Rules of thumb for minimizing subsoil compaction

Subsoil compaction is persistent and can affect important soil functions including soil productivity. The aim of this study was to develop recommendations on how to avoid subsoil compaction for soils exposed to traffic by machinery at field capacity. We measured the vertical stress in the tyre–soil contact area for two traction tyres at ca. 30‐ and 60‐kN wheel loads on a loamy sand at field capacity. Data on resulting stress distributions were combined with those from the literature for five implement tyres tested at a range of inflation pressures and wheel loads. The vertical stress in the soil profile was then predicted using the Söhne model for all tests in the combined data set. The predicted stress at 20 cm depth correlated with the maximum stress in the contact area, tyre inflation pressure, tyre–soil contact area and mean ground pressure. At 100 cm depth, the predicted vertical stress was primarily determined by wheel load, but an effect of the other factors was also detected. Based on published recommendations for allowable stresses in the soil profile, we propose the ‘50‐50 rule’: At water contents around field capacity, traffic on agricultural soil should not exert vertical stresses in excess of 50 kPa at depths >50 cm. Our combined data provide the basis for the ‘8‐8 rule’: The depth of the 50‐kPa stress isobar increases by 8 cm for each additional tonne increase in wheel load and by 8 cm for each doubling of the tyre inflation pressure. We suggest that farmers use this simple rule for evaluating the sustainability of any planned traffic over moist soil.     

Molar absorptivities and reducing capacity of pyranoanthocyanins and other anthocyanins

To improve accuracy in the determination of anthocyanin purity and succeeding antioxidant capacity, 1H and 13C nuclear magnetic resonance spectroscopy have been combined with high-performance liquid chromatography (HPLC) equipped with a diode array detector and UV-vis spectroscopy in the analysis of anthocyanidin 3-glycosides and 5-carboxypyranoanthocyanidin 3-glycosides. The molar absoptivity (epsilon) values were found to be relatively similar, in contrast to previously reported literature values, and the average epsilon values for both anthocyanidin 3-monoglycosides and 5-carboxypyranoanthocyanidin 3-glycosides were proposed to be 22,000 and 23,000 in acidified aqueous and methanolic solutions, respectively. To assess the influence of structure on the potential antioxidant capacity of anthocyanins, the 3-glucosides of pelargonidin (1), cyanidin (2), peonidin (3), delphinidin (4), petunidin (5), malvidin (6), 5-carboxypyranopelargonidin (8), 5-carboxypyranocyanidin (9), 5-carboxypyranodelphinidin (11), 5-carboxypyranopetunidin (12), and 5-carboxypyranomalvidin (13) and the 3-galactosides of cyanidin (7) and 5-carboxypyranocyanidin (14) were examined by a ferric ion reducing antioxidant power (FRAP) assay. The reducing capacities of the individual anthocyanins were in the range of 0.9-5.2 micromol of Trolox equivalents/micromol. The two 5-carboxypyranoanthocyanins 11 and 9 and the four common anthocyanins 2, 4, 7, and 14, all possessing pyrogallol or catechol type of B rings, showed the highest antioxidant capacity measured by FRAP. However, the inclusion of the 5-hydroxyl in the D ring and just one oxygen substituent on the B ring in 8 diminished the reducing capacity considerably. Correspondingly, electrochemical behavior of 5-carboxypyranoanthocyanidin 3-glucosides and anthocyanidin 3-glucosides was derived using HPLC coupled to a coulometric array detector set from 100 to 800 mV in increments of 100 mV. The relative order of the reducing capacity of the various 5-carboxypyranoanthocyanidin 3-glucosides and anthocyanidin 3-glucosides were nearly alike, whether determined by coulometric array detection or FRAP.     

Starter fertilizer to spring barley and spring wheat in south-east Norway: Effects on growth and nutrient uptake

Abstract

Field experiments were carried out on three representative soils, to evaluate the effect of various starter fertilizers, together with different rates of band placed phosphorus (P), on nutrient uptake and yield of spring barley (Hordeum vulgare L.) and spring wheat (Triticum aestivum L.). The starter fertilizers were placed in the immediate vicinity of the seed, while the band placed P was placed at about 5 cm below the seeds and spaced at 25 cm between alternate seed rows. As starter fertilizer, monoammonium phosphate (MAP), calcium nitrate (CAN), ammonium nitrate (AN) and triple superphosphate (P20) were compared. In both species, effects of starter fertilizer on P uptake were most marked early in the growing season. At GS 13 application of 20 kg P ha^?1 as MAP increased the P uptake by 50% in barley and by 35% in wheat, compared to no seed-placed nutrients. For grain, the increase in P content was 8% for both species. The higher P uptake at GS 13 was supported by observations of higher plant vigour in the treatments with either P20 or MAP as starter fertilizer. The use of N only as starter fertilizer did not increase the vigour of the plants. Band placement of P also gave more vigorous plants in spring barley. The grain yield increased on the silty clay loam and on the silt soil when starter fertilizer was applied, especially with the use of MAP. Smaller and non-significant yield differences were found when starter fertilizer was used on the loam soil. No delay or reduction of emergence was observed with starter fertilizer. Therefore, on soils where root growth or nutrient uptake becomes limited during the first weeks after sowing, application of starter fertilizer is recommended in Norway for both spring barley and spring wheat. Crops grown on silty soils seem to have an especially high demand for easily available P given as starter fertilizer.     

Effect of developmental stage on carbohydrate accumulation patterns during winter of timothy and perennial ryegrass

Abstract

Changes in non-structural carbohydrates before and during winter are one of the major plant responses to winter stress. However, the observed pattern of changes is variable, not only between grass species but also between different experiments. This study examined the effect of developmental stage on carbohydrate reserves during winter in two grass species differing in winter hardiness.

Timothy (Phleum pratense L.) and perennial ryegrass (Lolium perenne L.), sown early or late in the growing season, were sampled for total non-structural carbohydrates (TNC) in late October (end of main growing season), and then in late January, early March and late April. Quantitative and qualitative patterns of carbohydrate accumulation in crown segments were influenced both by plant genotype and developmental stage of the plants prior to winter. TNC increased from October to March, demonstrating considerable cell activity during winter, and declined to their lowest level in April. Sucrose proved to be the major reserve carbohydrate, followed by fructans. The highest content of TNC was found in the most winter-hardy cultivars, particularly in January and March. Early-sown plants accumulated higher levels of fructans than of sucrose, whereas late-sown plants mainly accumulated sucrose. These differences persisted during the winter. It can be concluded that the pattern of carbohydrate accumulation during winter differed between the two species studied and it was strongly affected by both cultivar and plant-developmental stage.     

Scale-dependent importance of environment, land use and landscape structure for species richness and composition of SE Norwegian modern agricultural landscapes

Knowledge of variation in vascular plant species richness and species composition in modern agricultural landscapes is important for appropriate biodiversity management. From species lists for 2201 land-type patches in 16 1-km² plots five data sets differing in sampling-unit size from patch to plot were prepared. Variation in each data set was partitioned into seven sources: patch geometry, patch type, geographic location, plot affiliation, habitat diversity, ecological factors, and land-use intensity. Patch species richness was highly predictable (75% of variance explained) by patch area, within-patch heterogeneity and patch type. Plot species richness was, however, not predictable by any explanatory variable, most likely because all studied landscapes contained all main patch types – ploughed land, woodland, grassland and other open land – and hence had a large core of common species. Patch species composition was explained by variation along major environmental complex gradients but appeared nested to lower degrees in modern than in traditional agricultural landscapes because species-poor parts of the landscape do not contain well-defined subsets of the species pool of species-rich parts. Variation in species composition was scale dependent because the relative importance of specific complex gradients changed with increasing sampling-unit size, and because the amount of randomness in data sets decreased with increasing sampling-unit size. Our results indicate that broad landscape structural changes will have consequences for landscape-scale species richness that are hard or impossible to predict by simple surrogate variables.     

A Micro‐Simulation Approach to Modelling Spatial Unemployment Disparities

This paper aims to construct a comprehensive model capable of simulating spatial unemployment disparities. The key feature of the model is that it simultaneously deals with commuting and migration. Much of the existing literature simply models one adjustment mechanism at a time. This paper adopts a micro‐simulation approach to build a model which can deal with equilibrium and disequilibrium unemployment disparities in a context where commuting and migration are possible. The model is then used to demonstrate the importance of considering both types of flows and to guide future empirical and theoretical work in the area.     

Increased dietary phosphorous prevents vertebral deformities in triploid Atlantic salmon (Salmo salar L.)

Triplicate groups of triploid and diploid Atlantic salmon were fed diets with a low (LP, total P: 7.1 g kg^?1), medium (MP, total P: 9.4 g kg^?1) or high (HP, total P: 16.3 g kg^?1) phosphorous (P) level from first feeding (0.18 g) to transfer to sea water (~50 g, duration: 203 days) and subsequently fed a commercial diet in sea water for 426 days (~3 kg). This study examined the short‐ and long‐term effects of dietary P on freshwater performance (mortality, growth), vertebral deformities (radiology), bone cell activity (ALP and TRACP enzyme activity in vertebrae and scales, and fgf23, bgp and igf‐I relative gene expression in vertebrae), bone mineralization (ash content) and some parameters related to fish condition (heart and liver size). Irrespective of ploidy, at seawater transfer, fish fed the MP diet had significantly highest length and weight and those fed the LP diet significantly lowest length and weight, while those fed the HP diet had intermediate lengths and weights. Increased dietary phosphorus reduced deformities in both ploidies at seawater transfer; however, triploids fed the LP and MP diets had more deformities than diploids fed the respective diets, while there was no ploidy effect observed for fish fed the HP diet. The vertebral bone ash content at seawater transfer was significantly higher in diploids than in triploids when fed the MP diet only. Alkaline phosphatase (ALP) and tartrate‐resistant acid phosphatase (TRACP) enzyme activities and relative gene expression of bone hormones involved in metabolism of plasma phosphate (fgf23) and bone growth (bgp) were not affected by ploidy at seawater transfer, but by dietary P level; LP increased ALP activity and reduced TRACP activity and fgf23 and bgp expression levels in vertebral bone. In scales, LP increased both ALP and TRACP activity. At the termination of the seawater period, the group‐wise pattern in occurrence of vertebral deformities was the same as at seawater transfer. The present results on mortality, growth, bone mineralization and development of skeletal deformities all demonstrate that triploids have a higher P requirement than diploids in fresh water. This study shows that an optimalization of P nutrition for triploid Atlantic salmon can improve health and welfare and reduce down‐grading of triploid salmon.     

Phytase and sodium diformate supplementation in a plant‐based diet improves protein and mineral utilization in rainbow trout (Oncorhynchus mykiss)

A basal isonitrogenous and isoenergetic plant‐based diet (Control) was supplemented with either 10 g kg^?1 sodium diformate (NaDF), 4000 FTU kg^?1 phytase (Phy) or a combination of both additives (NaDF + Phy). Three hundred juvenile rainbow trout with an average weight of 120 g were randomly distributed into 12 fibreglass tanks (300 L). After 65 days of trial, fish fed diets containing phytase, NaDF or the combination of both additives showed a higher growth rate (P < 0.05) compared to fish fed Control diet. NaDF increased feed intake (P = 0.032), while phytase inclusion resulted in a better feed conversion ratio (P < 0.0001) and a higher N retention efficiency (P = 0.02) compared with the Control. Apparent digestibility of P, Ca, Mg and Zn was improved by the use of phytase (P < 0.005) as well as P, Ca and Mg retention efficiency in fish (P < 0.0001). Using 4000 FTU kg^?1 phytase in plant‐based diets resulted in a 13% and 50% reduction in N and P loadings, respectively. The use of NaDF in combination with phytase in a plant‐based diet for rainbow trout resulted in a higher weight gain than that when NaDF was used alone.