Margrethe Askegaard

Design of an Organic Farming Crop-Rotation Experiment

A field experiment is being conducted which focuses on crop rotations for cereal production in organic farming. The objective of the experiment is to explore the possibilities for both short-term and long-term increases in organic cereal production through manipulation of crop-rotation design on different soil types. This paper describes the design of a rather complex experiment, and later papers will describe and discuss the results. Three factors are included in the experiment in a factorial design with two replicates: (1) fraction of grass-clover and pulses in the rotation (crop rotation); (2) catch crop (with or without catch crop or bi-cropped clover); and (3) manure (with or without animal manure applied as slurry). All fields in all rotations are represented in each year. The experimental factors are defined to allow management to be adjusted for optimization of the individual treatment combinations. This makes the systems more realistic and the results more applicable in practical farming. The experiment is being conducted at four locations representing major soil types and climate regions in Denmark. The main design criteria are related to requirements for a long-term experiment and the need for performing studies and experiments within the experiment itself.

Multielemental Fingerprinting as a Tool for Authentication of Organic Wheat, Barley, Faba Bean, and Potato

The multielemental composition of organic and conventional winter wheat, spring barley, faba bean, and potato was analyzed with inductively coupled plasma-optical emission spectrometry (ICP-OES) and -mass spectrometry (ICP-MS). The crops were cultivated in two years at three geographically different field locations, each accommodating one conventional and two organic cropping systems. The conventional system produced the highest harvest yields for all crops except the nitrogen-fixing faba bean, whereas the dry matter content of each crop was similar across systems. No systematic differences between organic and conventional crops were found in the content of essential plant nutrients when statistically analyzed individually. However, chemometric analysis of multielemental fingerprints comprising up to 14 elements allowed discrimination. The discrimination power was further enhanced by analysis of up to 25 elements derived from semiquantitative ICP-MS. It is concluded that multielemental fingerprinting with semiquantitative ICP-MS and chemometrics has the potential to enable authentication of organic crops.

Whole-rotation dry matter and nitrogen grain yields from the first course of an organic farming crop rotation experiment

The possibilities for increasing total grain yield in organic cereal production through manipulation of crop rotation design were investigated in a field experiment on different soil types in Denmark from 1997 to 2000. Three experimental factors were included in the experiment in a factorial design: 1) proportion of grass-clover and pulses in the rotation, 2) catch crop (with and without), and 3) manure (with and without). Three four-course rotations were compared. Two of the rotations had one year of grass-clover as a green manure crop, either followed by spring wheat or by winter wheat. The grass-clover was replaced by winter cereals in the third rotation. Animal manure was applied as slurry in rates corresponding to 40% of the nitrogen (N) demand of the cereal crops. Rotational grain yields of the cereal and pulse crops were calculated by summing yields for each plot over the four years in the rotation. The rotational yields were affected by all experimental factors (rotation, manure and catch crop). However, the largest effects on both dry matter and N yields were caused by differences between sites caused by differences in soils, climate and cropping history. The rotation without a green manure crop produced the greatest total yield. Dry matter and N yields in this rotation were about 10% higher than in the rotation with a grass-clover ley in one year of four. Therefore, the yield benefits from the grass-clover ley could not compensate for the yield reduction as a result of leaving 25% of the rotation out of production. There were no differences in dry matter and N yields in grains between the rotations, where either spring or winter cereals followed the grass-clover ley. The N use efficiency for ammonium-N in the applied manure corresponded to that obtained from N in commercial fertilizer. There were only very small yield benefits from the use of catch crops. However, this may change over time as fertility builds up in the system with catch crops.

Sulphate leaching and sulphur balances of an organic cereal crop rotation on three Danish soils

Sulphate leaching may reduce the long-term possibility of maintaining the sulphur (S) supply of crops in low input farming systems. Sulphate leaching and S balances were investigated in an organic cereal crop rotation with barley (Hordeum vulgare), grass-clover (Lolium perenne/Trifolium repens and pratense), winter wheat (Triticum aestivum) and barley/pea (Pisum sativum) in mixture at three sites during the first 3 years after conversion to organic farming. Sulphate leaching decreased significantly during the 3 years, and the concentration of drainage water was lowered 1.85.5 times in the third year. Similarly, the S-content of the crops decreased significantly over the years, reflecting lower soil S availability. Sulphur application to spring barley at all sites in Year 2 and at one site in Year 3 increased straw yield by 23% (P<0.01) and grain yield by 13% (NS) on average. Significant fertiliser-S response was restricted to the two sandy soils. Sulphate leaching was quantitatively the most important item affecting the S balance, since excess S was lost by leaching. The S-balance indicated that no substantial S-deficit may be expected in the longer term provided excess S is maintained in the system and the availability is synchronised with plant needs. Otherwise it will in the longer term be necessary on sandy soils to apply S in a plant-available form to avoid the negative effects of S deficiency on yield and quality of crops.

Management Effects on Quality of Organically Grown Winter Wheat

The potential for improving wheat grain quality by management strategies involving crop rotation, catch crops, and organic manure was tested in organic long-term experiments in Denmark and Austria. Growing grass clover in a four-year rotation resulted in a higher wheat yield increase that could not be achieved by including leguminous catch crops in the rotation. Yield was also higher with a pre-crop of pea than of lucerne. The average protein concentration was 132 g kg−1 for grains from the Austrian experiments while the Danish grains held 85 g kg−1. Protein was generally much less affected by the experimental conditions than grain yield. None of the tested management parameters affected grain protein concentrations in the Danish experiment. In the Austrian trial, a significant pre-crop × treatment interaction reflected a positive effect of the animal manure treatment on protein and dry gluten in wheat following pre-crop pea. Danish grains generally contained more soluble polymers of less interest for the baking process than the Austrian ones. The study emphasizes the challenges in improving the quality of organically grown wheat beyond what is predetermined by environmental growth conditions and cultivar. However, baking quality appeared better than could be expected from the quality parameters determined.

Performance of spring barley varieties and variety mixtures as affected by manure application and their order in an organic crop rotation

Abstract In order to obtain a high and stable yield of organic spring barley, production should be optimized according to the specific environment. To test the performance of spring barley varieties under varying cropping conditions, a field experiment was carried out in 2003 and 2004 in a six-field mixed organic crop rotation. We investigated the choice of variety, the order in a rotation, and the application of manure (slurry and farmyard manure; 0 to 120 total-N ha−1) on grain yields of six selected varieties with different characteristics grown in either pure stands or in two spring barley mixtures, each consisting of three varieties. Average grain yield of the barley varieties varied between 3.3 t DM ha−1 and 4.1 t DM ha−1. Grain yields of the two mixtures were 4.0 and 3.6 t DM ha−1, respectively. The varieties/mixtures interacted with crop order and year. Foliar diseases were more severe in the barley following grass-clover with large annual differences in the individual diseases. Despite different rooting depths and nutrient uptake patterns, there was no interaction between variety/mixture and the manure input regarding grain yield. In the 1st year after grass-clover, one of the two mixtures gave higher grain yield than the average yield of the individual varieties in the mixture. This was not the case in the 4th year after grass-clover and for the second variety mixture. Thus, although the present results did not indicate that some barley varieties were better adapted to conditions with low manure input than others, variety mixtures that give a robust and stable organic production may potentially be developed.