Perennial clovers and ryegrasses as understorey crops in cereals

Perennial crops undersown in cereals provide ground cover from harvest of the cereal crop to sowing of the next crop. Such cover crops can e.g. reduce soil erosion, nutrient leaching and N fertiliser requirements of the succeeding crop. The objective of this thesis was to develop guidelines on how to prevent grain yield losses due to competition from the perennial crops or to increase the yield of the main crops. The effects of species and time of undersowing of perennial crops in spring cereals, and the management of an intercropping system in which winter oilseed rape or consecutive crops of winter wheat were established in a remaining crop of white clover, were studied. The biomass of undersown cover crops by the time of the harvest of spring barley was significantly reduced with each delay in the undersowing, but the increase in biomass during autumn was generally not affected. Italian ryegrass (Lolium multiflorum Lam) and perennial ryegrass (Lolium perenne L.) reduced the grain yield by 6 and 1%, respectively, but may both be suitable as cover crops with the appropriate main crop, time of undersowing and seed rate. Undersown white clover (Trifolium repens L.)/perennial ryegrass mixtures kept soil mineral N as low as pure ryegrass and improved the residual effect. This suggests that clover in the cover crops may reduce the N fertiliser requirements of the succeeding crop without increased N leaching. Grain yields were smaller in the wheat/clover system than with wheat alone when the wheat was direct drilled and larger when sown after stubble cultivation. Direct drilled wheat and rape yielded more with clover varieties less adapted to the cold climate than with varieties in common use in the area. Grain yield increased, weeds were efficiently controlled and the white clover crop maintained by applying herbicides that mainly act as germination inhibitors when a third consecutive wheat crop had 1–2 leaves. It was possible to conclude that (1) the tillage performed in conjunction with the sowing of wheat, (2) the weed control practice, and (3) the choice of clover variety, have large effects on the yield of the winter annuals in the intercropping system

Vem är OSCAR? – understödjande grödor i odlingssystemet

Ensidiga växtföljder med ettåriga grödor risker att långsiktigt minska bördigheten. Ett sätt att motverka detta är att praktisera ett jordbruk där marken bearbetas försiktigt och där understödjande grödor används för att skydda markytan och öka bördigheten. FP-7 projektet OSCAR syftar till att utveckla funktionella odlingssystem där marken är täckt av växter under en stor del av året, där den biologiska mångfalden är hög och och där behovet av och mängden jordbearbetning är litet. Föredraget presenterar översiktligt OSCAR-projektet

Biomass production and phosphorus retention by catch crops on clayey soils in southern and central Sweden

Catch crops are a potential option to reduce phosphorus (P) losses, but little is known about their establishment success and capacity to retain P on clayey soils in regions with short autumns, e.g. Sweden. This study screened biomass production and P retention by eight catch crop species: the perennials chicory (Cichorium intybus L), cocksfoot (Dactylis glomerata L), perennial ryegrass (Lolium perenne L.) and red clover (Trifolium pratense L) and the annuals phacelia (Phacelia tanacetifolia L), white mustard (Sinapis alba L), oilseed radish (Raphanus sativus L oleiformis) and white radish (R. longipinnatus). The catch crops were grown at six field sites, where the perennial species were under-sown with barley and the annual species were after-sown following barley harvest. Biomass production, P content in above-ground and below-ground plant parts and content of available P in the soil were determined in autumn and survival rate of the catch crops in the following spring. Biomass production and P retention in autumn both differed significantly between species (p < 0.0001), and were greatly affected by site-specific conditions and time of sowing, which differed between experiments. Growth of catch crops can also be suppressed by low precipitation. Content of P in roots varied substantially between species, a factor which must be considered in species comparisons. The under-sown species produced more or equivalent amounts of biomass, retained more or equivalent amounts of P in autumn and survived better over winter than the after-sown species. Thus under-sown catch crops generally seem more suitable as catch crops for P

Assessing the effect of intercropped leguminous service crops on main crops and soil processes using APSIM NG

CONTEXT: To improve agricultural sustainability, alternative cultivation methods and assessment tools need to be developed. Integrating service crops (SC) can potentially increase cropping system multifunctionality and mitigate negative climate and environmental impacts of agriculture. OBJECTIVES: (1) Calibrate oats, winter wheat and red clover SC, grown as sole crops and intercrops, in the cropping system model APSIM NG for northern Europe climate conditions. (2) Use the calibrated crop modules to assess ecosystem processes from an intercropping system. (3) Discuss the role of mechanistic crop models in assessing ecosystem services and disservices from complex cropping systems. METHODS: The crops were calibrated with data from an oats-winter wheat cropping sequence at two field sites. Thirty weather datasets were created from historical weather data to generate weather-dependent variability in crop performance and related processes. The assessment compared two scenarios, with or without an intercropped red clover SC sown in oats and terminated the following spring in winter wheat. Outputs representing processes related to important ecosystem services were extracted from the simulations. RESULTS , CONCLUSIONS: Calibration of the three crops resulted in satisfactory biomass levels at the end of the growing season. Including a SC reduced oat yield, but increased winter wheat yield in two-thirds of simu- lations. Model outputs showed that including a SC resulted in 33-79% more fresh soil organic carbon, depending on site, compared with no SC. Nitrogen (N) uptake by both crops was highest in the SC scenario. In oats, N losses did not differ between the two scenarios, while in winter wheat the SC scenario had approximately 50% lower N leaching losses , 30% higher gaseous N emissions. However, in the fallow period from winter wheat harvest through to spring, both types of N losses were elevated in the SC scenario. The SC scenario had only a minor effect on water dynamics, causing a small reduction in soil water content. SIGNIFICANCE: In this paper we give an example of how APSIM NG can be used to assess ecosystem services from complex agricultural systems using a case study with intercropping of cereals and leguminous SCs. APSIM NG was useful in providing a holistic assessment , we show that intercropping with a SC can improve cropping system performance and reduce negative impacts, but long-term strategic management of N is required to prevent increased losses. To further improve simulation of intercrops more accurate simulation of early growth is needed for all crops included

Cut fallow to replace black fallow in an organic production system

Couch grass (Elymus repens) has large impact on yield and management strategies in temperate areas of the world. The control is to a large extent based on repeated soil cultivations in organic farming. Our aim was to investigate methods to improve the competitive effect of white clover by management. The hypothesis was that cutting (fragmentation) of the rhizomes by making slits in the soil by a spade (spading) would increase the number of couch grass shoots, thus improve the effect of repeated mowing. We conclude that Cross cutting to 10 cm could reduce the amount of rhizomes, but that the effect is variable. We also conclude that the cross cutting do not improve the effect of mowing. Cross cutting reduce the amounts of couch grass shoots

Potential phosphorus release from catch crop shoots and roots after freezing-thawing

Background and Aims Catch crops used for mitigating nutrient losses to water can release phosphorus (P) when exposed to repeated freezing-thawing cycles (FTCs). This study sought to evaluate potential P losses from shoots and roots of eight catch crops. Methods Shoots and roots sampled from perennial ryegrass (Lolium perenne L.), cocksfoot (Dactylis glomerata L.), chicory (Cichorium intybus L.), phacelia (Phacelia tanacetifolia L.), red clover (Trifolium pratense L.), white mustard (Sinapis alba L.), oilseed radish (Raphanus sativus var. oleiformis L.) and white radish (R. sativus var. longipinnatus L.) were treated with no freezing, one single FTC, four continuous FTCs and four discontinuous FTCs. All samples were analysed for water-extractable P (WEP), and root samples also for characteristics such as specific root surface area (SSA). Results Freezing-thawing significantly increased potential P losses from both shoots and roots compared with no freezing. The two radish species and white mustard contained significantly higher concentrations of WEP than the other species, among which chicory and phacelia had the lowest WEP. On average, shoots had 43% higher WEP than roots. Cumulative P release from shoots and roots was strongly correlated with their total-P content (p=0.006 and p=0.002, respectively). Cumulative release of P from taproots was correlated with SSA (p=0.03). Conclusions Chicory, and possibly phacelia, appear to be promising catch crops for P

Effect of short-term perennial leys on life cycle environmental performance of cropping systems: An assessment based on data from a long-term field experiment

Modern agriculture's dependence on the intensive use of inputs, such as chemical fertiliser and pesticides, leads to high environmental impacts and, possibly, vulnerability in food security, since most of these inputs are im-ported from other countries. This calls for more sustainable and resilient agricultural practices. Diversification of crop rotations, e.g. by including perennial leys, enhances provision of ecosystem services, leading to healthier crops and increased yields. Perennial crops also increase soil organic carbon (SOC) stocks, which is interesting from a global warming mitigation perspective. In addition, legume-rich leys can utilise atmospheric nitrogen (N) through symbiotic association with N2-fixing bacteria. However, few studies have evaluated the effects of short-term perennial leys in rotation on cropping system performance over long periods and under different conditions. In this study, we used data from three sites in a long-term experiment in Sweden (initiated in the 1960 s), in combination with Life Cycle Assessment methodology, to assess the environmental and yield effect of including ley in crop rotations. Two N fertiliser regimes (High, Low) in combination with three six-year crop rotations, consisting of either i) two-year mixed grass-legume ley, ii) two-year pure grass ley or iii) annual crops without ley, were compared. Environmental impacts (climate impact, energy resource depletion, eutrophication poten-tial) of the different combinations were quantified per kg harvested crop (expressed in cereal units, CU) and per hectare. The lowest environmental impact, at all sites, was found for the crop rotation with two-year mixed ley under the Low N regime. On average, this combination resulted in 329 g lower GHG emissions per kg CU than the crop rotation without ley and Low N, primarily due to lower input of chemical N fertiliser, which reduced the impact from fertiliser production and soil N2O emissions. Comparison of mean SOC change over the study period revealed reduced SOC stocks for all rotations and all sites, especially in the rotation without ley. Therefore, including short-term perennial leys, especially leys containing legume species, in crop rotations can be a useful tool in meeting policy targets on reducing the environmental impacts of agriculture, and in reducing the dependence on purchased agricultural commodities. However, despite the potential benefits of rotational leys, the market demand for the produced ley biomass may be insufficient. Hence, incentives to increase demand are necessary to promote large-scale adoption, for example, for use in bioenergy production and feed