Deliverables
Effects of intercropping on cereal quality are not always expressed in effects on economic worth due to the use of threshold levels when marketing grain, and also the need for achievement of multiple targets for certain end-uses. The effects of intercropping on the quality of wheat for breadmaking are generally positive but estimates of improved worth of 2 to 5%, when the maximum premium for breadmaking wheat is 22.5% over the feed wheat price, need to be balanced against cost penalties for admixture and/or effective separation of the cereal from the pulse.
The effects of intercropping with pea on the quality of barley for malting are likely to be negative, either due to the costs of admixture and/or cleaning (not quantified) or due to increases in grain nitrogen concentration (reducing worth/t by 1-2% when the maximum premium for malting barley is 26.5% over the feed barley price). Not all the effects of intercropping on grain quality are assessed at the point of sale of grain. These effects may be more relevant to organic farmers using grain on farm, or to organic farmers with a financial interest in the processing chain.
Intercrops have a stronger ability than sole crops for disease control on barley at relatively high levels of infestation. Effects on pea diseases were small. Pest damage due to Sitona lineatus and Bruchus pisorum may increase with intercropping. On the contrary, no difference was found regarding Acyrthosiphon pisum and Cydia nigricana
Intercropping wheat with faba bean, wheat with pea regularly increased the nitrogen concentration of the cereal grain, and less regularly, the nitrogen concentration of the grain legume. Sulphur concentration of the cereal was also increased by intercropping, but to a lesser extent compared with effects on nitrogen concentration. For example, nitrogen concentration (g/kg) in wheat additively intercropped with faba bean was increased by a weighted average of 8% across all sites, but sulphur concentration was only increased by 4%. Intercropping wheat with grain legumes increased SDS-sedimentation volume, Hagberg falling number and loaf quality of the wheat.
Economic profitability of pea-barley intercropping was strictly related to pea and barley yield performance and to production cost considered in each European environment. The net income of the intercrop was always higher than one of two sole crop. This is an important observation since farmers only choose to intercrop if they require both crops.
Intercropping barley with pea increased the nutritive value of the barley through increasing protein concentration and slightly improving in vitro digestibility. Intercropping cereals with grain legumes usually had no, or slightly positive effects, on mean grain weight and grain specific weight (kg/hl), although negative effects were seen in Italy. Intercropping barley with pea had only minor or inconsistent effects on the quality of a following wheat crop.
The development of the STICS simulation model intercrop module model through the extrapolation of the sole crop model and the parameterisation from experimental data recorded in sole crops allows an accurate simulation of the interactions for resources between intercropped species. The simulated responses of the intercrops are in agreement with the observations from the experimental datasets. The STICS model seems to be an operational tool for simulating growth and N accumulation in pea-barley intercrops and for predicting the composition of the final mixture according to soil N supply.
However the experiments used for the parameterization in sole crops and the validation in intercrops were not independent and were carried out with only one limiting factor (nitrogen). This model needs to be tested under a wider range of situations and in the case of other limiting factors occurring in low-input farming systems. The model is useful for testing technical strategies. Strategies to get the best agricultural results can be different according to locations and output objectives: favouring pea or barley, grain or forage utilization.
Nitrogen sources is used 20-30% more efficiently by pea-barley intercrops compared to the respective sole crops showing a high degree of complementarity between pea and barley across very different growing conditions in Europe. As a rule 20 to 40% more efficient soil mineral N uptake was achieved by the intercrops as compared to the sole crops. Similarly the use of phosphorous, potassium and sulphur was used much more efficiently in intercrops. A relative greater crop soil N uptake in barley was found forcing pea to rely on N2 fixation when intercropped raising the percent of total N derived from N2-fixation. However, increasing the quantitative N2 fixation inputs require management practices that increase N demand by pea. Intercropping and systematic planting designs is one of several management tools to adapt when optimizing local plant N accumulation.
A survey among 63 organic farmers in European countries (D, DK, F, I and UK) gave essential evidence on existing experience among organic farmers on intercropping. Intercropping is a valid system for stabilizing the performance of arable crops grown in organic farming in quantity and quality. Easier harvest and less lodging, high competitive ability towards weeds, less demand for fertilization and more stable yield was most frequently quoted benefits. Extra costs for separation if seeds if they are to be sold on the market and difficulties in weed harrowing were quoted as the most important barriers. Suitable species and cultivars for intercropping have to be selected. Technical problems like harvest losses and difficult seed purification can be solved. Farmers should be encouraged and supported to choose growing systems of higher complexity, biodiversity, and stability. The knowledge can be used by farmers, advicers and scientist to develop further intercropping within EU agriculture.
Independent of crop yield performance between sites and the varying conditions of weeds in terms of species and biomass, intercrops and barley sole crops reduced weed pressure better than pea sole crops in all cases, with no difference intercrop designs. A better efficiency of barley and the intercrops for DM accumulation and soil N uptake was the explanation for the greater competitive ability against weeds of these crops compared with pea sole crops. Intercropping pea with barley appears to be a very efficient management method for reducing weed infestation in organic farming, whereby mechanical weeding and burning of weeds can be avoided.
Intercropping of pea and barley was demonstrated in three organic farms in Northern Germany and two organic farms in southern Italy. Demonstration trials were used in dissemination of the intercropping methodology to visiting farmer groups. Demonstration trials confirmed some of the main conclusion from the scientific experiments, eg. intercropping advantage and improvement of cereal protein quality.
The agronomic performances of evaluated intercropping series in different European agricultural context showed that the pea-barley intercrop is as a profitable technique in organic farming. Both additive and replacement series demonstrated yield advantage in the different climatic conditions. Confirming the suitability of spring pea-barley intercropping in North and Central Europe, the results demonstrated that yield advantage is further reached in the Mediterranean environment (Southern Italy) by growing pea-barley intercrop in spring season, that is a no-typical growing season for cereal and legume in rainfed condition. Analysis of relative variability (stability) of Land Equivalent Ratio indicated that pea-barley intercrop maintain the advantage also when pea competition is high (additive series).
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