A large body of published research now exists on economic, social, technical and policy related aspects of organic production. The dramatic increase in published research over the last 20 years reflects not only the existence of policy support for organic farming in some countries but also the availability of government funding for research on organic farming. This has resulted in a broadening out of organic research from privately funded, specifically organic research organizations, into universities and mainstream research institutes. In parallel, publication of research results from organic farming has increasingly appeared in refereed literature in addition to literature sources more available to farmers and advisors. Research scientists from Europe, North America and Australasia have all made important contributions to the peer-reviewed literature. The literature is dominated by comparisons of organic and other forms of agriculture, although in many cases these comparisons are not fully valid. Research directed specifically at organic systems is often much more valuable in developing improved production systems than comparative research. Research on organic farming embodies both holistic and reductionist research approaches. Trans-disciplinary research also has an important role to play in understanding the complexities of the ecological approach to agriculture typified by organic farming. Working within the principles and standards of organic agriculture will mean that some research will always be specific to organic production systems. However, in future an increased transfer of knowledge from organic to conventional agriculture and vice versa is envisaged.

Nine spring wheat cultivars, selected on the basis of height, tillering capacity and maturity, were grown in differing levels of natural weed presence at three locations in Edmonton and New Norway, Alberta between 2003 and 2004. The objectives of the study were to (1) identify competitive traits in wheat cultivars, (2) determine whether traits associated with competitive ability differ under increasing weed pressure and (3) assess cultivar stability in and adaptation to environments differing in yield potential and weed competition. Eight experimental environments (including conventionally and organically managed fields with and without common oats sown as a weed analogue) were grouped into low, medium and high weed pressure levels, based on mean total weed biomass. Tallness and early heading and maturity were related to increased grain yield at the highest weed level. Greater spikes/m2, tallness and early heading were associated with reduced weed biomass, depending on weed level. Principal component analysis (PCA) revealed that height accounted for a small amount of variation in low weed environments, yet was more important as weed pressure increased. Finlay–Wilkinson (Finlay & Wilkinson 1963) stability analysis demonstrated that cultivars responded differently in environments differing in yield potential and in weed pressure. Older wheat cultivars were generally more yield-stable across environments, while modern semidwarf cultivars were more sensitive to changes in weed level. The cultivar Park (released in 1963) was the most yield- and weed-stable cultivar, coupled with relatively high yields and average weed biomass accumulation, and may therefore be well adapted to low yielding or high weed environments.

Increased harvest index (HI) has been one of the principal factors contributing to genetic yield improvements in spring barley (Hordeum vulgare L.), oat (Avena sativa L.) and wheat (Triticum aestivum L.) cultivars. Although high HI demonstrates high-yielding ability when cultivars are compared, it can also indicate challenges to yield formation when comparisons are made across differing growing conditions. The present study was designed to investigate variation in HI among modern cereal cultivars relative to that brought about by a northern environment, to assess whether HI still explains the majority of the differences in grain yield when only modern cereal cultivars are compared, and to monitor key traits contributing to HI. Stability of HI was also investigated with reference to the role of tillers. Twelve experiments (3 years, two locations, two nitrogen fertilizer regimes) were carried out in southern Finland to evaluate 12 two-row spring barley, 10 six-row barley, 10 oat and 11 wheat cultivars. In addition to HI, days to heading and maturity, length of grain filling period, grain yield, test weight and 13 traits characterizing plant stand structure were measured and analysed with principal component analysis (PCA) to detect traits associated with HI and those contributing to stability of HI. Although only modern cereals were studied, differences among cultivars were significant both in mean HI and stability of HI, and HI was associated with short plant stature in all modern cereal species. Also, single grain weight was associated with HI in all species. Differences between, but not within, species in HI were partly attributable to differences in tiller performance. Grain yield was associated closely with HI except in two-row barley. It may be possible to further increase HI of wheat, as it still was relatively low. High HI did, however, not indicate the degree of success in yield determination when environments are compared.

The present investigation was designed to assess the range of growth-promoting activities of various rhizosphere bacteria on wheat and oat growing in Lanzhou, China. Detection of the N-fixing bacteria by the acetylene reduction assay-based most probable number (ARA-based MPN) method indicated the presence of significant numbers of N-fixing rhizobacteria, i.e. 5·8×106 bacteria/g dry weight of root in association with Chinese wheat variety V4. A total of 24 rhizobacteria was isolated from wheat and oat grown in Lanzhou, China. These bacterial isolates were studied for growth characteristics, nitrogen fixation, phosphate solubilization and indole acetic acid (IAA) production. All the isolates were motile and gram negative. Acetylene reduction activity was detected in all isolates ranging from 124·6 to 651·6 nmol C2H2 reduced/h/vial while almost all isolates produced IAA ranging from 0·2 to 5·1 μg/ml. Only two isolates, ChW1 and ChW6, formed clear zones on Pikovskaia's medium, showing the ability to solubilize phosphates. ChW1 and ChW6 were used to develop fluorescent antibodies to check the cross reactivity of the isolates. Inoculation of these bacterial isolates resulted in higher plant biomass, root area and total N content on Chinese wheat variety Ningchun 2 and Pakistani oat variety Swan under controlled conditions. Among the wheat isolates, ChW5 was the best in promoting wheat growth by increasing its root length, root area, shoot dry weight and total N content. Among oat isolates, ChO3, ChO5 and ChO6 showed significant effects on different growth parameters of their host plants. Using the 15N isotope dilution method, the highest N fixation contribution (0·73 of total plant N) was observed in the wheat plants inoculated with isolate ChW5. Random amplified polymorphic DNA (RAPD) analysis of seven selected isolates showed that the variation within the isolates from different host crops grown in the same soil was quite large and helpful not only in defining the bacterial strains associated with different host crops but also in defining the distances of isolates from standard strains of rhizobacteria used. In conclusion, the present results indicate that the selected bacterial isolates did promote the growth of wheat and oat in ways that could be harnessed to practical benefit for the farmer and consistent with sustainable agricultural practices in China.

The increase of ultraviolet (UV-B) radiation could be a challenge for wheat production systems in Southern Chile, as in other areas. Previous reports have shown that increased UV-B radiation decreases wheat yield by affecting both grain number and grain weight. However, contrasting results have also been published showing no effect on wheat biomass and grain yield. In addition, little is known about the effect of higher UV-B radiation at particular periods of the crop cycle on grain quality traits. The objective of the present study was to evaluate grain yield, yield components and grain quality in response to increased UV-B radiation during key periods of yield component determination. Two experiments were carried out under field conditions in the Universidad Austral de Chile (latitude 39°62′S). Two spring wheat cultivars were exposed to two periods of supplemented UV-B radiation (280–320 nm): (i) between booting and anthesis, c. 20 days, and (ii) from 10 days after anthesis until physiological maturity, c. 40 days. Ultraviolet radiation was increased to levels of 3·8 and 4·9 kJ/m2/day in experimental years 1 and 2, respectively, by using UV-B lamps. At harvest, plants were sampled to quantify aboveground biomass, grain yield, grain number and average grain weight. In addition, protein and gluten concentration of grains were measured. Grain yield was not affected (P>0·05) by the UV-B increase at pre- or at post-anthesis treatments. Similar results were found for each yield component. In addition, grain protein and gluten concentration showed similar values in the increased UV-B and control treatments. Therefore, if increases in UV-B radiation take place during the latter stages of the crop cycle as is expected, the present results do not support the speculation that increases of UV-B radiation in Southern Chile will compromise wheat production systems.

Remotely sensed estimates of biochemical parameters of agricultural crops are central to the precision management of agricultural crops (precision farming). Past research using in situ and airborne spectral reflectance measurements of various vegetation species has proved the usefulness of hyperspectral data for the estimation of various biochemical parameters of vegetation. In order to exploit the vast spectral and radiometric resources offered by space-borne hyperspectral remote sensing for the improved estimation of plant biochemical parameters, the relationships observed between spectral reflectance and various biochemical parameters at in situ and airborne levels needed to be evaluated in order to establish the existence of a reliable and stable relationship between spectral reflectance and plant biochemical parameters at the pixel scale. The potential of the EO-1 Hyperion hyperspectral sensor was investigated for the estimation of total chlorophyll and nitrogen concentrations of cotton crops in India by developing regression models between hyperspectral reflectance and laboratory measurements of leaf total chlorophyll and nitrogen concentrations. A comprehensive and rigorous analysis was carried out to identify the spectral bands and spectral indices for accurate retrieval of leaf total chlorophyll and nitrogen concentrations of cotton crop. The performance of these critical spectral reflectance indices was validated using independent samples. A new vegetation index, named the plant biochemical index (PBI), is proposed for improved estimation of the plant biochemicals from space-borne hyperspectral data; it is simply the ratio of reflectance at 810 and 560 nm. Further, the applicability of PBI to a different crop and at a different geographical location was also assessed. The present results suggest the use of space-borne hyperspectral data for accurate retrieval of leaf total chlorophyll and nitrogen concentrations and the proposed PBI has the potential to retrieve leaf total chlorophyll and nitrogen concentrations of various crops and at different geographical locations.

In northwest (NW) Europe, oilseed rape (OSR) is often used as a preceding crop for winter wheat. Due to its low N harvest index (HI) and to favourable soil conditions after harvest, large amounts of mineral N remain in the soil, which cannot completely be taken up by the subsequent wheat crop. This increases the risk of N leaching into the groundwater during the following winter. Recently, semi-dwarf genotypes of OSR were developed and made commercially available that show similar yields but reduced height growth compared to conventional genotypes. The present authors hypothesized that the introduction of dwarfing genes leads to an increase in HI for dry matter (DM) and for N of OSR. As a consequence, semi-dwarf genotypes would accumulate less aerial biomass, return fewer plant residues to the soil and need less N to achieve yield maximum compared to conventional hybrids or open pollinating varieties. This may lead to a reduced risk of N leaching after growing OSR. In order to test this hypothesis, field trials conducted in 2003/04–2005/06 near Kiel in NW Germany combined four commercial varieties of OSR (Express, Talent, Trabant and Belcanto as semi-dwarf genotype), two seeding dates (mid-August and beginning of September) and eight mineral N fertilization rates (0–240 kg N/ha). On average in 2003/04–2004/05, the semi-dwarf genotype Belcanto achieved significantly less seed yield (4·44 t/ha) than the other varieties (4·65–4·88 t/ha). However, all varieties tested required similar N fertilization to achieve maximum yield. In addition, N offtake by the seeds did not differ. No interaction between genotype and N treatment was observed. Detailed analysis of DM accumulation and N uptake during the growth period revealed only small differences between the varieties in the averages of all N treatments and both years. At harvest, Belcanto produced more pods/m2 and a slightly higher 1000 seed weight. Nevertheless, HI and N HI were similar for all genotypes. It is concluded that, despite its lower plant height, the semi-dwarf genotype did not provide the opportunity to reduce the risk of N leaching after growing OSR.

The objective of the present paper was to propose a statistical approach to support selection of the most promising genotypes in a breeding programme. The approach is based on applying two state-of-the-art statistical methodologies, likelihood-based path analysis and model-based cluster analysis. The first method is applied to find a causal mechanism lying behind a biological process of development of final crop yield. These results are then used for weighting traits to be used in cluster analysis, which helps select genotypes possessing a desirable level of yield and yield-contributing traits. An application of the approach is presented for a 2-year study on 22 grasspea genotypes, two cultivars (Derek and Krab) and 20 mutants from those cultivars. Seed yield/plant and seven yield-related traits were studied. Among these, plant height, number of branches/plant, pod length and number of seeds/plant determined seed yield; number of pods/plant influenced seed yield only for 2002. These results were used for appropriate weighting in cluster analysis, which indicated that cultivar Krab and its two mutants, K3 and K64, had the best level of the traits and were the most stable genotypes.

Young leaves and pods of okra (Abelmoschus esculentus (L.) Moench) are edible, and so a crop management strategy for removing edible leaves while sustaining good pod yields is required. Pruning treatments were imposed on apically debudded okra plants for 3 years to assess effects of removing a quarter, half or three-quarters of the primary branches on growth and fresh leaf and pod yields. Pruning significantly (P<0·05) delayed fruiting by 8–10 days, extended length of harvest duration by 12–15 days and increased number of pods/plant by 10–40% and pod yield by 9–36% more than the control plants which had neither apical bud removal nor pruning. However, no difference in pod weight or pod length was found between these treatments and the control. Three-quarters pruning significantly (P<0·05) increased fresh leaf yield by 29–49%, but not all the leaves were desirable for consumption because of high fibre content. Decreases were seen in the numbers of secondary branches, shoot dry weight and pod yields (by 40–57, 22–36 and 22–30%, respectively, more than a quarter or half pruning). Although early production of pods in the control plants is often important for early maturity and high market prices, the present study found that a delay in fruiting, an extension in length of harvest duration and an increase in pod yield in plants with a quarter or half pruning enhanced staggered production and maximal pod yield. This helps to ensure a better market price and to enable growers avoid a glut on the market. A direct promotional effect of pruning on pod yields provides a possible strategy for growing okra for both leaf and pod harvests. A quarter or half pruning from the upper parts of the main stems of apically debudded plants to ensure good production and quality of leaves and pods is therefore recommended if okra is to be grown for both leaf and pod yields.

L-methionine is a sulphur-containing nutritionally essential amino acid. It has a number of important roles in epidermal and dermal tissues of the integument of animals. Failure of normal function of these tissues in the hoof (claw) is a cause of lameness in cattle. Little is known about quantitative relationships between post-absorptive concentrations of nutrients including sulphur-containing amino acids and uptake and utilization by epidermis and dermis of the bovine claw. These parameters were studied at the tissue level by use of an established in vitro claw explant system using tissue from cattle of beef or dairy origin and L-[35S]-labelled methionine as tracer. The results showed that uptake of L-methionine by freshly prepared solear explants in Dulbecco's Modified Eagle Medium/F-12 Nutrient Mix (DMEM/F12) (1:1) medium containing 1·0 mmol L-methionine/litre was concentrative after 5–8 min, essentially linear for up to 10 min and became curvilinear thereafter. Maximum uptake and steady state conditions were obtained at approximately 30 min. Further measurements were made following 21 h incubation in culture medium. Under conditions of varying concentrations of L-methionine and measurement of uptake after 30 min, the presence of a saturable curve, that obeyed Michaelis–Menten kinetics, was demonstrated. Values of 3·61 mmol/litre and 5·84 mmol/kg intracellular water/30 min were obtained for KM and Vmax, respectively. Uptake was not influenced by L-cysteine and L-cystine concentrations in the culture media.

Similar culture and incubation conditions were used in subsequent studies of DNA and protein synthesis. These showed that rates of incorporation of L-methionine into protein fractions and stimulation of DNA synthesis measured by methyl-thymidine incorporation were dependent on L-methionine concentrations in the medium. Maximal rates occurred at approximately 50 μmol/litre, which is in the normal physiological range, and at 1% of maximum uptake capacity. Examination of histological sections by autoradiography showed localization of L-[35S]-labelled methionine in basal and suprabasal epidermal cells with limited retention in dermis. Measurement, by a range of histological, immunohistochemical, electrophoretic, western blotting and autoradiographic techniques, provided further evidence of L-methionine-dependent regulation of proliferation, differentiation and synthesis of proteins under physiological concentrations, by epidermal horn-forming cells.

A key role for L-methionine is suggested in the production of horn in bovine claw. The extrapolation of these in vitro data provides guidance for strategies to optimize methionine supply to claw tissues in vivo. Such extrapolation suggests the appropriateness of delivery of systemic concentrations of 50 μmol L-methionine/litre to maximize proliferative and protein depositional activity in solear epidermis and dermis in vivo.