Showing 401 results for Ag
M. Mahlooji, S.f. Mousavi, M. Karimi,
Volume 4, Issue 1 (4-2000)
Abstract
A study was conducted to determine irrigation scheduling of pinto bean and to evaluate the effect of its planting date. A split-plot with complete randomized block design with four replications was used at Isfahan University of Technology Research Station in Shervedan-Falavarjan, The main plots were three irrigation regimes of T1 to T3 (irrigation after 50±3, 70±3 and 90±3 mm evaporation from class A pan, respectively) and the sub-plots were two planting dates of May 28 and June 28.
The results showed that delayed planting from May to June caused earlier flowering, physiological maturity and reduction of 29.6% in grain yield. Grain yield in T1 to T3 treatments were 3585.1, 3510.5 and 1925.8 kg/ha, respectively. The difference between grain yields of T1 and T2 with T3 treatments were significant at 1% probability level. Biological yields at May 28 and June 28 planting dates were 8257.1 and 5535 kg/ha, respectively, which were significantly different. There was no significant difference between biological yields of T1 and T2 treatments. Number of pods per square meter was the most important component of grain yield and 85% of grain yield difference was due to this part. Harvest index was affected by irrigation treatment and planting date. Mean harvest indices for T1 to T3 treatments were 45.5, 46.1 and 37%, respectively, and 42.8% and 44.9% for the two planting dates. Water use efficiencies for grain yield in T1 to T3 treatments were 0.557, 0.556 and 0.329 kg/m3, respectively. Generally, treatment T2 was shown to be the best irrigation regime.
A. Hassanli, A. Sepaskhah,
Volume 4, Issue 2 (7-2000)
Abstract
In this study, seven citrus gardens in different parts of Darab were chosen to evaluate the drip irrigation systems. The evaluation process was based on the Merriam and Keller’s model (1978). Besides the evaluation of drip irrigation systems, the water requirement of citrus was estimated using four models including Blany-Criddle modified by FAO, Hargrive-Samani, Pan Evaporation and Solomon-Kodama model. On the basis of the results obtained by Hargrive-Samani with 1296 mm annual water requirements, a comparison was made between irrigation with existing systems and irrigation under favorable and desired conditions.
The results from field measurements indicate a considerable reduction in the emitter discharges. The low pressure and emitter clogging could be two major reasons for the problem. Low pressure at head control, topography, head losses and also using no filter(s) or unefficient filters are the main reasons for the reduction. In some gardens, overirrigation even up to 2.5 times of water requirement was practiced by using extra emitters and increased irrigation times. Overirrigation causes considerable water losses through deep percolation and in reased overwetting area.
Field measurements indicated a good emission uniformity (EU) for the fields with overirrigation. EU in chosen fields varied from 40 to 91%, AELQ varied from 31 to 82% (poor to good) and PELQ varied from 36 to 82%. This study showed that most farmers are not familiar with plant water requirements. The fields with efficient filtration due to using extra emitters per plant are mainly overirrigated. But fields without any filter of unefficient filters are not irrigated sufficiently. The very high manufacturing variation coefficient of IEM emitters (Cv=0.22), which are widely used in Darab, causes a design emission uniformity of 55%.
I. Malek Mohammadi, A. Shafii Alavijeh,
Volume 4, Issue 2 (7-2000)
Abstract
Mutual understanding among officials and followers has been a point of concern in behavioral management. Natural resources extension which, from the very first step, is concerned with the exploration of practical problems is in serious need of an atmosphere of mutual understanding between agents and clientele. In this research, attention was drawn toward the measurement of mutual understanding between executives and nomads regarding nomads’ problems in utilizing natural resources and breeding cattle in Isfahan Province. For this purpose, initially, understanding between nomads and natural resources administrators (extension agents and specialists) regarding their respective problems were measured and compared. The research population of the study consisted of two groups. The first, involved 32 administrators, extension agents and specialists, and the second, 75 nomad families. Two different questionnaires were developed for the study as research instruments in which 52 items regarding nomad problems were included. Each part of the population was asked to rank the items accordingly. Then, some nonparametric tests such as Kruscall Wallis and Mann Whitny U tests were applied to compare the mean rank for each item within and between the two groups.
Results showed that the administrators and nomads had different attitudes in only two of the 52 items. Administrators had no statistically significant different attitude in 52 problems. Eliminating the discriminating items, the attitudes in only two groups were compared and results showed that they had no significant difference in the remaining 48 items. Therefore, extension agents can follow these problems based on their mean rank priority in their developmental projects. This method of data reduction and understanding field constraints can be applied to the studies dealing with planning agricultural and/or natural resources development projects through extension education.
A. Eghtedary Naeeny, H. Ghadiri,
Volume 4, Issue 2 (7-2000)
Abstract
In order to find the critical period of weed control, the best time of weed control beginning (i.e. herbicide application time), and the length of weed control period (i.e. herbicide persistency) in corn, field experiments were conducted in Bajgah and Kooshkak in Fars Province in 1995 using a randomized complete block design with 14 treatments and four replications. Treatments consisted of different times of weed control beginnings (20, 30, 40, and 50 days after corn emergence), different duration of weed control periods (10, 20, and 30 days), a weedy check, and a weed-free check during the period of corn growth.
In Kooshkak, a 10-day duration of weed control period had significantly lower corn yields than 20 and 30-day periods. In Bajgah, a 10-day weed control period had significantly lower corn yields than a 30-day period. Time of weed control beginning was not significant at both locations however, the interaction between beginning time and the duration period of weed control was significant. It appears in both locations that a minimum 20-day control period at the initial stages of corn and weed growth, and a minimum 30-day control period before corn pollination are necessary to prevent corn yield losses. In order to prevent corn leaf area decline at both locations, a 20-day weed control period until 40 days after crop emergence is necessary.
A. Mirlohi, N. Bozorgvar, M. Bassiri,
Volume 4, Issue 2 (7-2000)
Abstract
In order to determine the most suitable cultivar and N level based on yield and silage value of forage sorghum, an experiment was conducted in summer 1995. The experiment was arranged in a split-plot design with four replications. Two levels of N (300, 500 Kg/ha urea) were the main plots and the subplots were three sorghum hybrids (Sugar graze, Super dan and Speed feed). Seeds were hand sown on June 29 with an inter row space of 50 cm and a final density of 20 plant/m2.
The results showed that when the N rate increased, forage yields and percent of protein in forage and silage increased. Also panicle dry weight increased at anthesis. The N rate had no significant effect on other traits. A significant difference was observed among hybrids for all characteristics measured. Sugar graze with a bigger stem diameter was taller and produced higher number of leaves. At anthesis, plant leaf and stem dry weight was also highest for Sugar graze however, the highest panicle dry weight belonged to Speed feed. There was a significant interaction between hybrids and N levels for dry matter production. The percent of leaf, stem and panicle dry matter was highest in sugar graze, Super dan and Speed feed, respectively. The Sugar graze produced the highest forage and dry matter yield. This hybrid produced 30 ton/ha of dry matter and 97 ton/ha of forage, respectively.
Furthermore, this cultivar had the highest percent of forage crude protein (7.45%) and the least percent of forage crude fiber (25.12%). Ensiling caused a decrease in percentage of crude protein and an increase in crude fiber. The Sugar graze and Speed feed had the highest and lowest dry matter digestibility, respectively. Based on the results obtained from this study, Sugar graze was found to be the most suitable hybrid due to its highest forage and dry matter yield and better silage quality. Higher N rate (500 kg/ha) is also recommended for higher forage yield and higher percentage of protein.
K. Zibai, B. Hatami,
Volume 4, Issue 4 (1-2001)
Abstract
The efficiency of singular and joint usage of third larval instars of ladybeetle, Hippodamia variegata (Goeze) and green lacewing, Chrysoperla carnea (Steph.) was studied against cotton aphid, Aphis gossypii Glover on cucumber plants in greenhouse.
The predator-prey ratio of 1:30 reduced the population of pest significantly. Singular and joint usage of predators, however, was not significantly different. The predator-prey ratio of 1:90 reduced the population of host significantly but the treatment with larvae of both predators and the treatment with only ladybeetle larvae were not significantly different. However, only the treatment with lacewing larvae was significantly different from the two above-mentioned treatments.
Y. Rezaenejad, M. Afyuni,
Volume 4, Issue 4 (1-2001)
Abstract
Due to high production of organic residues such as sewage sludge and compost, land application is probably the best way to prevent accumulated residues in the environment. However, the risk involved in the land application of organic residues should be evaluated prior to the assessment of their economic and fertilizer values. The objective of this study was to evaluate the effect of organic residues on soil chemical properties, yield and uptake of heavy metals and nutrients by corn (Zea mays L.). The study was a randomized complete block design with three replications with four treatments including cow manure, sewage sludge, municipal compost and inorganic fertilizer.
The organic amendments were applied to the plots at a rate of 50 t ha-1 and inorganic fertilizer treatment consisted of 250 kg ha-1 ammonium phosphate and 250 kg ha-1 urea.
Organic amendments significantly increased soil organic matter content, EDTA-extractable Fe, Zn, Cu and Pb and plant available P, K, and N. Uptake and concentration of nutrient in corn grain and shoots were significantly affected by treatments, whereas Cd and Pb concentrations were the same among the treatments. Cow manure and sewage sludge treatments had the highest and compost had the lowest corn silage and grain yields. Overall, the results indicated that cow manure and sewage sludge had a high fertilizer value and led to heavy metal concentrations in soil as well as corn tissues which were much lower than the reported standards.
S.h. Dokhani, L. Rabiei Motmaen,
Volume 5, Issue 1 (4-2001)
Abstract
Physicochemical characteristics of potato (Solanum tuberosum L.) are very important for storage and processing qualities. The amount of reducing sugars (glucose and fructose) and organic acids at harvest, during and after storage is the most important factor. In this study, three potato cultivars (Moran, Marfona and Agria) were collected, dry cleaned and graded into three sizes. They were analyzed for specific gravity and dry matter content. Potato tubers were stored at 4°C and about 85% R. H. for 15 weeks and then reconditioned at room temperature (25±l)°C for 4 weeks. During the storage period of tubers, sugars (sucrose, glucose and fructose) were analyzed on a weekly basis, but citric, D-malic and D-pyroglutamic were analyzed on a monthly basis by high performance liquid chromatography (HPLC). Data were analyzed statistically in a completely randomized design with sampling and Duncans multiple range test.
The total sugar and organic acid contents of tubers significantly increased during the 15 weeks of storage at 4°C and decreased after reconditioning at room temperature. The size of tubers did not affect the accumulation of total sugars. Dry matter content and specific gravity of Agria tubers were higher than those of both Moran and Marfona. Also accumulation of reducing sugars was lower in Agria than in Moran and Morfona initially and after the storage and reconditioning periods. Therefore, Agria must be suitable for processing into chips or dry powder.
A. Mirlohi, M.a. Hajabassi, S.j. Razavi, E. Ghanaati,
Volume 5, Issue 1 (4-2001)
Abstract
Soil loss due to erosion is a common problem in most parts of Iran. Reduced soil organic matter and lack of proper agricultural management have intensified the problem in recent years. Conservation tillage systems are becoming more widely used in corn production in other parts of the world because of soil losses due to wind and water erosion and energy inputs. Changes in tillage methods, however, create different environments for the germination, development and maturation of corn plants. Most corn hybrids have been selected and developed under conventional tillage systems but these hybrids mayor may not be well adapted to both systems. This study aims to evaluate the performance of five locally grown corn hybrids under zero and conventional tillage methods. The experiment was conducted for 2 years on a plot of land specified for this study. Experimental design was a split plot with randomized complete block arrangement and four replications.
Seedling and juvenile plant growth were not affected by tillage method and were similar for all hybrids. Plant dry matter was affected significantly by the cropping system and was lower in no-till method. Plant leaf area index and stem diameter reduced significantly in the no-till system. Reduction was greater in the second year of the experiment. Also grain yields were significantly different among years, tillage method and plant genotypes. Yield reduction was highest in the second year of the experiment under no-till cropping system. There was no interaction between tillage method and corn genotypes, indicating that, usually genotypes perform similarly with regard to grain yield under both tillage methods. The results suggest that corn production under no-till system in Isfahan is probably associated with yield reduction.
A.r. Sadeghi Mahounack, F. Shahidi,
Volume 5, Issue 1 (4-2001)
Abstract
The antifungal effect of sodium diacetate on inhibiting the growth of some bread spoiling molds was examined both in culture media and in flat bread “In situ”. In the first step, the antifungal effect of different concentrations of sodium diacetate: 0, 1000, 2000, 3000, 4000, and 5000 ppm were examined against Aspergillus sp., Aspergillus niger, Rhizopus sp., and Penicillium sp.
The results indicated that as the concentration of sodium diacetate increased, the mold growth decreased. At 5000 ppm the mold growth was inhibited up to fifth day (the last day of experiment). Based on these results, the antifungal effect of different concentrations of sodium diacetate was evaluated in bread “In situ”. In this stage Aspergillus sp. was selected as the indicator mold. The results indicated that if 3000 ppm of sodium diacetate is used, not only mold growth is inhibited but bread staling can also be prevented. This concentration of sodium diacetate does not have any harmful effect on texture and flavour, and can increase bread shelf life up to four days. Higher concentrations of sodium diacetate can inhibit mold growth completely, but have negative effects on texture and flavour. Therefore, 3000 ppm of sodium diacetate is recommended for increasing bread shelf life.
J. Torkamani,
Volume 5, Issue 2 (7-2001)
Abstract
The main objective of the present study is to analyze the effects of agricultural crop insurance on farmers’ technical efficiency and risk attitude. Required data came from questionnaires that were completed by the Institute for Planning and Agricultural Economics of the Ministry of Agriculture. Farmers’ technical efficiency and attitude toward risk were estimated using stochastic frontier production function and equally likely certainty equivalent method for both insured and non-insured groups. Results revealed that effects of agricultural insurance on farmers’ technical efficiency were significantly positive in the three study regions.
Results of estimating risk aversion coefficients of study farmers showed a positive effect of insurance on risk aversion coefficients. However, this effect was significant only in two of the climatic regions under study.
M. Afyuni, M.r. Mosaddeghi,
Volume 5, Issue 2 (7-2001)
Abstract
Tillage system effect, Conventional (CT) vs. No-Till (NT), on soil physical properties and Br transport was studied at two locations in North Carolina. The soil types were a Typic Paleudults at Coastal Plain (site 1) and a Typic Kanhapludults at Piedmont (site 2). Bulk density (BD), total porosity (TP), macroporosity (MP), and saturated hydraulic conductivity (Ks) .were measured in plant row (R), and trafficked (T) and untrafficked (N) interrows. A rainfall simulator was used to apply two early season rainfalls to 1 m2 plots where KBr suspension was surface applied for Br leaching study. The first simulated rainfall event (30 min) consisted of a low (1.27 cm h-1) or a high (5.08 cm h-1) rate applied, 24 h after Br application. One week later, the high rainfall rate was repeated on all plots.
Soil samples were taken two days after applying first and second simulated rainfall (a week between them) and the end of season from different depths for measuring Br concentrations. Soil physical properties were affected by both tillage system and position.
Bulk density was higher in NT versus CT and in T position versus Rand N positions. Total porosity was lower in NT versus CT but MP was significantly higher in NT. Saturated hydraulic conductivity was about 90% lower at T position versus N and R positions. Coefficient of variation was quite large, making it difficult to obtain statistical differences between tillage systems. The surface l0-cm of soil contained the highest Br concentration for depth treatments with treatment differences occurring primarily in 0 to 25 cm depth. In first and second sampling dates, more Br leached under NT versus CT system. However, there was no significant difference between the two tillage systems in Br leaching at the end of the growing Season. In site 1, Br leached more due to the coarse texture and high Ks of the soil.
M.r. Khajehpour, F. Seyedi,
Volume 5, Issue 2 (7-2001)
Abstract
Sensitivity of developmental stages of three sunflower cultivars to day length and temperature changes under field conditions were evaluated, and their development rates during various growth stages were modeled in a field experiment conducted in 1996 at the Agricultural Research Station, Isfahan University of Technology. Five dates of planting (April 27, May 12 and 27, and June 12 and 29) and three open pollinated sunflower cultivars (Record, Vnimik 8931 and Armavirec) were evaluated using a randomized complete block design with split-plot layout in three replications. Date of planting was considered to be the main plot and cultivars were randomized in sub-plots.
Number of days from planting (P) to head visible (HV) and P to first anther (FA) were significantly reduced with delay in planting as the result of increase in temperature during these periods. Number of days from P to physiological maturity (PM) was also significantly reduced with delay in P. This response, however, could not be explained by changes in temperature variables or day length. Number of days from HV to FA, in harmony with the partial stability of maximum and minimum temperatures during this period, was not affected by date of planting. Duration from FA to PM of the last planting date was significantly shorter than the other planting dates. This response was related to the persistence of the effect of high and stable maximum temperatures prevailing during HV to FA period of the last planting date. Armavirec was significantly earlier than Record and Vnimic 8931 for number of days from P to HV and from P to FA Cultivars showed significantly large differences for the FA to PM and P to PM durations. Armavirec was the earliest and Record was the latest cultivar. Based on the results obtained, it may be concluded that the cultivars under study were non-sensitive to photoperiod. Development rate (DR) of Armavirec responded linearly and DR of Record and Vnimic 8931 responded non-linearly to increases in temperature variables during P to HV and P to FA Development of Vnimic 8931 was faster than Record at high temperatures. DR of the cultivars decreased linearly during P to PM as day length increased. The relationship between DR and photoperiod could be used as a practical model for estimating P to PM duration of these sunflower cultivars.
A. Hemmant, O. Taki,
Volume 5, Issue 2 (7-2001)
Abstract
Any mechanical force exerted on a potato tuber during the harvesting may result in mechanical damage. A few weeks prior to harvesting, haulm destruction could improve the rheological properties of the tuber and reduce its susceptibility to mechanical damage. The effects of elevator and oscillatory sieve diggers and haulm destruction on potato loss and mechanical damage were studied on a farmer field in Fereidan region of Isfahan. Two haulm management treatments (destruction and non-destruction) along with five potato diggers (elevator digger with a long main web and with agitator, elevator digger with primary and secondary webs and with agitator, elevator digger with a main web and with/without agitator, and reciprocating riddle digger) were laid out in a strip block design within a randomized complete block design with four replications. The main crop variety, namely Marfona, was planted in the field.
The results showed that the percentages of undigged and soil-covered tubers were significantly different among the potato diggers tested. These losses were due to the dices located to the sides of shares or gage wheels and wrong adjustments on the diggers. Comparing the performance of reciprocating riddle with elevator diggers, its sieving capacity was low and the severity of the mechanical damage and the numbers of tubers covered with soil were high. Haulm destruction was effective in reducing the peeler type damage (the less than 3 mm deep damage to flesh). Although the elevator digger with a main web (elevator chain) and without agitator had the least mechanical damage index, the differences among the elevator diggers tested were not significant (5%).
N. Sakenian Dehkordi, B. Ghobadian, S. Minaei,
Volume 5, Issue 2 (7-2001)
Abstract
A suitable instrument capable of inserting mulch into soil is needed to improve soil water holding capacity. The goal of this research is to design and manufacture an instrument with a blade and mechanism that can insert rice mulch into the soil. All the parameters in sub-soiling operation were taken into account, and the technique presented can be recommended as a special method of injecting rice husk. The instrument designed was easy to use on a tractor. Sub-soiling operation and husk injection were carried out satisfactorily using various amounts of husk and at different soil depths. This method was added to the conservation chart presented by Morgan as an integrated technique.
E. Rowghani Haghighi Fard, M.j. Zamiri,
Volume 5, Issue 3 (10-2001)
Abstract
Three levels of urea (0, 0.5 and 0.75% on fresh weight basis) were added to whole corn plants to investigate their effects on the chemical composition, and digestibility in 16 Ghezel male lambs using a completely randomized design. Rumen degradability and nutritive values were also evaluated.
pH, total nitrogen and ammonia-N concentration of silages increased (P<0.05) with the addition of urea. Total nitrogen apparent digestibility was higher (P<0.05) with the urea addition. Nitrogen balance in ruminal fluid increased (P<0.05) with the addition of 0.5% urea. pH and ammonia-N concentration increased (P<0.05) with the addition of urea until 1.5 hr post feeding. Blood serum urea nitrogen concentration was higher (P<0.05) with the addition of urea until 6 hr post feeding. Potential degradability of dry matter and organic matter was higher at 0.5% urea level. Average daily gain increased with the urea addition and was highest (212.88 gr) at 0.75% urea. Subcutaneous fat depth was significantly (P<0.0l) lower for the sheep fed with 0.5% urea-treated silage as compared to other treatments. The results indicated that feed efficiency may be improved by urea addition and that the addition of urea (0.5% on fresh weight basis) may be recommended in order to increase the feeding value of whole corn plants.
R. Ebadi, R. Jafari, F. Majd, G.h. Tahmasbi, H. Zolphagharieh,
Volume 5, Issue 3 (10-2001)
Abstract
In this study, the control method of greater wax moth using male sterilization technique with gamma ray and chemical control methods were examined and compared. In order to determine the safe and effective dosage of gamma-ray to sterilize male pupae of the greater wax moth, an experiment was conducted in a complete randomized design with 5 treatments and 3 replicates with 50 male pupae in each replicate. Treatments included different levels of gamma-ray dosages with zero, 250, 300, 350 and 400 gray.
Release ratio of sterile to normal males was also studied in a similar experiment. Treatments included sterile-males, normal males and virgin females with the ratios of 1:1:1, 2:1:1, 3:1:1, 4:1:1 and 5:1:1. In this study, male pupae were irradiated with 350 grays of gamma-ray. The possible parthenogenetic reproduction of this pest was also studied. In order to compare the results from the male-sterile technique and the chemical control of this pest, another experiment was conducted in wax stores using 3 treatments with 3 replicates. Phostoxin was used as the most common chemical pesticide with a dosage of 1 tablet of 3 grams of 56% per 1 m3 space for the control of this pest.
The results showed that the best dosage to sterilize male pupae of the greater wax moth was 350 grays of gamma-ray. Also the best release ratio was four sterile male, one normal male for each normal female (4:1:1). Our results indicated that the females of the greater wax moth were not able to reproduce through parthenogenesis. There was no significant difference between the chemical and male-sterile methods for the control of this pest.
B. Hatami, H. Ghahari,
Volume 5, Issue 3 (10-2001)
Abstract
Regarding the importance and high potential of
Encarsia formosa Gahan (Hymenoptera: Aphelinidae) for control of the greenhouse whitefly,
Trialeurodes vaporariorum Westwood (Homoptera: Aleyrodidae), the effect of different diets and storage of the parasitoid at low temperatures on its longevity and efficiency was studied. The average longevity of the parasitoid on different diets including honey-syrup 15%, honey-syrup 10%, sucrose syrup 15%, honeydew of whitefly were significantly different at 1% from distilled water and control (without water and food) treatments.
Change in honey-syrup concentration at a range of 5% did not affect the longevity of the parasitoid. The honeydew and sucrose-syrup treatments were not significantly different. This was probably due to the relative similarity of food quality of these two diets. Storage of host parasitized nymphs containing pupae of 1-2 days-old of E. formosa at 8±1°C affected the emergence rate and efficiency of adult parasitoids.
Four treatments including the pupae of parasitoids in 4th nymphal instars of the greenhouse whitefly were stored at 8±1°C for 5, 15, 25 and 35 days. Control treatment included pupae of parasitoid that were held at room temperature, 24±4°C. Host nymphs were parasitized by the parasitoids emerging from all treatments. The average parasitized nymphs by parasitoids emerging from 5, 15 days and control treatments were not significantly different at 1 %.
M. Abdollahi Ezzatabadi, G.r. Soltani, A. Nejati,
Volume 5, Issue 4 (1-2002)
Abstract
In this paper, a simple farm management information system is introduced. This system was administered through cooperation between farmers and an information agency. The results showed that the farmers were willing enough to accept the system. Nevertheless, having an accounting system is the first step toward the establishment of an information system, which is used by only %42 of the sampled farmers. The main reason for this is the lack of knowledge about the benefits of such systems. In other words, if farmers were aware of the benefits of accounting systems, they would accept them easily. The results also showed that the farmers who use accounting systems are more successful in their production activities.
H. Salami, A. Kiani Rad,
Volume 5, Issue 4 (1-2002)
Abstract
This study uses the Generalized Composite Commodity Theorem (GCCT) to investigate the consistency of aggregating major crop products in studying producer’s behaviour in Iran. The results show that all crop products, except corn, soybean, and melon can consistently be grouped into cereals, oil seeds, pulses, and vegetable composite commodities. In addition, the results testing the hypothesis of the possibility of aggregating all crop products in a single group was positive when we excluded sesame, cotton, and water melon from the list. Accordingly, modeling and estimating an aggregate production or cost function for Iranian crop sector will not cause consistent biases. Additionally, one can estimate a separate or cost function for each of the above sub-sectors without causing aggregation biases in grouping the commodities.
