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The HYDRUS-2D simulation software has been used for irrigation management. Its performance under realistic irrigation regimes requires evaluation with new methodologies that integrate larger soil volumes, because soil water content is highly variable in time, space and scale. We compare direct measurements in a sloping field environment under drip irrigation with simulation using HYDRUS-2D. An advanced mobile sensor technology is used to track the dynamics of soil water content, and thus of unsaturated flow, at 0.25 m and 0.50 m depth in a field plot (6 m × 3 m; 4° slope) beneath two parallel (0.5 m separation; 7 emitters per delivery tube) dripper arrays. We document an asynchronous sequence of wetting fronts driven by the sloping surface and capture the field results well using HYDRUS-2D, in the spatial (R2 = 0.935–0.963, p

Although sticky traps are reliable indicators of pest population dynamics but pest counting by humans is time-consuming and menial labour. A novel smart vision algorithm based on two-dimensional Fourier transform (2DFT) spectrum is presented. Rather than directly counting the pests captured on the traps, the novel concept is to treat trapped pests as noise in a two-dimensional (2D) image with 2DFT serving as a specific noise collector. The research objectives included comparing human and 2DFT counting in two proof-of-principle tests: (i) simulated pests with various quantities and distributions arrayed on two series of templates using both ordered and random patterns; (ii) sweet potato whiteflies [Bemisia tabaci (Gennadius), Hemiptera: Aleyrodidae] on yellow sticky traps (YSTs) and western flower thrips [Frankliniella occidentalis (Pergande), Thysanoptera: Thripidae] on blue sticky traps (BSTs). Tests of simulated pests (2–512) on eight templates verified that the 2DFT-based index provides accurate estimates of pests captured on the traps (R2 = 1), independent of pest distribution pattern. High correlations were obtained from count results of whiteflies on 34 YSTs (R2 = 0.9994) and thrips on 33 BSTs (R2 = 0.9989). Measurement errors were addressed.

Hot vegetable oil can be used for weed control as an alternative to the use of herbicides. We analysed the temporal development of vegetable oil mineralization in soil and tested the role of nutrient supply on oil mineralization. Further, we investigated the effect of oil application on mineralization of native soil organic carbon (SOC), i.e. the priming effect. In a laboratory experiment, three oil dosages (0.1, 1.0 and 3.0ml per 35g soil) were applied to three arable soils and soil respiration was measured hourly. Both a C3-sunflower oil and a C4-corn oil were used in order to differentiate oil-derived CO2 from SOC-derived CO2. The results revealed that after 42days of incubation, 9.6 to 39.7% of the applied oil was mineralized which, however, also primed the mineralization of SOC by a factor of 2.2 to 4.2. The higher the applied oil amount, the lower was the percentage of oil-C mineralization, but the higher was the priming effect. The addition of fertilizer (0.29mgNg(-1) soil and 0.048mgPg(-1) soil) increased oil-C mineralization to 39.9 to 50.9%. We conclude that oil can temporarily accumulate in soil, especially in case of low nutrient supply. As the addition of oil stimulates SOC mineralization, a decrease of native SOC stocks may occur, which needs further quantification in long-term field experiments.

Evapotranspiration (ET) plays an important role in water and energy balance at the surface-atmosphere interface. It is widely reported that near-surface soil water content (SWC) or soil water potential (SWP) significantly affects ET and this parameter has been incorporated into the FAO Penman-Monteith (FAO-PM) model for prediction of ET during crop growth seasons. However, there is little information on the effect of SWC or SWP on prediction of ET during soil freeze-thaw cycles in winter. We present an experiment conducted at a demonstration farm with a crop of winter wheat, over two winters near Beijing, China. A lysimeter system equipped with a weather station was used to measure the ET flux and meteorological data. Unfrozen soil water content (USWC) and soil temperature (Tsoil) were measured using dielectric tube sensors (DTS) and digital temperature sensors, respectively. SWP was determined by measured USWC and a soil moisture characteristic (SMC) curve derived from the soil freezing characteristic (SFC) curve and the Clapeyron equation in frozen soil. Detailed measurements in year 1 showed that the FAO-PM model exhibited a complex error pattern, underestimating ET from unfrozen soil but overestimating ET from stable frozen soil. To address these errors, we define a freezing stress index (Ksf) as a function of SWP. Incorporation of Ksf as a modifier of the standard crop coefficient in the FAO-PM model improved prediction of ET (RMSE declined from 0.424 to 0.187 mm day−1, in year 1). These data revealed a correlation between SWP near the soil surface (

Today's agricultural engineering is characterised by automation and information technology. Automatic steering systems have become an adequate tool for guidance on a track with accuracy in the range of centimetres. Consequently, the transition from track to track must be planned exactly, so that the target track is achieved precisely. A method which can generate turn trajectories – so-called headland turns - with smooth transition and a fast computation performance is investigated. The method is based on the continuous-curvature path planning in the field of mobile robotics and is connected to the specific agronomic requirements. In this context the clothoid construction element constitutes the main construction element. It enables the smooth connection from zero curvature to maximal curvature which represents the reciprocal of the minimal turning radius. In totality, a manoeuvre can be planned with modified Dubins curves, both going backwards and forwards is feasible with modified Reeds and Shepp curves. Seven different manoeuvres are useful from an agronomic point of view. It is shown that all turn manoeuvres are feasible with this method. Also an analysis regarding the trajectory length, the headland width and the operation time is shown.

To ensure penetration results that are comparable under various experimental conditions, cone penetrometers specified by ASABE Standards have been suggested for many years. Elastic-plastic properties are typical of most agricultural materials, so the material being penetrated by a cone penetrometer may contact the penetrometer shaft, and friction on the shaft may affect the penetration force data. Development of a method for quantifying this friction force is expected to improve the accuracy of cone penetrometer data. The objectives of this study were: (1) to evaluate a method for determining friction force on the shaft of a cone penetrometer while penetrating sand and clay soils packed in a specific cylinder, (2) to verify the penetration friction component (PFC) that may significantly influence penetration resistance (PR) measurements for various densities of chopped maize, and (3) to assess the effectiveness of a proposed filter method for adjusting friction on the penetrometer shaft. With these intentions, we embedded strain gauges into an ASABE Standard small cone. The tip was free from the shaft friction, so the output of this sensor was used as a reference in this study. We found the ASABE Standard small cone suitable for a broad range of soil textures, as little PFC was observed from the sand or the clay soil samples. However, considerable friction from penetrating chopped maize was observed at three levels of packed density using the cylinder method. In this situation, with the reference of the sensor output inside the tip, a pair of coefficients (C 1 = 2329, C 2 = 2120) were optimized to filter the PFC out of the PR measurement. The adjusted data agreed well with those of the reference sensor (R 2 = 0.968; RMSE = 6.521 N). Thus, ASABE Standard penetrometers can also be used for silage materials without mechanical modification.

Precision-farming applications are mainly based on site-specific information of soil properties at the field scale. For this purpose, a number of novel sensor techniques have been developed but not intensively tested under different field conditions. This study presents a combined application of a self-developed dual-sensor vertical penetrometer (DVP) for measuring volumetric soil water content (VSWC) and cone index (CI), and an EM38 for soil apparent electrical conductivity (ECa) in a pasture (1.4 ha). To verify the feasibility of the DVP for interpreting the depth-specific information in the field, not only the soil physical properties and their geographical coordinates were measured, but also geo-referenced yield data were collected. We found that the yield pattern was quite similar to the soil water-content pattern of each layer (layer-1: 5–15 cm; layer-2: 15–25 cm, layer-3: 25–35 cm) and ECa pattern. Using the map-based comparisons in conjunction with the statistical analyses, the effect of each measured soil physical property (VSWC, CI, and ECa) on the yield was investigated. The regression between the yield and VSWC at each layer fitted a quadratic equation (R2 = 0.515 at 5–15 cm; R2 = 0.623, at 15–25 cm; R2 = 0.406 at 25–35 cm). The negative correlation between yield and CI at each layer fitted a linear model with R2 ≥ 0.510.

Topsoil porosity (TSP) is an important parameter for the research of soil physics, agriculture and environmental protection. However, the traditional method for measuring porosity is time consuming. Conversely, a series of new methods measuring soil surface roughness (SSR) are increased and become more and more quickly. Some researchers propose to predict TSP by SSR. In this study, two fields cultivated by different tillage type were investigated under natural condition during four years (2006-2009). The results of this study show that (i) both of soil roughness and porosity are decreased over time; (ii) there are strong correlation between soil porosity and roughness effected by rainfall; (iii) after introduce the index of accumulative mean rainfall (AMR), a model of multiple linear regression for presenting the correlation among SSR, TSP and rainfall was built using sampling data of 2006-2009 with R2>0.7.

A direct injection system that injects pesticides locally at all nozzles on a boom was assembled and investigated under laboratory conditions with regards to its ability to be cleaned. The system was contaminated with a safe-to-use polyvinylpyrrolidone-water solution as a test pesticide before cleaning. The cleaning process was divided into two steps: 1) reclaiming the simulated pesticide by pushing it back into the pesticide tank using pressurised air (pre-cleaning) and 2) rinsing the contaminated part of the hydraulic system with water. Cleaning performance was investigated systematically to ascertain the initial dynamics of the rinsing process as well as long term cleaning. Evaluations included variation of 1) pre-cleaning time and 2) water inlet position. Measurements showed that the concentration of the simulated pesticide in the rinsing water could initially be as high as 30%. As the pre-cleaning time was extended the initial concentration was reduced by one third. Changing the water inlet position reduced the initial concentration of the simulated pesticide in the rinsing water to 5%. These concentrations were much higher than in most common spray solutions. This means that if an active pesticide was used further dilution of the pesticide concentration in the rinsing water would be required for it to be sprayed on a crop. In some cases it took more than 10 min to dilute simulated pesticide residues in a 3 m test section down to 0% which clearly shows the need for more research on factors influencing the cleaning process and more development of cleaning processes.

A combined penetrometer is an appropriate tool to measure the soil cone resistance and the water-content profile. As a relatively new technique, a combined capacitance-penetrometer for the simultaneous measurement of cone index and soil water content was developed at the Department of Agricultural Engineering of Bonn University in 2002. The objective of this study was the evaluation of the effectiveness and applicability of the innovated penetrometer with a focus on three aspects: (1) A capacitance sensor with two electrode configurations was calibrated for silt loam, sandy loam, and sand. The calibration results show that both electrode configurations have sufficient water-content sensitivity, but soil-specific calibrations seem necessary. (2) Under laboratory conditions, the dynamic resolution and response of the capacitance-penetrometer were validated, and its radius of influence was determined. (3) The field measurement results demonstrate that this measurement technique can be used to improve the interpretation quality of soil cone index data. Bewertung eines Penetrometers zur gleichzeitigen Bestimmung von Eindringwiderstand und Bodenfeuchte Fur die Ermittlung von Bodenprofilen fur den Eindringwiderstand und die Bodenfeuchte erscheint die Kombination aus Penetrometer und Bodenfeuchtesensor als geeignete Losung. Ein solcher Kombinationssensor wurde im Jahr 2002 am Institut fur Landtechnik der Universitat Bonn fur die simultane Messung des Eindringwiderstandes und der Bodenfeuchte entwickelt. In diesem Beitrag wird die Tauglichkeit und Anwendbarkeit fur Feldmessungen in folgenden Schritten dargestellt: (1) Ein kapazitiver Sensor mit zwei Elektrodenkonfigurationen wurde fur die drei Bodenarten schluffiger Lehm, sandiger Lehm und Sand kalibiriert. Die Kalibrationsgleichungen zeigen, dass beide Elektrodenanordnungen uber ausreichende Empfindlichkeit zur Bodenfeuchtemessung verfugen. Es sind aber bodenartspezifische Kalibrierungen notwendig. (2) Die dynamische Auflosung und das Ansprechverhalten des Feuchtesensors wurden fur beide Elektrodenanordnungen untersucht, und die Ausbreitung des dielektrischen Feldes wurde bestimmt. (3) Die Ergebnisse der Messungen im gewachsenen Boden zeigen, dass die Messmethode zur Verbesserung der Interpretation der Konus-Indexwerte herangezogen werden kann.