A model of decision-making and information flows for information-intensive agriculture

This paper describes the development of a systems based model to characterise farmers’ decision-making process in information-intensive practices, and its evaluation in the context of Precision Agriculture (PA). A participative methodology was developed in which farm managers decomposed their process of decision-making into brief decision statements along with associated information requirements. The methodology was first developed on a university research farm in Denmark and further revised during testing on a number of research and commercial farms in Indiana, USA. Twenty-one decision-analysis factors were identified to characterise a farm manager’s decision-making process. Then, a general data flow diagram (DFD) was constructed that describes the information flows “from data to decision”. Illustrative examples of the model in the form of DFDs are presented for a strategic, a tactical and an operational decision. The model was validated for a range of decisions related to operations by three university farm managers and by five commercial farmers practicing PA for cereal, corn and soybean production in Denmark and in Indiana, USA.     

Effect of irrigation on tillering in wheat,triticale and barley in a water-limited environment

Summary The effect of irrigation on tillering and tiller mortality in varieties of wheat (Triticum aestivum and T. durum), triticale and barley was studied under field conditions. Low temperature in the early stages of growth promoted production of tillers whereas increase in temperature during extension growth phase increased tiller mortality. More than 1000 tillers m^–2 were produced with five irrigations but 40% or more died. With limited water availability tiller production was reduced but so was their mortality. Grain yield in wheat and triticale was positively correlated with productive tillers and negatively correlated with the maximum number of tillers produced in wheat and barley grown under limited irrigation conditions. Varieties with a capacity to produce fewer tillers were identified. Some of them proved more stable in yield. No correlation was found between tiller number and grain yield in the frequently irrigated treatment.     

农林废弃物超低酸水解装置及试验研究

自行设计了木质纤维素类生物质超低酸水解装置,该装置可以间歇进料方式实现生物质的超低酸水解。在该装置上分别以木聚糖和定量滤纸为模化物得到了半纤维素和纤维素水解的最佳工况,进而对白松、速生杨和玉米秸秆这三种在我国分布较为广泛的原料进行了超低酸两步水解研究,分别得到了51.24%、78.27%和84.10%的可水解原料转化率和48.19%、57.96%和37.48%总还原糖得率,并以GCMS定性还原糖外的其他产物,最后对水解残渣做了分析研究。     

Determining transpiration from meteorological data and crop characteristics for irrigation management

Summary Traditional meteorological estimates of evapotranspiration include empirical crop factors which are inadequate for scheduling high frequency irrigation. The performance of a transpiration model was tested and adapted to suit the operational requirements of automated irrigation systems. Hourly measurements of global solar radiation, air temperature, humidity and wind speed, obtained from an automatic weather station are inputs to the model. Additional inputs include daily updated data of plant height and leaf area index. This information is processed to determine the active coupling surface between the crop and the atmosphere. The model takes into account the resistance of the leaf to diffusion of water vapor.Calculated transpiration, based on the model, matched very closely measurements of latent heat flux in an irrigated cotton field. It was also in good agreement with water uptake measured in stems of the cotton plants using a heat pulse technique. The test also showed that implementation of the model in the field under study would have improved the efficiency of water application.Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel, No. 1855-E, 1986 series     

Design and evaluation of an irrigation system for creating water gradients under an automatic rain shelter

Summary This paper reports on the design and performance of an irrigation system associated with a rain shelter. The shelter is used in the closed position as a platform for multiple spray lines. This system automatically supplies, at a specified time, water of specified depth and delivery rate, either uniformly or on a specified gradient across the sheltered area. Variations in crop water deficits and yields have conformed closely to imposed water gradients.     

Determination of soil water content by X-ray computed tomography and magnetic resonance imaging

Summary Experiments were conducted to compare the use of X-ray computed tomography (CT) and magnetic resonance imaging (MRI) methods for determining water content in soil. Soil cores of Mexico silt loam packed at bulk densities of 1.2, 1.3, 1.4, and 1.5 Mg/m³ and Crider silty clay packed at bulk densities of 1.3, 1.4, 1.5, and 1.6 Mg/m³ were evaluated using a CT scanner. Results indicate that the X-ray CT explained 98% of the variation in water content over a range from air-dry to saturation. Three attempts were made to obtain MRI scans of soil cores varying in soil water content. Two of these attempts were made with contrasting agents. No images were obtained of the soil cores during all three attempts. It is suggested that the failure to obtain images of soil cores is closely related to the settings of the pulse repetition time and the spin echo time on the MRI unit. The range in settings for these two parameters on the commercial MRI unit used in this study did not allow short increments to be selected and therefore it was not possible to obtain reconstructed images of the soil cores for this experiment. However accessibility to a prototype MRI unit should allow more conclusive work to determine the full capabilities of MRI for determining soil water content.Contribution from the Missouri Agricultural Experiment Station Journal No. 10424, Department of Agronomy, University of Missouri, Columbia, MO 65211, USA     

Irrigation scheduling effects on yield and phosphorus uptake of cowpea

A line-source sprinkler irrigation system was used for irrigation-fertilizer cowpea (Vigna unguiculata [L.] Walp.) production studies. The relative merits and demerits of irrigating frequently but with smaller amounts of water than the design water application depth as compared to stage-of-growth and normal interval irrigation were investigated with five levels of fertilizer P, three water levels and five irrigation schedules.Dry matter production on the basis of forage produced was used as the yield indicator. The plants were harvested when the more advanced individuals reached the late boot stage immediately preceding the appearance of their inflorescences. P uptake was also measured.Statistical analyses of yield and P uptake gave a positive response of the crop to added fertilizer and irrigation water. Application of 70 kg/ha P₂O₅ produced the highest yields under all irrigation schedules. Irrigating too frequently was found to be detrimental; maximum yield under P fertilization was obtained with irrigations scheduled at half the design interval and with half the design irrigation depth. Uptake of P increased with yield.     

A logistic analysis of the factors determining the decision of smallholder farmers to intercrop: A case study involving rubber–tea intercropping in Sri Lanka

The factors influencing the decision of smallholder farmers to adopt new farming technologies were studied with reference to rubber–tea intercropping in Sri Lanka. Rubber–tea intercropping has been recommended previously to rubber farmers as a means to improve productivity and income during the early pre-tapping phase of rubber growth. Although crop trials have shown that the two crops are agronomically compatible and potentially produce a combined economic yield superior to the yield of a sole crop grown on the same area of land, there is little evidence of widespread adoption of this practice among smallholder farmers in Sri Lanka. The aim of the study was to determine the major factors that influence the decision to undertake rubber–tea intercropping and to construct a predictive model that describes the likelihood of adoption of intercropping by traditional smallholder rubber growers. A rapid rural appraisal (RRA) was undertaken based on semi-structured interviews of 90 smallholder farmers in the main rubber growing low wet zone of Sri Lanka. Among a number of factors shown to significantly influence the decision to intercrop tea with rubber, three were shown to operate independently, namely level of income, source of income (i.e. solely from own farm or from farm plus additional off-farm enterprises), and availability of land considered suitable for tea cultivation. A statistical model developed through correlation and logistic analysis, which predicts the likelihood of a smallholder adopting intercropping based on these factors, is presented and discussed. The most likely combination of circumstances (82% probability) under which rubber–tea intercropping is practiced is shown to be where the farmer’s income is greater than Rs. 10,000 per month, where the farmer’s income is based solely on own farm enterprises, and where more than 80% of the farmer’s land area was judged to be suitable for tea cultivation. Conversely, 30% of smallholder farmers that chose not to intercrop did possess land suitable for tea cultivation. Qualitative responses to the RRA indicated that limitation of technical knowledge was the main problem subsequently faced by rubber farmers who had adopted rubber–tea intercropping. Results indicate that there is need for both income support through farm subsidies and further agricultural extension services, if rubber–tea intercropping is to be adopted more widely in Sri Lanka. The wider usefulness of the developed logistic model in determining the likelihood of adoption of intercropping by smallholder farmers is discussed.     

介电种子分选机工况参数的选择

以油菜种子的介电分选试验为基础,分析了分选电压、滚筒转速和喂入量对获选种子净度、千粒质量以及质量比例的影响规律,为介电种子分选机工况参数的选择提供了参考。     

Impact of crop rotation and minimum tillage on water use efficiency of irrigated cotton in a Vertisol

Crop water use efficiency of irrigated cotton was hypothesized to be improved by a combination of minimum tillage and sowing a wheat (Triticum aestivum L.) rotation crop. This hypothesis was evaluated in a Vertisol near Narrabri, Australia from 1997 to 2003. The experimental treatments were: continuous cotton sown after conventional or minimum tillage and minimum-tilled cotton–wheat. Soil water content was measured with a neutron moisture meter, and runoff with trapezoidal flumes. Application efficiency of irrigation water was estimated as the amount of infiltrated water/total amount applied. Plant available water was estimated using the maximum and minimum soil water storage during the growing season. Evapotranspiration was estimated with the water balance method using measured and simulated soil water data. Seasonal evapotranspiration was partitioned into that coming from rainfall, irrigation and stored soil water. Crop water use efficiency was calculated as cotton lint yield per hectare/seasonal evapotranspiration. Rotation of cotton with wheat and minimum tillage improved water use efficiency in some years and application efficiency in all years. Average seasonal evapotranspiration was higher with minimum tillage than with conventional tillage. In years when cotton was sown in all plots, average cotton crop water use efficiencies were 0.23, 0.23 and 0.22 kg (lint)/m³ for minimum-tilled cotton–wheat and continuous cotton, and conventionally tilled continuous cotton, respectively. In-season rainfall efficiency, transpiration and soil evaporation were unaffected by cropping system.