Multi-model uncertainty analysis in predicting grain N for crop rotations in Europe

Realistic estimation of grain nitrogen (N; N in grain yield) is crucial for assessing N management in crop rotations, but there is little information on the performance of commonly used crop models for simulating grain N. Therefore, the objectives of the study were to (1) test if continuous simulation (multi-year) performs better than single year simulation, (2) assess if calibration improves model performance at different calibration levels, and (3) investigate if a multi-model ensemble can substantially reduce uncertainty in reproducing grain N. For this purpose, 12 models were applied simulating different treatments (catch crops, CO₂ concentrations, irrigation, N application, residues and tillage) in four multi-year rotation experiments in Europe to assess modelling accuracy. Seven grain and seed crops in four rotation systems in Europe were included in the study, namely winter wheat, winter barley, spring barley, spring oat, winter rye, pea and winter oilseed rape. Our results indicate that the higher level of calibration significantly increased the quality of the simulation for grain N. In addition, models performed better in predicting grain N of winter wheat, winter barley and spring barley compared to spring oat, winter rye, pea and winter oilseed rape. For each crop, the use of the ensemble mean significantly reduced the mean absolute percentage error (MAPE) between simulations and observations to less than 15%, thus a multi–model ensemble can more precisely predict grain N than a random single model. Models correctly simulated the effects of enhanced N input on grain N of winter wheat and winter barley, whereas effects of tillage and irrigation were less well estimated. However, the use of continuous simulation did not improve the simulations as compared to single year simulation based on the multi-year performance, which suggests needs for further model improvements of crop rotation effects.     

The Influence of Crop Rotation with an Increasing Content of Cereals on Photosynthetic Potential of Winter Wheat

In years 1982–1985 flag leaf area, concentration of chlorophyll and macronutrients (N, P, K, Ca, Mg, Na) and also their correlations to grain yield in static field experiment were studied. The main experimental plots comprised crop rotations containing 50, 75, 100% cereals. Treatments with or without irrigation were subplots and nitrogen levels (0, 60, 120, 180 kg N/ha) were sub-sub-plots.
The cultivation of winter wheat in rotations containing more than 50% cereals affected the drop of winter wheat grain yield, which was especially high on the plots without nitrogen fertilization or with low N level. The dose of 120 kg N/ha gave the highest grain yield in each rotation and, at the same time, decreased to minimum the differences between them, although wheat grown in the full cereal rotation yielded much less. The response of wheat grain yield to previous crop was affected by photosynthetic potential of a plant, which was constituated by flag leaf area and concentration of chlorophyll. The deteriorating nutrient economy in wheat plants grown in rotations containing more than 50% cereals decreased the photosynthetic potential of wheat. In addition, in these rotations the importance of macronutrients concentration in the flag leaf at anthesis as a source of nutrients for the developing grain is visible.     

Effect of Different Preceding Crops and Crop Rotations on Yield of Winter Oil-seed Rape (Brassica napus L.)

To determine the effect of different preceding crops and crop rotations on the grain yield of oil-seed rape, a long-term rotation experiment was conducted at the Hohenschulen experimental station in Kiel, NW Germany. Additional factors included the nitrogen fertilization and the fungicide application. The results reported herein are based upon the harvest years 1988 to 1993. Averaged over the different rotations and husbandry treatments, the grain yields in the 6 experimental years varied between 2.71 t ha^?1 and 3.99 t ha^?1. In contrast, the effect of the different husbandry treatments was smaller and non significant. Averaged over 6 years, only the fungicide application caused small yield increase of 0.2 t ha^?1. The highest grain yields of 3.77 t ha^?1 or 3.65 t ha^?1 occurred when oil-seed rape was directly following peas. Low yields between 3.15 tha^?1 and 3.33 tha^?1 were obtained when oil-seed rape was grown after oilseed rape. The lowest grain yield of 3.13 t ha^?1 was produced with oil-seed rape grown in monoculture only. In rotations with oil-seed rape following a preceding cereal crop (wheat or barley), the grain yields averaged between 3.22 tha^?1 in a two course rotation and up to 3.44 tha^?1 in a four course rotation. In general, the yields of oil-seed rape increase with the length of the rotation and the length of the break between two oilseed rape crops. The yield component number of seeds per m² was affected by the previous cropping accordingly, whereas the thousand seed weight did not respond to the cropping history. Based upon disease assessments in the first years of this experiment, we argue that an increase in the incidence of fungal diseases has considerably contributed to the yield decrease of oil-seed rape in short rotations.     

Crop sequence,crop protection and fertility management effects on weed cover in an organic/conventional farm management trial

A survey of 128 plots, in 2008, of a trial where the effects of crop protection can be separated from those of fertility management, generated weed cover data within six crops (winter wheat, winter barley, spring barley, potatoes, cabbages and a grass/clover ley). The effects of the 2008 crop types, of the two preceding crops and of organic and conventional crop protection and fertility management, were assessed using mixed-effects models and constrained ordination. Cover data for 22 weed species and for monocotyledon, dicotyledon, annual, perennial and total weed cover were used. Cover of 15 weed species, and of the five weed groups, was significantly affected by 2008 crops, with cover highest in spring beans and cabbage. Nine and four weed species 2008 cover were significantly related to crops grown in 2007 and 2006 respectively, as were dicotyledon, annual and total weed cover, but not monocotyledon or perennial cover. Cover of 15 species, and the five groups, was significantly higher in plots with organic crop protection, but only eight species and annuals were significantly affected by fertility management. Crop:crop protection produced the most significant interactions with most cover in organically managed plots. Five species, perennials and total weed cover produced significant three-factor models. The greatest weed cover was in organic crop protected but conventionally fertilised spring barley and the least in totally conventional winter barley. Other factors such as crop density and mechanical weeding also affected 2008 weed cover. The ordination indicated that most of the 22 species were strongly associated with crops from all three years. The sequence of crops in the rotation had a profound effect on weed cover. Where three spring-sown, difficult to weed, crops were grown in sequence (spring beans, potatoes and vegetables, spring barley) weed cover increased. However, cover was limited in grass/clover and some cereal plots with different preceding crops. Models predicting weed cover may need to take into account crop sequences within crop rotations, as well as the more usual management inputs.     

Results of Long-term Experiments with Growing Flue-cured Tobacco (Nicotiana tabacum L.) in Monoculture and Different Types of Crop Rotations

In broadly conceived long-term experiments, tobacco was grown in monoculture and with different crop rotations. This paper presents results in terms of the yields achieved and the major yield components for the crops grown, and the proportion of particular tobacco quality classes obtained. In addition to tobacco monoculture (initially only fertilized and later also unfertilized) as the key crop, different types of crop rotations included, besides tobacco, the following crops: winter wheat, maize, soybean, oil-seed rape, and red clover. Experiments involved two 2-year and two 4-year crop rotations, and a 3-year, a 5-year, and a 6-year crop rotation. Experiments were set up on luvic semigley on multilayered Pleistocene sands. Average 10-year results suggest that there is an advantage of crop rotation over monoculture for tobacco leaf yields. The influence of different crop rotation types on yields of other crops was variable, tending towards higher values as the number of crops in rotation was increased. Values obtained for yield components should be considered from two angles: some of the values were primarily influenced by genetic factors, while others were influenced by ecological factors, including crop rotation as an overall biological buffer. With regard to quality classes (IB-III), the growing of flue-cured tobacco in crop rotation represents a great advancement relative to its growth in monoculture, even in a narrower crop rotation.     

Productivity of organic and conventional arable cropping systems in long-term experiments in Denmark

A field experiment comparing different arable crop rotations was conducted in Denmark during 1997–2008 on three sites varying in climatic conditions and soil types, i.e. coarse sand (Jyndevand), loamy sand (Foulum), and sandy loam (Flakkebjerg). The crop rotations followed organic farm management, and from 2005 also conventional management was included for comparison. Three experimental factors were included in the experiment in a factorial design: 1) crop rotation (organic crop rotations varying in use of whole-year green manure (O1 and O2 with a whole-year green manure, and O4 without), and a conventional system without green manure (C4)), 2) catch crop (with and without), and 3) manure (with and without). The experiment consisted of three consecutive cycles using four-course rotations with all crops present every year, i.e. 1997–2000 (1st cycle), 2001–2004 (2nd cycle), and 2005–2008 (3rd cycle). In the 3rd cycle at all locations C4 was compared with two organic rotations, i.e. O2 and O4. The O2 rotation in the third cycle included spring barley, grass-clover, potato, and winter wheat, whereas C4 and O4 included spring barley, faba bean, potato, and winter wheat. For the O2 rotation with green manure there was a tendency for increased DM yield over time at all sites, whereas little response was seen in N yield. In the O4 rotation DM and N yields tended to increase at Foulum over time, but there was little change at Flakkebjerg. The DM yield gap between organic and conventional systems in the 3rd cycle varied between sites with 34–66% at Jyndevad, 21–44% at Foulum, and 32–52% at Flakkebjerg. The inclusion of grass-clover resulted in lower cumulated yield over the rotation than the treatment without grass-clover. The use of manure reduced the DM yield gap between conventional and organic systems on an average by 15 and 21%-points in systems with and without grass-clover, respectively, and the use of catch crops reduced the yield gap by 3 and 5%-points in the respective systems. Across all crops the agronomic efficiency of N in manure (yield benefit for each kg of mineral N applied) was greater in O4 compared with O2 for all crops.     

Optimizing nitrogen use efficiency in wheat and potatoes: interactions between genotypes and agronomic practices

One approach to decrease the environmental impact of crop production and reduce costs is to optimize agronomic practices and genotypes so that nutrients are used more efficiently. In this study the effects of agronomic practices (rotations, crop protection, fertilization) on yields, nitrogen use efficiency (NUE) and associated parameters were studied in an experiment using two winter wheat genotypes (Cordiale and Scaro) in one season and two potato genotypes (Sarpo Mira and Sante) in two seasons. The wheat showed no varietal differences in yield and NUE; instead the fertilization regime was the main factor affecting yield and NUE with higher values observed when conventional fertilization was used. The exception was for wheat grown after three years grass/clover ley when there was no added yield benefit from conventional fertilization of the organically bred variety (Scaro). This demonstrates the potential for N fixing crops to provide sufficient N to high yielding cereals if grown for long enough prior to planting. The greatest gains in NUE were achieved by combining an N efficient genotype with conventional crop management in an organic rotation. Fertilization and genotypic variation were the main factors affecting potato tuber yield and NUE, with the late maturing Sarpo Mira displaying elevated yields and NUE compared with the early maturing Sante. The use of organic fertility sources resulted in lower NUE, but N release from organic sources may increase NUE of future crops. This highlights the need for long-term nutrient balance and modelling studies to assess NUE at the crop rotation scale.     

The Effect of Different Preceding Crops on the Development, Growth and Yield of Winter Barley

Reliable estimations of the yield response of winter barley to different preceding crops are necessary for the design of crop rotations.
The grain yield and yield components of winter barley (cv. Tapir ) following either rapeseed, oats, wheat or barley were determined in five years of field experiments on a sandy loam (Luvisol) at the Hohenschulen experimental station near Kiel, Germany, F.R. The growth, development and incidence of take-all ( Gaeumannomyces graminis var. tritici ) was measured in a total of three years. On average over the five years barley grown after oats yielded 0.8 t per ha (11 %) more than barley following wheat which was mainly due to a higher number of ears per m². Barley following either oats or rapeseed produced a higher dry weight and a larger number of tillers per m² compared with barley grown after wheat or barley. This effect was already-present at the sampling date before winter. Take-all ratings were constantly higher in barley following a susceptible crop, but only reached a severe level late in the season and therefore could not explain the observed differences in growth, development and subsequently grain yield. Since no other pathogens affected the development other non-pathogenic causes must be considered as main causes for the described observations and yield differences.     

Forage and Food Legumes in a Multi‐Year,Wheat‐Based Rotation Under Drought‐Stressed Conditions in Northern Syria’s Medium Rainfall Zone

Long‐term crop rotation trials were designed to assess sustainability of alternatives to traditional fallow and monocropping. The trial described here (6 years) involved wheat (Triticum aestivum L.) in rotation with lentil (Lens culinaris L.), forage vetch (Vicia sativa), pasture medic (Medicago spp.), fallow and watermelon (Citrullus vulgaris). Barley (Hordeum vulgare L.) was compared with wheat for an additional 2 years. Cereal grain and straw yields were highest with fallow and watermelon followed by vetch, lentil and medic; the latter showed no differential effect of variable grazing intensity. Fertilizer N increased yields except in the low‐rainfall years (less than 250 mm). Barley out‐yielded wheat in terms of grain, but not straw. Medic yielded highest in dry matter, whereas lentil produced highest seed yield. Despite the difficulty of assessing crop and animal‐oriented rotations because of non‐commonality of outputs, economic considerations are foremost, but other benefits of rotations (soil quality, water‐use relations) are also relevant to the overall assessment of cereal‐based Mediterranean rotations. The study suggested barley rather than wheat as the desired cereal in rotation with legumes in this marginal‐rainfall (350 mm) environment and provided support for the viability of vetch and lentil in the cropping system. Given the importance of sheep in the region’s farming system, vetch is likely to have a major role in crop rotations.     

Winter cereal yields as affected by animal manure and green manure in organic arable farming

The effect of nitrogen (N) supply through animal and green manures on grain yield of winter wheat and winter rye was investigated from 1997 to 2004 in an organic farming crop rotation experiment in Denmark on three different soil types varying from coarse sand to sandy loam. Two experimental factors were included in the experiment in a factorial design: (1) catch crop (with and without), and (2) manure (with and without). The four-course crop rotation was spring barley undersown with grass/clover – grass/clover – winter wheat or wheat rye – pulse crop. All cuttings of the grass–clover were left on the soil as mulch. Animal manure was applied as slurry to the cereal crops in the rotation in rates corresponding to 40% of the N demand of the cereal crops.Application of 50 kg NH₄–N ha^?1 in manure increased average wheat grain yield by 0.4–0.9 Mg DM ha^?1, whereas the use of catch crops did not significantly affect yield. The use of catch crops interacts with other management factors, including row spacing and weed control, and this may have contributed to the negligible effects of catch crops. There was considerable variation in the amount of N (100–600 kg N ha^?1 year^?1) accumulated in the mulched grass–clover cuttings prior to ploughing and sowing of the winter wheat. This was reflected in grain yield and grain N uptake. Manure application to the cereals in the rotation reduced N accumulation in grass–clover at two of the locations, and this was estimated to have reduced grain yields by 0.1–0.2 Mg DM ha^?1 depending on site. Model estimations showed that the average yield reduction from weeds varied from 0.1 to 0.2 Mg DM ha^?1. The weed infestation was larger in the manure treatments, and this was estimated to have reduced the yield benefit of manure application by up to 0.1 Mg DM ha^?1. Adjusting for these model-estimated side-effects resulted in wheat grain yields gains from manure application of 0.7–1.1 Mg DM ha^?1.The apparent recovery efficiency of N in grains (N use efficiency, NUE) from NH₄–N in applied manure varied from 23% to 44%. The NUE in the winter cereals of N accumulated in grass–clover cuttings varied from 14% to 39% with the lowest value on the coarse sandy soil, most likely due to high rates of N leaching at this location. Both NUE and grain yield benefit in the winter cereals declined with increasing amounts of N accumulated in the grass–clover cuttings. The model-estimated benefit of increasing N input in grass–clover from 100 to 500 kg N ha^?1 varied from 0.8 to 2.0 Mg DM ha^?1 between locations. This is a considerably smaller yield increase than obtained for manure application, and it suggests that the productivity in this system may be improved by removing the cuttings and applying the material to the cereals in the rotation, possibly after digestion in a biogas reactor.Cereal grain protein content was increased more by the N in the grass–clover than from manure application, probably due to different timing of N availability. Green-manure crops or manures with a relatively wide C:N ratio may therefore be critical for ensuring sufficiently high protein contents in high yielding winter wheat for bread making.     

The influence of crop sequence on fungicide and herbicide use intensities in North German arable farming

The reduction of pesticide use intensity is a societal and political ambition. Crop rotation is one important method to control pests and diseases in arable farming. We investigated the contribution of crop rotation to the variability of herbicide and fungicide use of 60 farms in four regions of Northern Germany. Our study aimed at answering the question: do diverse crop sequences lead to reduced herbicide and fungicide use in arable farming?Ten-year data on chemical plant protection measures and field management were examined for six field crops. We classified crop sequences (triplets of three succeeding crops) according to their susceptibility for weeds and diseases (= ’riskiness’). The Treatment Frequency Index (TFI) of the last crop in the triplet was set in relation to the crop triplet riskiness, additionally also in combination with tillage.In general, herbicide and fungicide use intensities were smaller in more diverse crop sequences. Diversified cereal sequences, involving roots and tubers, maize or spring cereals were less dependent on herbicides. Cultivation of maize in three subsequent years increased herbicide use. Crop sequences including high proportion of winter cereals increased fungicide use in cereals, while roots and tubers, winter oilseed rape and set-aside in the crop sequence decreased it. In winter oilseed rape, sequences with roots and tubers also increased fungicide use. In sugar beets, sequences with maize or a high concentration of sugar beets led to increasing fungicide use. If farmers chose riskier crop sequences tillage by plough decreased the need for herbicide and fungicide use.To reduce herbicide and fungicide use intensities we recommend increasing the diversity of crop rotations, including a higher number of crops per rotation together with ploughing. Simplifying both crop sequence diversity and tillage intensity implies higher use of herbicides and fungicides. Results will be useful for convincing farmers to diversify crop sequences.     

Cereal yield and quality as affected by nitrogen availability in organic and conventional arable crop rotations: A combined modeling and experimental approach

The effects of nitrogen (N) availability related to fertilizer type, catch crop management, and rotation composition on cereal yield and grain N were investigated in four organic and one conventional cropping systems in Denmark using the FASSET model. The four-year rotation studied was: spring barley–(faba bean or grass-clover)–potato–winter wheat. Experiments were done at three locations representative of the different soil types and climatic conditions in Denmark. The three organic systems that included faba bean as the N fixing crop comprised a system with manure (stored pig slurry) and undersowing catch crops (OF + C + M), a system with manure but without undersowing catch crops (OF ? C + M), and a system without manure and with catch crops (OF + C ? M). A grass-clover green manure was used as N fixing crop in the other organic system with catch crops (OG + C + M). Cuttings of grass-clover were removed from the plots and an equivalent amount of total-N in pig slurry was applied to the cropping system. The conventional rotation included mineral fertilizer and catch crops (CF + C + F), although only non-legume catch crops were used. Measurements of cereal dry matter (DM) at harvest and of grain N contents were done in all plots. On average the FASSET model was able to predict the yield and grain N of cereals with a reasonable accuracy for the range of cropping systems and soil types studied, having a particularly good performance on winter wheat. Cereal yields were better on the more loamy soil. DM yield and grain N content were mainly influenced by the type and amount of fertilizer-N at all three locations. Although a catch crop benefit in terms of yield and grain N was observed in most of the cases, a limited N availability affected the cereal production in the four organic systems. Scenario analyses conducted with the FASSET model indicated the possibility of increasing N fertilization without significantly affecting N leaching if there is an adequate catch crop management. This would also improve yields of cereal production of organic farming in Denmark.     

Interactive Effect of Sulphur and Nitrogen on the Oil and Protein Contents and on the Fatty Acid Profiles of Oil in the Seeds of Rapeseed (Brassica campestris L.) and Mustard (Brassica juncea L. Czern. and Coss.)

In long-term field experiments on loamy sand and sandy loam, legumes (pea and lupine) stimulated microbial activity in the rhizosphere more than cereals (winter rye, winter wheat and spring barley), maize and oil flax. In the rhizosphere of winter wheat and maize, microbial activity and the bacteria species Pseudomonas , Agrobacterium and Xanthomonas were more stimulated by organic manuring than by mineral fertilization. A positive correlation between the stimulated bacteria species and the growth of young plants was found. Various mineral nitrogen applications had no influence on the rhizosphere microflora. The leghemoglobin content of pea nodules – an indicator of nitrogen fixation activity – was reduced by high nitrogen application in crop rotation.     

Effect of preceding crop combination and N fertilization on yield of six oil-seed rape cultivars (Brassica napus L.)

Information about the effect of the cropping history on the seed yield of oil-seed rape is extremely scarce. In 1992/93 and 1994/95, the effects of different preceding crop combinations (winter barley and winter wheat as preceding crops, oil-seed rape and wheat as pre-preceding crops) on the yield of six double low oil-seed rape cultivars were examined in a field trial at Hohenschulen Experimental Farm, north-west Germany. In addition, eight nitrogen treatments (different amounts and distribution patterns) were tested for their potential to reduce negative effects of the preceding crops. Following the cropping sequence of oil-seed rape then wheat, oil-seed rape yielded only 3.12 t ha⁻¹; after oil-seed rape then barley, the yield was 3.43 t ha⁻¹ compared with 3.77 t ha⁻¹ following wheat then barley and 3.71 t ha⁻¹ following wheat then wheat. The number of seeds per m² showed a similar pattern, whereas the thousand-seed weight partly compensated for the reduced seed number. It was highest if oil-seed rape was grown 2 years previously. The cultivars differed significantly in their yield potential. Express (3.79 t ha⁻¹) yielded 0.6 t ha⁻¹ more than Falcon (3.18 t ha⁻¹). Increasing amounts of fertilizer-N (80–200 kg N ha⁻¹) increased the seed yield from 3.21 t ha⁻¹ to 3.84 t ha⁻¹. Changes in the distribution pattern within one fertilizer amount had no effect on seed yield. In addition, no interactions between preceding crop combination and the different cultivars or N treatments occurred. It is concluded that crop management cannot totally eliminate the negative effects of an unfavourable cropping history on the seed yield of oil-seed rape.     

Die Ertragsentwicklung von Wintergetreide und Zuckerrüben bei dauerhafter Senkung des N-Düngungsniveaus

Effects of Long-term Fertilizer N Reduction on Winter Grain and Sugar Beet Yields
The results of recent field experiments concerning the effect of long-term N-reduction on the yield and quality of sugar beet, winter wheat and winter barley on plots which had previously had received ample amounts of N are studied in this paper.
The yield and quality of crops harvested on plots where N-dressings had been reduced for 6–8 years were similar to those of crops grown on plots where N-application had been reduced for only 1 year. Grain yield of winter wheat and winter barley grown without any N-application decreased to about 60 % of amounts normally harvested under local conditions with recommended N dressings, whereas the white sugar yield still remained at 90 %. The yields decreased slightly with an increase in the duration of the experiments. Yields of both cereals and beets remained constant within each level of fertilization, even 6 years after inition of trials with 50, 75 and 125 % of locally recommended N dressings.
On plots that did not receive nitrogen fertilization, N-contents of grain were between 1.5 and 1.7 % for winter wheat and 1.0 and 1.6 % N for winter barley. These contents remained constant over a trial period of 6 years. The amount of annual export of 55–91 kg N/ha also remained constant. Limited N availability causes a decrease in grain protein content rather than in grain yield.
Compared to winter grain species, sugar beet (with 74–117 kg N/ha in the beet body) could realize the highest annual export of nitrogen from the plot. Differences in annual N export existing between the various locations of the plots cannot be explained by differences in soil quality. Continuous high yields that were found even without any N-dressings may be explained by asymbiotic N-fixation, deposition of atmospheric N and a progressive decrease in soil N with 17–56 kg N/ha removed from soil resources annually.     

不同前茬对烤烟生长、产量和质量的影响

以烤烟K326品种为材料,在石林和寻甸两个不同气候生态点通过田间试验研究了一年两熟条件下油菜、小麦、大麦、绿肥和休闲5种前茬对烟株生长及烟叶产量、质量的影响。结果表明,不同前茬明显影响烟株的生长、成熟、产量、产值和评吸质量,且因生态区不同而有差异。前茬为小麦,两个试点烤烟均表现出前期生长较快、后期落黄较好;前茬为绿肥,烤烟前期生长较慢、后期生长过旺、落黄较迟;前茬为绿肥或休闲地,两试点烤后烟叶产量最高;但产值在石林点则以前茬为大麦、绿肥或油菜,寻甸点以前茬为大麦、绿肥或小麦的处理为最好。烟叶评吸质量在石林以油菜或小麦为前茬、寻甸以小麦或绿肥为前茬的处理最佳。综合而言,烟株生长期间气温较高的石林烟区烤烟前茬以油菜为宜,而气候冷凉的寻甸烟区则以小麦或绿肥为最佳前茬。     

The Effect of Improved Management on the Yield and Nitrogen Content of Legume Hay/Barley Crop Rotations in West Asia

In the light of growing governmental support in west Asia and north Africa for policies which either discourage cereal monoculture or encourage fallow replacement by farmers, two experiments were conducted in northern Syria. These were designed to evaluate and quantify the effect of agronomic interventions on the productivity and nitrogen content of legume hays, and the subsequent residual effects of these interventions on the yield and nitrogen content of a following barley crop. Quantitative estimates of the residual effects of legume hays, when grown under rainfed conditions, on the N uptake of barley are rarely available for the region at large.
The major management effects on the productivity of legume hays were the addition of phosphate fertilizer and a reduction in row spacing. Positive residual effects on the yields of following barley crops were shown to be small but not insignificant. They could be considered to be important influences in the sustained production of barley in legume hay-barley crop rotations.
It is suggested that the results give further positive evidence that farmers in west Asia will not resist the introduction of improved crop rotations including legumes in place of their current fallow-barley or continuous barley crop sequences.     

Crops and Pasture Rotations at Coonalpyn, South Australia: Effects on Nutrients in Wheat and Barley

A crop rotation experiment was conducted at Coonalpyn, South Australia from 1976–1979 on a deep red duplex soil. The experiment studied the effects of grain legumes, pasture or cereal in the previous season on the yield and nutrient content of wheat and barley. Yields, disease assessments, soil nitrogen and water conditions were reported previously. Cereals following grain legumes generally absorbed more of all the nutrients studied, N, P, K, S, Cu, Zn, Mn, than did cereals after pasture; cereal following cereal was generally intermediate. Effects on barley were similar to those on wheat except that wheat took up much more Cu and Mn. Uptake of all nutrients was increased by rainfall, which was greatest in 1979 and least in 1977, but concentrations were often decreased by rainfall. The effects on nutrient concentrations were variable and smaller than on uptake, except for N, Cu and Mn which were much enhanced by grain legumes as the previous crop. Concentrations of trace elements were generally low, being lowest for Cu in 1977, for Zn in 1978 and for Mn in 1979, particularly in barley. Uptake was lowest in 1977, the driest year, especially for Cu. An attempt was made to relate the seasonal effects on levels of trace elements to the pattern of disease incidence.     

Einfluß von Monoethanolamin auf den Ertrag von Kulturpflanzen

Effect of monoethanolamine on yield of crops
I. Studies on the effect of monoethanolamine on the grain yield and the nitrogen household in cereal plants (pot experiments)
The effect of monoethanolamine (EA, applied as foliar spray, 10 mg per pot) on grain yield and yield components was investigated in pot experiments with spring barley, winter wheat, and winter rye. Under conditions of a moderate drought stress the applied EA increased the grain yield of spring barley from 5 % to 7 % (significance only at α= 0.05). A stimulating effect of EA on the grain yield of winter wheat and winter rye was also obtained.
The positive influence of EA on the grain yield of spring barley was reproducible under the conditions of a limited water supply in small-scale plot experiments (increase of yield about 9 %).
In case of spring barley and winter rye the increase of the grain yield by EA, applied at growth stage 31 (= DC 31) was connected with a greater number of ear-bearing tillers. The increase of the winter wheat yield resulted from more grains per ear of the tillers.
The enhanced formation of tiller grain mass and total tiller biomass by EA was in correlation with a higher nitrogen import into tillers (r = 0.8⁺). Since an export of N from the main shoots into the tillers was not observed a higher N uptake (≥ 6 %) was calculated from N balances. After a fertilization with ¹⁵N-labelled fertilizers the additional ¹⁵N uptake was 13 % to 20 %.
Possible stress reducing activities caused by EA are discussed.     

Einfluß langjähriger Winterweizen-Monokultur auf Ertragsbildung, Krankheitsbefall und Nematodenbesatz im Vergleich zum Winterweizenanbau in der Fruchtfolge

Influence of winter wheat grown continuously on grain yield, foot rot infection and nematodes compared with winter wheat in rotation
The field trial, started in 1968 at the experimental-station in Rauischholzhausen, was intended to give informations about winter wheat in continuous cultivation. The question was if intensification of growing culture enables monoculture wheat to yield as high as winter wheat in rotation (sugar-beet, winter wheat, spring barley). Influence of green manuring with additional nitrogen, straw manuring with additional nitrogen, straw burning and fungicid treatment against eyespot was investigated.
The following results have been obtained in the years 1969 to 1985:
1. In the 17 years average winter wheat in rotation yielded with 50.1 dt/ha a higher amount of grain dry weight than wheat in monoculture (43.6 dt/ha). Only in 3 years wheat in monoculture reaches the grain yield level of wheat in rotation.
2. The incidence of Pseudocercosporella herpotrichoides was in wheat after wheat about 10% higher than in wheat after sugar-beets.
3. The use of fungicides against culm base diseases caused in monoculture an increase in yield of about 2.7 dt/ha which was not higher than in rotation (+2.5 dt/ha).
4. The first 12 years indicated a decline-effect with continuously decreasing differences in the yield of wheat in monoculture compared with rotation. But until the 17th year of the trial grain yield differences were as high as in the beginning.
It is not possible either by means of intensification of fertilizing or chemical plant protection treatment to reach the grain yield level of winter wheat in rotation with winter wheat in monoculture. Even the use of modern agronomical methodes remains crop rotation as a central part of an effective plant culture.