PH—Postharvest Technology: Dielectric Properties of Common Bean

This paper discusses the variation of relative permittivity, dielectric loss factor, loss tangent, and a.c. conductivity of common bean, Phaseolus vulgaris L., variety Campeão-3 from 75 kHz to 5 MHz. Included are curves showing the variation of these dielectric properties on moisture and bulk density. The variation of relative permittivity on frequency, moisture content, and density was more regular compared to the behaviour of the other dielectric properties in that it continuously increases with moisture and bulk density and decreases with frequency. The conclusion is that of all dielectric properties the relative permittivity should provide less error in common bean moisture content determination.     

PH—Postharvest Technology: Thermodynamics of Moisture Sorption in Sesame Seed

Experimental data on the sorption isotherms of sesame seed were used to determine the thermodynamic functions (heat of vaporisation, spreading pressure, net integral enthalpy and entropy). The heat of vaporisation decreased with increase in moisture content and approached the latent heat of pure water at moisture content between 18 and 21% dry basis. The spreading pressure increased with increase in water activity and was not significantly affected by temperature. Net integral enthalpy decreased with increase in moisture content, and became asymptotic as the moisture content of 12% was approached. Net integral entropy decreased with increase in moisture content to a minimum value of 0·138 J kg⁻¹K⁻¹ at moisture content of about 3·7%. It then increased with moisture content to a maximum of about 0·63 J kg⁻¹K⁻¹ at about 12% moisture content and thereafter, remained nearly constant.     

PH—Postharvest Technology: Surface Gloss and Weight of Eggplant during Storage

Surface gloss and weight loss are two important parameters to judge the freshness of eggplant. Data were collected in order to develop some quick and reliable instrumental methods to determine these. Surface gloss and weight loss of eggplant stored for 0–96 h at 80–84% relative humidity and 20°C temperature were determined using a computerized spectral radiometer and a precision electronic balance, respectively. The surface gloss was quantified in terms of gloss index, and a relationship between weight and gloss index during storage of eggplant was established. Gloss index and weight both decreased quadratically with storage period. Major changes were observed in the first 48 h of storage. Weight and gloss index of eggplant during storage were found to be correlated linearly.     

PH—Postharvest Technology: Automatic Jalapeño Chilli Grading by Width

Jalapeño chilli is a variety grown extensively in Mexico consumed by almost all the population. It has a high processing demand and proper sorting is required before filling or canning. A sorter that classifies chilli by three different width sizes was built. The conveyor used baby suckers to align each chilli during sensing. Chilli width was determined by means of a photodiode scanner, which detected the incoming radiation sent by a laser line generator. Chillies presenting necrosis were detected with a radiometer and removed to increase product quality. The accuracy on the necrosis detection and width classification was of 96·3 and 87%, respectively.     

PH—Postharvest Technology: Some Aspects of the Mechanical Properties of Shea Nut

Compression tests were carried out on pre-treated shea nuts to study the effects of moisture content, temperature and loading position on rupture force, deformation, toughness and firmness at the point of failure. All factors were examined and most of their interactions had significant effects on the measured para-meters at 0·05 level of significance. Rupture force and firmness decreased while deformation and toughness increased with increases in moisture content in both horizontal and vertical loading positions. The results provide useful data to be used by engineers in the design of suitable shea nut cracker.     

PH—Postharvest Technology: The Effects of Grain Temperature on Breakage Susceptibility in Maize

To understand the viscoelastic characteristics (i.e. hardness) of the maize (Zea Mays L.) grain in relation to high-temperature drying, a breakage tester (HT-I drop tester) was developed and single-grain breakage at various grain temperatures and times after drying was determined. Both hard and soft maize hybrid varieties had minimal breakage at high grain temperatures (78–110°C), while decreasing grain temperature increased breakage exponentially. After drying at both 60 and 120°C, the percentage breakage measured at ambient temperature increased rapidly during cooling in air at an ambient temperature of 20°C and a relative humidity in the range 65–70%. Breakage reached a maximum after about 10 min from the start of cooling. A Mitscherlich function described the chronological development of percent grain breakage. Analysis of the function parameters for the extent (maximum) and rate of breakage indicated that there was a significant interaction between variety and drying temperature for the development of grain breakage after drying. These results indicated that grain temperature should be considered as a co-factor when assessing grain breakage susceptibility.     

SE—Structures and Environment: Compost Airflow Resistance

Four bulking agents, pine shavings, mixed (long and chopped) grass hay, chopped grass hay and long (whole) wheat straw, were each mixed with pig slurry and tap water to obtain three moisture contents (MC) of 60, 65 and 70%. Quadruplets of each treatment were placed in laboratory composting vessels with a capacity of 105 l and a composting depth of 0·95 m. Using the air plenum at the bottom of each vessel, air was forced at apparent velocities of 0–0·002 m s⁻¹ through each compost mass to measure the air static pressure drop across the compost mass as a function of apparent air velocity. Airflow resistance values were measured for compost depths ranging from 0·55 to 0·85 m. Following this test, all mixtures were aerated for 21 days of composting without overturning. The static pressure measurement procedure was then repeated on all quadruplet mixtures.The air static pressure drop was found with respect to a packed bed under laminar flow, defined using the particle size distribution, porosity, depth and airflow channel characteristics of the compost material. Although MC affected the value of the airflow channel characteristics of the compost material, both the hay and straw demonstrated similar values, while shavings demonstrated values more variable and wider values for MC between 60 and 70%.There was a significant increase in airflow resistance after 21 days of composting, which supports the need for compost overturning to reestablish the material's structure and to restore the airflow channels or pores.     

Soil Boron Fractions and Response of Green Gram in Calcareous Soils

A greenhouse experiment with green gram on boron (B) deficient calcareous soils was conducted for two years at Ludhiana (Punjab), India to study soil B fractions and response of green gram to B application. Three soils with calcium carbonate (CaCO₃) content 0.8 (Soil I), 2.1 (Soil II) and 4.6 (Soil III) percent were collected from different sites of Ludhiana and Bhatinda districts, Punjab, India. The treatments comprised of five levels of soil applied B (0, 0.5, 0.75, 1.0, and 1.5 mg B kg^?1). The experiment was laid out in completely randomized design (CRD) factorial design with three replications. Readily soluble B comprised 0.39 to 0.76 percent in Soil I, 0.32 to 0.54 percent in Soil II, and 0.21 to 0.34 percent in Soil III of the total B, taking into account of all the levels of B applied at both stages of crop growth. Readily soluble B increased with increasing application rates of B and decreased from grand growth stage (40 days after sowing) to maturity of the crop. Specifically adsorbed, oxide bound, residual, and total B was higher in Soil III as compared to Soil II or Soil I. At maturity, specifically adsorbed B converted into other fractions to maintain equilibrium in soil solution. Organically bound B was greater than oxide bound B. Among all fractions, the residual fraction accounted for the major fraction of the total B. Soil application of lowest level of B was adequate to cause significant increase in dry matter yield and seed yield of green gram regardless of type of soil.     

AP—Animal Production Technology: Predicting Sensor Placement Targets on Pigs using Image Analysis

This work forms part of a longer-term project aimed at developing a robot to bring a sensor into contact with an animal. The example application is to place an ultrasonic sensor onto the back of a pig as it uses a feeding stall. This paper presents the accuracy required in placing the sensor, and the accuracy of target location achieved using a linear function of landmark points on the pig outline, located by image analysis.The P2 standard position is close to a local minimum in fat thickness. When the target is chosen to be 25 mm ahead of the last rib and 50 mm from the mid-line of the pig, then a positional error of ±10 mm laterally and ±25 mm longitudinally will give a backfat measurement within 5% of the minimum.A linear model predicting the target position from six points on the outline was trained on 7549 images and tested on 2978 images. On the test data the root means square (r.m.s.) errors in the X and Y directions were 16 and 38 mm, respectively. A linear model with separate offset terms in X and Y coordinates for each sequence gave r.m.s. errors of 6 and 8 mm. However, this requires the offset value to be calculated for each sequence. An active system is proposed where multiple measurements from each pig will be used to improve the backfat estimate to within 5% of the minimum value.     

模拟酸雨对水稻、玉米和绿豆萌发及生长影响

通过模拟试验研究酸雨对水稻,玉米和绿豆的萌发及生长的影响,结果表明,ｐＨ２．０的模拟本雨明显降低作物的发芽率,伤害植物叶片,造成叶片细胞膜透性增加,使叶绿素含量,通过氧化氢酶和脱氢酶活性降低,ｐＨ３．０以上模拟酸雨短期内对作物无明显影响。     

IT—Information Technology and the Human Interface: Reliability of Cotton Pickers and its Effect on Harvesting Cost

In this study, the reliability of cotton pickers is analysed and its importance in studying the performance of harvesting systems is examined. A theoretical development of farm machinery and specifically of cotton-picker reliability is presented and an algorithm based on the exponential distribution is developed. This algorithm is then applied to predict picker reliability, delays caused by machine breakdowns and their implications upon the cotton area harvested as well as the associated harvesting cost for a cotton producers group in Greece. The results obtained have shown a machine breakdown every 23·7 h with an average repair time of 2·86 h. Within a harvesting season, a cotton picker undergoes on average 12·75 breakdowns and 4 days out of work. This means a reduction in the least cost area harvested of 20% and an increase in the harvesting cost of 6·5%.     

Suitability of Lime,Green Leaf,and Farm Yard Manure and Inorganic Fertilizers for Sustaining Green Gram Yield and Rainwater Use Efficiency Under Moist Sub-Humid Alfisols in India

Field experiments were conducted to assess the effect of nutrients management practices on yield and rainwater use efficiency of green gram (Vigna radiata), and soil fertility under moist sub-humid Alfisols at Phulbani, India, during 2005–2008. Ten treatment combinations of lime @ 10% and 20% of lime requirement (LR) @ 8.3 t ha^?1, farmyard manure (FYM) @ 5 t ha^?1, green leaf manure @ 5 t ha^?1, and nitrogen, phosphorus, and potassium (N–P–K) (20–40–20 kg ha^?1) were tested. The analysis of variance indicated that treatments differed significantly from each other in influencing yield and rainwater use efficiency. Application of lime @ 20% LR + FYM @ 5 t/ha + 40 kg P + 20 kg K ha^?1 was superior with maximum mean yield of 531 kg ha^?1, while lime @ 10% LR + FYM @ 5 t ha^?1 + 40 kg P + 20 kg K ha^?1 was the second best with 405 kg ha^?1 and maintained maximum soil fertility of nutrients. The superior treatment gave maximum sustainability yield index of 67.5%, rainwater use efficiency of 0.49 kg ha^?1 mm^?1, improved soil pH, electrical conductivity, and soil nutrients over years.     

SE—Structures and Environment: Ammonia Emissions from Broiler Manure — Influence of Storage and Spreading Method

Knowledge is poor concerning losses of ammonia from broiler manure during storage and after spreading. Broiler manure was stored from October to May in two separate heaps, one uncovered and one covered with a 30 cm layer of straw. Ammonia emissions were measured with a micrometeorological mass balance method in five separate periods during storage. Ambient air temperature and temperatures in the heaps were recorded continuously. After storage, broiler manure from the uncovered heap and commercial fertilizer pellets including broiler manure were spread to arable land at a rate of 110 kg [total-N] ha⁻¹. Ammonia emissions were measured with an equilibrium concentration method from plots fertilized with broiler manure and pellets, respectively, with and without harrowing 4 h after spreading. Temperature measurements taken in the heaps during storage indicated high biological activity. The highest temperatures were recorded in the straw-covered heap. Cumulative ammonia losses were 7% of total nitrogen from the uncovered heap and 10% from the heap with cover. Totally, 13·5% of the nitrogen in the broiler manure was lost as ammonia after spreading without incorporation of the manure and 7·5% from plots with incorporation. After incorporation no ammonia emission occurred. No emissions occurred from plots fertilized with pellets.     

SE—Structures and Environment: Biofiltration of Odour and Ammonia from a Pig Unit—Biofiltration of Odour and Ammonia from a Pig Unit—a pilot-scale Study

A pilot-scale biofiltration unit was constructed at a pig finishing building on the University College Dublin research farm. The biofiltration system was investigated over three trial periods. Exhaust air from a single pen was extracted by a variable speed centrifugal fan and passed through a humidifier and biofilter. A 0·5 m depth of woodchips of over 20 mm screen size was used as the biofilter medium. The moisture content of the medium was maintained at 64±4% (wet weight basis) for trial one and 69±4% (wet weight basis) for trials two and three using a load cell method. The volumetric loading rate varied from 769 to 1898 m³ [air] m⁻³ [medium] h⁻¹ during the three trial periods. Odour and ammonia removal efficiencies ranged from 77 to 95% and 54 to 93%, respectively. The pH of the biofilter leachate remained between 6 and 8 throughout the experimental periods. The pressure drop across the biofilter ranged from 14 to 64 Pa. It is concluded that a wood chip media particle size >20 mm is suitable for use in biofiltration systems on intensive pig production facilities. This will minimize the pressure drop on the system fans to reduce overall operation costs. It is recommended that a filter bed moisture content (wet weight basis) of greater than 63% be used to maintain overall efficiency. An efficient air moisturizing system (humidification and bed sprinkling) along with a properly designed air distribution system must be incorporated in the overall design when operating at such high volumetric loading rates.     

Estimation of density—Moisture—Stress functions from uniaxial compression of unsaturated, structured soils

A quasi-theoretical soil compaction model is presented which gives good estimates (r²=0.980−0.995, P<0.001) of the complete density-stress compression line for soils of variable initial moisture content under static loads from 0 to 1.0 MPa. The 3 unknown parameter coefficients of the generalized model equation are shown to be highly correlated to several soil properties such as moisture content, pre-compression (initial) void ratio, texture, organic matter content ans the Atterberg consistenct limits. A 3-tier classification for partition consisteny limits. A-tier claasificaton for pationing soils into groupings of response to compressive stress is proposed for soil compaction modeling. This categorization is based on soil plasticity and the existence of a “compaction threshold“ sensitivity threshold” in most soils.     

SE—Structures and Environment: Optimal Control Strategies for Carbon Dioxide Enrichment in Greenhouse Tomato Crops—Part 1: Using Pure Carbon Dioxide

Two optimal control strategies for carbon dioxide (CO₂) enrichment in greenhouse tomato crops have been developed. One uses pure CO₂ from a storage tank and the other uses CO₂ contained in the exhaust gases of boilers burning natural gas. The optimal strategies maximize the financial margin between crop value and the combined costs of the CO₂ used for enrichment and the natural gas used for heating. In this paper, the strategy for optimal control using pure CO₂ is presented and compared with strategies used by growers. The optimal strategy for enrichment with exhaust gas derived CO₂ is presented in an accompanying paper. Simulations show that at a cost of £0·09 kg⁻¹ for pure CO₂ and £0·10 m⁻³ for natural gas, the optimal enrichment strategy would increase the annual margin of crop value over CO₂ and heating costs by £4·6 m⁻² (27%) compared to a basic control strategy of enrichment to a concentration of 1000 v.p.m. (parts per million by volume) when ventilators are <5% open, otherwise enrichment to 350 v.p.m. The optimal CO₂ concentration was expressed as an algebraic function of solar radiation, wind speed and ventilator opening angle, and so enabled a quasi-optimal value to be obtained using variables measured by greenhouse environmental controllers. The quasi-optimal equation, with coefficients averaged from simulations over 4 years, gave an increased margin over the basic control strategy of £4·4 m⁻² (26%).