Statistical aspects of experimental designs implemented in designs

The report describes the statistical aspects of experimental designs used in an project

Root growth and soil nitrogen depletion by onion, lettuce, early cabbage and carrot

Experiments examining root growth, the utilization of N and the effect of green manures were carried out on four vegetable crops. Large differences were observed both in rooting depth penetration rates, and in final rooting depth and distribution. Onion had a very low depth penetration rate, carrot an intermediate rate, and lettuce and cabbage showed high rates. A combination of depth penetration rates and duration of growth determined rooting depth at harvest. Therefore, lettuce, which had a very short growing season, had a shallow root system at harvest, whereas carrot with a lower depth penetration rate but a long growing season had deep rooting at harvest. The final rooting depth of the vegetables varied from approximately 0.3 m for onion to more than 1.0 m for carrot and early cabbage. Carrot and cabbage were able to utilize N from deeper soil layers, not available to onion and lettuce. The ability of green manure crops to concentrate available N in the upper soil layers was especially valuable when they were grown before the two shallow rooted crops

Effect of crop management practices on the sustainability and environmental impact of organic and low input food production systems

While organic farming can reduce many of the environmental problems caused by agriculture, organic farming also includes some practices which are questionable in terms of environmental effects. Organic farming practices (rotations, fertilisation regimes, cover crop use) can differ significantly and this leads to large differences in its environmental effects. This leaves considerable scope to improve the environmental effects of organic farming. The environmental aspects of organic farming are discussed, and model simulations are used to illustrate how even moderate changes in organic rotations can have large effects on sustainability, here measured by a simple index of nitrogen lost by leaching relative to nitrogen harvested by the crops. In WP3.3.4 we are working to improve model simulation of organic rotations, and in WP7.1 we are making environmental assessment of organic cropping practices tested in the QLIF project, using model simulations and other approaches

Utilising differences in rooting depth to design vegetable crop rotations with high nitrogen use efficiency (NUE)

A number of methods involving plant or soil analysis or modelling have been developed to optimise N fertilization of vegetable crops. The methods aim at improving the NUE of each single crop, but do not really consider the crop rotation as such. Various measures can be used to increase the NUE of the crop rotation; measures that can be combined with the methods aimed at optimising NUE of each single crop. The aims of the paper are to discuss the methods for optimising NUE at the crop rotation level and to present examples of how this can be done. The main methods discussed are 1) how can crops with different rooting depth be optimally placed in a cropping sequence and 2) how can catch crops be introduced to optimise NUE. Results show that if N left in the soil after harvest on one crop is retained in the soil until spring, it will normally be found in deeper soil layers. Therefore rooting depth of the vegetable crops is important. It is illustrated that by placing deep-rooted crops in the crop rotation preferentially where much N was left in the soil in the previous year can strongly increase the utilisation of the N residues. It is also shown how catch crops can be used to maintain a high NUE, especially in situations where the farmers choose to grow shallow-rooted vegetables even though much N may be available in deeper soil layers

Incomplete split-plots in variety trials - based on a-designs

Incomplete split-plots based on a-designs are proposed as alternative to traditional split-plot designs. The purpose of the incomplete split-plot designs is to increase the efficiency of the treatment (whole plot factor) comparisons especially for specific varieties. The designs are constructed in 4 different methods, but in all methods the unit for the treatments are the incomplete blocks (in stead of whole plots with all varieties in traditional split-plots). The designs are compared with each other and with traditional split-plot and randomised complete block designs using generated data with known covariance structure and using data from 5 uniformity trials. The comparisons showed that these designs in almost all cases were more efficient than the traditional designs and that they were never considerably less efficient that these. Designs where the incomplete blocks are grouped so that each group contain all treatments (one incomplete block with each treatment) were more efficient that when the incomplete blocks were randomised independently (in one step)

Effects of vertical distribution of soil inorganic nitrogen on root growth and subsequent nitrogen uptake by field vegetable crops

Information is needed about root growth and N uptake of crops under different soil conditions to increase nitrogen use efficiency in horticultural production. The purpose of this study was to investigate if differences in vertical distribution of soil nitrogen (Ninorg) affected root growth and N uptake of a variety of horticultural crops. Two field experiments were performed each over 2 years with shallow or deep placement of soil Ninorg obtained by management of cover crops. Vegetable crops of leek, potato, Chinese cabbage, beetroot, summer squash and white cabbage reached root depths of 0.5, 0.7, 1.3, 1.9, 1.9 and more than 2.4 m, respectively, at harvest, and showed rates of root depth penetration from 0.2 to 1.5 mm day)1 C)1. Shallow placement of soil Ninorg resulted in greater N uptake in the shallow-rooted leek and potato. Deep placement of soil Ninorg resulted in greater rates of root depth penetration in the deep-rooted Chinese cabbage, summer squash and white cabbage, which increased their depth by 0.2–0.4 m. The root frequency was decreased in shallow soil layers (white cabbage) and increased in deep soil layers (Chinese cabbage, summer squash and white cabbage). The influence of vertical distribution of soil Ninorg on root distribution and capacity for depletion of soil Ninorg was much less than the effect of inherent differences between species. Thus, knowledge about differences in root growth between species should be used when designing crop rotations with high N use efficiency

Hay production in North Europa

Hay feeding might have some advantaged in relation to herd health and reduces the risk for contamination of the milk with spores. Hay production compared to silage is more resource intensive – like use of energy for drying. Hay from two types of herb enriched grass swards and the traditional grassland showed no difference in intake or milk production when compared at three organic farms. Feed efficiency tended to be lower than standards based on silage feeding

Impact of foliar diseases in organically grown barley: Influence of fertilization, nutrient content in leaves, varietal disease resistance characteristics and yield potential

Significant increase in severity of powdery mildew,leaf rust and net blotch with increasing N-content in plant leaves 30 days after germination (all years where the relevant diseases were present at a substantial level). This may explain: · Most of the environmental main effects (field) on disease. · Effect of treatments, i.e., treament 4 resulted in reduced N/increased K content in leaves, which coincided with reduced levels of disease. We observed no clear effect of P, Ca, S, and Zn content in leaves on disease. Micronutrients as Cu, Mo and Mn showed significant effects on powdery mildew in one year but not the other; further interpretation may not be possible due to inter-correlation among the effect of micro-nutrients. The diseases had a significant yield reducing effect, in particular powdery mildew and net blotch, which occurred at highest severities. In addition, net blotch affected root development, resulting in significant shorter roots, whereas powdery mildew did not. The effect of disease on root length was of the same order of magnitude as the factor 'variety', but larger than effects of 'year'

A decision support model simulating the vitamin supply over the year on a farm

The aim of this new project is to develop a prototype of a decision support model simulating the feed and vitamin supply during a year to different groups of animals (calves, heifers, dry cows, cows in early and late lactation) on a farm self-sufficient with feed. The model takes into account that the content of vitamin depends on choice of crops, utilization method, cutting date, conservation method and duration of storage together with traditional optimizing the feed-ing scheme

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