Thermal Band Heating for Intra-Row Weed Control

Surface steaming of soil is a very energy-intensive process, and consequently, efforts have been made to develop a machine for narrow-band steaming of the soil under and around rows of cultivated plants prior to seeding. The use of this machine may achieve up to 90% energy savings, and will also reduce the amount of damage to the flora and fauna. A special test rig has been developed with the objective of obtaining new information about narrow-band soil steaming. For a detailed analysis of the temperature profile in a cross-section of the processed band, an apparatus has been developed especially to record the temperatures obtained at 63 locations and at seven levels across the ditch. On the basis of the results from the test rig, a prototype band-steamer for field use has been developed. Tests have shown that soil temperatures exceeding 70C will be needed to protect against germination of weed seeds. For band heating such a treatment in 50 cm rows requires about 5.8 GJ/ha

Herbage intake in Danish Jersey and Danish Holstein steers on perennial ryegrass/white clover pasture

The objective of this study was to estimate herbage intake in Danish Friesian and Danish Jersey steers at an age of 8-9 months on ryegrass / white clover pasture. The steers were turned out on pasture in late April and herbage intake was estimated in June in steers of a mean live weight (± S.D.) of 264 ± 14 kg and 185 ± 25 kg for Danish Friesian and Danish Jersey respectively. Faeces and herbage samples were analysed for alkanes to estimate herbage dry matter intake, dry matter digestibility (DMD) and botanical composition of intake. The weight gains at the time of herbage intake estimation in June (kg/day) were 1.142 ± 265 kg/day and 0.927 ± 168 kg/day for Danish Friesian and Danish Jersey respectively. Daily herbage intake (kg dry matter (DM)) estimated by alkanes C32 /C33 was 8.33 ± 0.97 and 6.28 ± 0.61 per day (P<0.001) and 3.15 ± 0.32 and 3.43 ± 0.30 per 100 kg liveweight (LW) (P<0.05) for Danish Friesian and Danish Jersey respectively. The botanical composition of the diet was the same for Danish Friesian and Danish Jersey with about half of the diet being grass leaves and the other half clover leaves. It is concluded that Danish Jersey steers have higher herbage intake per 100 kg LW than Danish Friesian steers of the same age, but herbage intake per kg metabolic LW is not different between the two breeds

Modelling diverse root density dynamics and deep nitrogen uptake — a simple approach

We present a 2-D model for simulation of root density and plant nitrogen (N) uptake for crops grown in agricultural systems, based on a modification of the root density equation originally proposed by Gerwitz and Page in J Appl Ecol 11:773–781, (1974). A root system form parameter was introduced to describe the distribution of root length vertically and horizontally in the soil profile. The form parameter can vary from 0 where root density is evenly distributed through the soil profile, to 8 where practically all roots are found near the surface. The root model has other components describing root features, such as specific root length and plant N uptake kinetics. The same approach is used to distribute root length horizontally, allowing simulation of root growth and plant N uptake in row crops. The rooting depth penetration rate and depth distribution of root density were found to be the most important parameters controlling crop N uptake from deeper soil layers. The validity of the root distribution model was tested with field data for white cabbage, red beet, and leek. The model was able to simulate very different root distributions, but it was not able to simulate increasing root density with depth as seen in the experimental results for white cabbage. The model was able to simulate N depletion in different soil layers in two field studies. One included vegetable crops with very different rooting depths and the other compared effects of spring wheat and winter wheat. In both experiments variation in spring soil N availability and depth distribution was varied by the use of cover crops. This shows the model sensitivity to the form parameter value and the ability of the model to reproduce N depletion in soil layers. This work shows that the relatively simple root model developed, driven by degree days and simulated crop growth, can be used to simulate crop soil N uptake and depletion appropriately in low N input crop production systems, with a requirement of few measured parameters

Data report: electron microprobe investigation of primary minerals in basalts from the west philippine sea basin (ocean drilling program leg 195, site 1201)

The basement cored at Site 1201 (west Philippine Basin) during Ocean Drilling Program Leg 195 consists of a 91-m-thick sequence of basalts, mostly pillow lavas and perhaps one sheet lava flow, with a few intercalations of hyaloclastite and interpillow sedimentary material. Hydrothermal alteration pervasively affected the basalt sequence, giving rise to a variety of secondary minerals such as K-Fe-Mg-clay minerals, oxyhydroxides and clay minerals mixtures, natrolite group zeolites, analcite, alkali feldspar, and carbonate. The primary minerals of pillow and sheet basalts that survived the intense hydrothermal alteration were investigated by electron microprobe with the aim of characterizing their chemical composition and variability. The primary minerals are mostly plagioclase, ranging in composition from bytownite through labradorite to andesine, chromian-magnesian-diopside, and spinels, both Ti magnetite (partially maghemitized) and chromian spinel. Overall, the chemical features of the primary minerals of Site 1201 basalts correspond to the primitive character of the bulk rocks, suggesting that the parent magma of these basalts was a mafic tholeiitic magma that most likely only suffered limited fractional crystallization and crystallized at high temperatures (slightly below 1200°C) and under increasing ƒO2 conditions. The major element composition of clinopyroxene suggests a backarc affinity of the mantle source of Site 1201 basement