Cereal Crop Rotation Research Articles

A method to determine the pollen-mediated spread of target-site resistance to acetylcoenzyme A carboxylase inhibitors in black grass (Alopecurus myosuroides Huds.)

In this study the spread of target-site resistance to ACCase inhibitors via pollen was characterized in a population of Alopecurus myosuroides. The spread of target-site resistance was assessed in a three-year model crop rotation experiment with 20 plots (round circles of 1 m diameter and enclosed by concrete walls of 50 cm height to avoid seed spread) in a total area of 90 m2. In one plot (so called initial plot) an A. myosuroides population with a known target-site resistance (Leu1781) was sown. A herbicide sensitive biotype (Ile1781) was sown in all others plots. In a cereal crop rotation the second and third crop were treated with field rate of fenoxaprop and leaf samples of surviving plants were taken for DNA analysis. The Pyrosequencing® technology was applied to determine the genotype of sensitive (Ile1781) heterozygous (Ile/Leu1781) and homozygous (Leu1781) individuals. Plants carrying a heterozygous target-site resistance outside the initial plot were a first indication for outcrossing via pollen between the plots. Results showed an outcrossing frequency of 0.4 to 3.3% of Leu1781 into wild-type (Ile1781). The maximal distance for outcrossing from the initial plot was 4 m and 37% of the plots were infested with resistant plants. The frequency of Leu1781 increased in the second year from 7.9 to 26.6% and most plots were infested with herbicide-resistant plants. Outcrossing events decreased with increasing distance from the initial plot. After the first application, all plants identified as resistant outside the initial plot were heterozygous, while homozygous resistant plants were detected in the second year and indicated inbreeding between and within the plots. The results obtained over two years demonstrate the strong potential of the study to model the spread of resistance via pollen in allogamous species in narrow spaces. Hence, we provide a method for obtaining data under conditions close to field conditions.

Recommendations for nutrient management plans in a semi-arid environment

A nutrient management plan (NMP) field experiment was conducted to investigate the fate of nitrogen (N), phosphorus (P), potassium (K) and salts in a semi-arid environment (San Jacinto, CA). Our mechanistic approach to study NMP performance was based on comprehensive measurements of water and N mass balance in the root zone. A cereal crop rotation (wheat-rye hybrid to sorghum, Triticum aestivum L.– Secale cereale L. to Sorghum bicolor L. Moench) that does not fix atmospheric N was employed during 2007, whereas a legume crop (alfalfa, Medicago sativa L.) that forms nodules to fix N was used in 2008. Blending (2007 and 2008) and cyclic (2007) dairy wastewater (DWW) application strategies (no statistical difference in 2007) were implemented to meet crop water and N uptake. The high content of salts in DWW and accurate application of water to meet evapotranspiration ( ET) yielded salt accumulation in the root zone. Leaching these salts after the fallow period resulted in the flushing of nitrate that had accumulated in the root zone due to continuous mineralization of soil organic N. This observation suggested that a conservative NMP should account for mineralization of organic N by (i) leaching salts following harvests rather than prior to planting and (ii) maintaining soils with low values of organic N. For the wheat-rye hybrid–sorghum rotation, losses of nitrate below the root zone were minimal and the soil organic N reservoir and P were depleted over time by applying only a fraction of the plant N uptake with DWW (28–48%) and using DWW that was treated to reduce the fraction of organic N (3–10%), whereas K accumulated similar to other salts. Conversely, with alfalfa approximately 15% of the applied N was leached below the root zone and the soil organic N increased during the growing season. These observations were attributed to fixation of atmospheric N, increased root density, and applying a higher fraction of plant N uptake with DWW (76%). Collectively, our results indicate that NMPs should accurately account for water and nutrient mass balances, and salt accumulation to be protective of the environment.

Seed alkaloid concentrations are not affected by agronomic and phosphorus-nutrition treatments that reduce Pleiochaeta setosa Hughes disease on narrow-leafed lupin (Lupinus angustifolius)

The severity of brown spot caused by the fungus Pleiochaeta setosa (Kirchn.) Hughes in narrow-leafed lupin (Lupinus angustifolius L.) is reduced by improving phosphorus (P) nutrition and using agronomic treatments that extend crop rotation or increase cereal stubble retention. The aim of this work was to investigate the impact of these treatments on the alkaloid concentrations of the harvested seed of 3 sweet cultivars of L. angustifolius that differed in their susceptibility to this fungal disease: Merrit (susceptible), Tallerack and Myallie (both moderately resistant). Because abiotic and biotic stresses appear to stimulate plant alkaloid biosynthesis, we hypothesised that higher levels of disease pressure may increase alkaloid concentrations in the harvested seed, particularly in the disease-susceptible Merrit. The main effects of P nutrition, cereal stubble retention, genotype and crop rotation were significant for the severity of brown spot and plant biomass of narrow-leafed lupin in a field trial in Wongan Hills, Western Australia, but were not significant for total alkaloid concentrations or the relative proportions of individual alkaloids of the harvested seed. Seed total alkaloid concentrations were in most cases below the maximum permitted concentration established for lupin seed (200 mg/kg dry matter) and were independent of the severity of brown spot on leaves. The great fluctuations of seed total alkaloid concentrations observed in grower deliveries to bulk handling facilities and in lupin cultivar yield testing trials are unlikely to result from the nutritional and agronomic treatments such as those investigated in this experiment, or the various disease levels that resulted from these treatments.

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.

Population dynamics of Rumex obtusifolius under contrasting lucerne cropping systems

The population dynamics of Rumex obtusifolius L. was analysed in a lucerne:winter cereal crop rotation by means of a matrix population model that takes into consideration two crop rotation periods: the lucerne (Medicago sativa L.) cropping period and the cereal cropping period. Several transition matrices based on life‐cycle stages were calculated for each cropping period using experimental data and were used in the construction of a model that analyses the population dynamics of R. obtusifolius under different harvest dates and lengths of lucerne cropping periods. Model projections showed that populations of R. obtusifolius increased during the lucerne cropping period regardless of harvest date and decreased during the cereal cropping period. Under a late harvest date, populations decreased at each crop rotation when lucerne was grown for 3 years, remained close to the equilibrium when lucerne was left to grow for 5 years, and increased for longer lucerne cropping periods. In contrast, populations of R. obtusifolius decreased even with a lucerne cropping period of 9 years under an early harvest date. The significance of these results in relation to the biology and the non‐chemical control of the species is discussed.

Ertragsbildung von getreidereichen Fruchtfolgen und Getreide‐monokulturen in einem extensiven und intensiven Anbausystem

AbstractYield formation in cereal‐rich crop rotations and monocultures in an extensive and intensive crop‐management systemIn a long duration trial, conducted from 1979/80 to 1992 at TU‐Munich's research station in Roggenstein, the performance of monocultures of winter wheat, winter barley and winter rye, as well as numerous cereal‐crop rotations were compared in an extensive and intensive crop‐management system. The results obtained can be summarized as follows.Over the course of 13 years, the influence of the immediately preceding crop on the yield of the main crops was of much greater significance than the rotation as a whole. With winter wheat, no yield differences could be observed between monoculture and cereal crop rotation (if the rotation did not include oats). Oats, rape, field bean, pea, potato and maize as preceding crops, however, in crop management systems, led to, on average, an increase in yield of 13 dt/ha from the following wheat. Winter barley yields were not significantly different in monoculture, cereal crop rotations and crop rotations containing 66% cereals. Furthermore, winter rye yields were the same in monocultures and cereal crop rotations. With all cereals, intensification of fertilizing and chemical plant protection led to a considerable increase in yield, but did not diminish the effects of the preceding crop. Hence, even with the use of modern agronomical techniques it is impossible to compensate for yield losses due to crop rotation.

Crop rotation with pure stands and mixtures of barley and wheat to control stem and root rot diseases

Crop rotations are known to be a natural barrier against a wide range of fungal soil-borne pathogens. Results shown in this paper are based on observations that were made in the third growing period of a 3-year cereal crop rotation (1989–1991). Mixtures as pre-crops and main crops were compared with pure stands of barley and wheat also grown as pre- and main crops. After this 3-year period, field experiments showed that interspecific mixtures of winter barley and winter wheat reduced stem rot caused by Pseudocercosporella herpotrichoides, Fusarium spp., Gaeumannomyces graminis and Rhizoctonia cerealis. Growing barley and wheat after a cereal mixture resulted in an increased number of healthy plant stems. The pre-crop mixture significantly reduced the disease incidence of Fusarium spp. on barley (> 50%) during stem elongation and ripening. Disease incidence of G. graminis on barley during ripening decreased from 44% after barley to 9% when grown after the mixture. Differences in take-all incidence on wheat due to different pre-crops were not significant. The percentage of P. herpotrichoides lesions on wheat grown in a mixture increased after pre-crops containing barley. Furthermore, interactions occurred between pathogens, indicating differences in competition. Additional effects on plant health were observed where barley-wheat mixtures were grown for 2 years. In general, the incidence of stem base diseases was lowest in mixtures that were grown after a mixture. Disease reductions on wheat grown in a mixture after a mixed pre-crop were comparable to those disease reductions brought about by chemical fungicides applied in pure stands of wheat. Pathogen frequency on wheat hypocotyl and root tissue was estimated using a selective medium: the frequency of G. graminis on wheat tissue decreased from 14% after the pre-crop barley and 7% after the pre-crop wheat, to 1% after the pre-crop mixture. The frequency of Fusarium spp. was generally not affected, but the spectrum of species changed quantitatively. A greater number of weak or non-pathogenic fungi were isolated from wheat segments when the plants were grown after a mixed pre-crop.

The occurrence of vesicular-arbuscular mycorrhiza in agro-ecosystems

In a long-lasting field experiment at the Research Station Hanninghof at Dulmen (Westphalia), laid out in 1971, the inoculum potential (IP) of vesicular-arbuscular mycorrhizal (VAM) fungi of soil from winter barley in a continuous monoculture (CM) and in a four-years cereal crop rotation (CR: winter wheat, winter barley, winter rye, oats) was estimated from 1980–1982. The influence of green manure and increased mineral N-fertilization (100 and 200 kg ha−1) on VAM-IP was also assessed. VAM-IP was high at both levels of N-application, although the higher N-fertilization resulted in a reduction of VAM-IP in winter barley — in CR as well as in CM. No influence of N-fertilization on VAM-IP was observed with oats and winter rye, which were only cultivated in CR. Green manure had a negative effect on IP in CM barley, but not in CR barley. This may be due to the annual applications of green manure in CM, while green manure in CR was only applied prior to the cultivation of oats and winter wheat, but not to winter barley. Except for the effects of green manure remarkable differences in VAM-IP were found neither in CR nor in CM of winter barley. This is also reflected in the yields of barley in CM and indicates the relative self-tolerance of winter barley.