and the legumes, with each species fertilized according to soil test recommendations. Both dry matter and seed yield of the monocrops were higher than the individual components in the intercrops. Intercropped corn yield ranged from 46 to 90% of the reference monoculture. The lower dry matter production in the intercropped plots may have been due to competition between the corn and legume components for N. Seed yield of intercropped cowpea ranged from 42 to 56% of monoculture. Intercropped soybean seed yield ranged from 52 to 54% in 1980, and 48 to 60% in 1981 of the monoculture. Dry matter accumulation was significantly greater for the monocrops but varied non‐significantly, between the alternate and within row system. The corn‐cowpea intercrops, which had Land Equivalent Ratios (LER) up to 1.27 in 1980 and 1.32 in 1981 and Area Time Equivalent Ratios (ATER) as high as 1.19 in 1980 and 1.25 in 1981, were more productive than the corn‐soybean intercrops. The corn‐soybean combination had a maximum LER in 1980 of 1.22 and 1.10 in 1981, while the maximum ATER was 1.12 in 1980 and 1.01 in 1981. Thus, both the LER and ATER showed that intercropping resulted in greater productivity per unit of land than monocultures of the intercrop components.

Particulate and gaseous emissions from indoor combustion appliances and smoking can elevate the indoor concentrations of various pollutants.Indoor pollutant concentrations resulting from operating one of several combustion appliances, or from sidestream tobacco smoke, were measured in a 27-m 3 environmental chamber under varying ventilation rates. 7he combustion appliances investigated were gas-fired cooking stoves, unvented kerosene-fired space heaters, and unvented natural gas-fired space heaters. Results showed elevated levels of carbon dioxide, carbon monoxide, nitric oxide, nitrogen dioxide, formaldehyde, and suspended particles from one or more of the pollutant sources investigated. Our findings suggest that, of the sources examined in this study, nitrogen dioxide from combustion appliances and particles from sidestream cigarette smoke are the most serious contaminants of indoor air, if we use existing standards and guidelines as the criteria. An emission rate model was used to quantify the strengths of the pollutant sources, which are reported in terms of the mass of pollutant emitted per energy unit of fuel consumed (in the case of gas and kerosene appliances) and per mass of tobacco combusted (in the case of smoking). IUTRODUCTIOUIndoor combustion appliances and tobacco smoking are primary sources of air pollution in many residences. Gas-fired stoves and unvented space heaters (both kerosene-and natural gas-fired types) emit such potentially harmful pollutants as carbon monoxide (CO), carbon dioxide (C0 2 ), nitric oxide (lTO), nitrogen dioxide (no 2 ), sulfur dioxide (S0 2 ), formaldehyde (IlCIIO), and respirable particula_tes; sidestream tobacco smoke contains CO, co 2 , no, no 2, respirable particulates and a wide range of organic compounds. The degree of indoor air pollution and, therefore, the degree of health risk to occupants from these sources depends on the type and amount of pollutants entering the occupied space, and the rate of removal by processes such as infiltration, mechanical ventilation, and chemical reactions.Calculating emission rates of these combustion-generated pollutants is an essential step in assessing the degree to which these pollutant sources affect indoor air quality. In this paper, we report the pollutant emission rates derived from our studies of a gas-fired stove, gasfired unvented space heater, kerosene-fired unvented space heater, and sidestream cigarette smoke. EXPERIUEUTALExperiments were carried out in an environmental chamber under controlled ventilation conditions; our Hobile Atmospheric Research Laboratory (ltARL) was used to measure gas-phase pollutant concentrations.-1-Both the 27-m 3 environmental chamber and the l~ are depicted schematically in Fig. 1. The chamber can be operated under conditions of natural infiltration, typically providing· less than half an air change per hour (ach), or under mechanical ventilation, providing higher air exchange rates. Small, variable-speed fans centered on each chamber wall provide mixing of the air to insure unifo...