Effects of previous cropping on seed yield and yield components of oil-seed rape (Brassica napus L.)

Information about the effect of the preceding crop or crop combination on the seed yield of oil-seed rape is extremely scarce. Experiments were carried out in northwest Germany to investigate the effect of different preceding crops on the growth, seed yield and yield components of oil-seed rape. The two directly preceding crops, wheat and oil-seed rape, had only a negligible and non-significant effect on the seed yield of the following oil-seed rape crop. Oil-seed rape grown after wheat had more pods per plant, due to an increase in the number of pods on the higher category branches. In contrast, the seed yield and yield components were more affected by the cropping sequence, i.e. the crops 2 years before. Averaged over two experimental years, the greatest yields were observed in oil-seed rape following the sequence peas-wheat (694 g m⁻²), whereas the smallest seed yield occurred after 2 years of oil-seed rape cropping (371 g m⁻²). The differences in the seed yield were again associated with more pods per plant, which compensated for the lower number of plants m⁻², whereas the number of seeds per pod and the mean seed weight were almost unaffected by the previous cropping. It was not possible to relate the described differences to the crop development, since differences in the biomass caused by the previous cropping were only significant at maturity. Oil-seed rape grown after 2 years of oil-seed rape had the highest ratings of stem canker (Leptosphaeria maculans) as well as verticillium wilt (Verticillium dahliae). But the general level of the diseases was low, and therefore other causes for the effects described must be considered.     

The effect of lupins as compared with peas and oats on the yield of the subsequent winter barley crop

New high yielding early maturing cultivars of lupins have been introduced in north-west Europe as grain protein crops in crop rotations. This paper reports on a comparative study of lupins with peas and oats, and of their effect on yield of subsequent winter barley crops. These crops were given five levels of N under irrigated and non-irrigated conditions on sand and loam. Under rain fed conditions the grain yield of pea, oat and lupin varied between 24–36, 34–53 and 18–37 hkg DM ha⁻¹, respectively. Supplemental irrigation raised grain yield of oat to 50–60 hkg DM ha⁻¹, while grain yield in pea was not affected and grain yield in lupin in most cases decreased due to gray mould attack and excessive vegetative growth in the indeterminate lupin variety. Under rain fed conditions, the grain nitrogen content of pea, oat and lupin varied between 137–172, 61–80 and 189–226 kg N ha⁻¹, respectively, and was significantly higher in lupin as compared with pea. On sandy soil, similar low-root densities were found for pea, oat and lupin below 30 cm depth. On sand, at final harvest the residual soil-N of lupin and pea, as measured in a subsequent winter barley crop not supplied with N fertilizer, was 15 and 8–10 kg N ha⁻¹ higher than in winter barley following oat, respectively. The nature of the probably more N-root residues of lupin is discussed. On loam, the residual N of lupin and pea was similar, 18–27 kg N ha⁻¹. On sand, under rain fed conditions preceding lupin and pea as compared with oat, increased the barley grain yield at zero N-application 77 and 49%, respectively; the effect of lupin was significantly higher than that of pea until the highest N-level 120 kg N-application ha⁻¹. On loam under rain fed conditions preceding lupin and pea increased the barley grain yield at zero N-application by 36 and 62%, respectively, as compared with oat; at N-application>60 kg N ha⁻¹ the grain yield was similar after all three crops. For both soil types the same level of effect was found under irrigated conditions. Conclusions: Supplemental irrigation might result in lower grain yield in lupin due to gray mould attack and excessive growth if indeterminate lupin varieties are used. Grain nitrogen yield of lupin is significantly higher than that of pea. On sand, the effect of lupin on the subsequent winter barley grain yield is significantly higher than that of pea, probably due to greater N-root nitrogen residues. On loam, lupin and pea have similar effects on the subsequent winter barley crop.     

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.     

Yield-rainfall relationships in cereal cropping systems in the Ebro river valley of Spain

Wheat and barley yields from three farms in the Ebro river valley are shown to be strongly dependent on seasonal rainfall, particularly that during November-January and March-May of the cropping season. In the driest farm, in Monegrillo, Zaragoza province (seasonal rainfall, 251 mm), yields increased by c. 5.9 (wheat) and 9.4 (barley) kg ha⁻¹ per mm of extra rain during the entire cropping season, taken as October-May inclusive. The other farms, at El Canós and Selvanera in Lleida province, had seasonal rainfalls of 364 and 334 mm, and yields of barley increased by 4.3 and 9.0 kg ha⁻¹, respectively, per mm of extra rain in the cropping season, taken as September to May inclusive.

In Monegrillo, cereals are grown in a cereal-fallow rotation. Normal fallowing (duration 17 months) compared to minimum fallowing (5 months) increased the calculated water content of the top 100 cm of the dominant soils by 19 mm. This extra water was estimated to benefit yield by 7.0% (wheat) and 6.2% (barley), raising the average yields of crops greater than 300 kg ha⁻¹ to 1222 and 1522 kg ha⁻¹, respectively. Agronomic practices in Monegrillo during the fallow should focus on means of increasing the proportion of the rain stored in the profile during the fallow. At all three locations, decreasing water evaporation from the soil during the cropping season would likely benefit yield.     

Simulating winter wheat yields under temperate conditions: exploring different management scenarios

This paper describes a methodology for analysing management strategies to find best agronomic practices using a crop simulation model (CERES-Wheat). The study area is the estate of Imperial College at Wye, in the Stour Catchment, Kent, UK, an area highly suited to winter wheat production. The model is validated using historic crop performance data. Yield responses to differing sowing rates (range 200–450 seeds m⁻²), sowing dates and rates of nitrogen application (between 100 and 220 kg ha⁻¹) with soil types of medium to heavy texture were simulated under water-limited conditions using historical daily weather data. In model validation, observed yields ranged between 6.9 and 7.4 t ha⁻¹, while simulated ranges were between 6.9 and 7.8 ha⁻¹. The RSMD of the difference was small (0.24 t ha⁻¹) and non-significant. Optimum management practices (in terms of planting date, seed density and nitrogen application) were thereby defined. Also, simulations of potential yield (i.e. yield with no water and nutrient stress) were run for comparison. Results of this study reveal that the calibrated and validated CERES-Wheat model can be successfully used for the prediction of wheat growth and yield under conditions appropriate to Western Europe.     

Effect of varied N rates and N timings on yield, N uptake and fertilizer N use efficiency of a six-row and a two-row winter barley

The effects of N rates and N timings on yield formation, N uptake at five growth stages and fertilizer N use efficiency of six-row and two-row winter barley were evaluated in field trials conducted from 1990/91 to 1992/93 at the TU Munich's research station Roggenstein.

On average over 3 years the six-row cultivar yielded most at a total rate of 110 kg ha⁻¹ N including an early application of 40 kg ha⁻¹ N up to EC 30 (Zadoks scale). The two-row cultivar achieved maximum yield at a total rate of 140 kg ha⁻¹ N including early applications of 70 kg ha⁻¹ N up to EC 30. The highest yielding N-treatments of six-row barley regularly took up less nitrogen at EC 32 (95 kg ha⁻¹ N on average) than the non-optimally fertilized treatments, whereas full exploitation of the yield potential of two-row barley was associated with higher rates of N-uptake at EC 32 (113 kg ha⁻¹ N on average).

Lodging did not occur in the trials conducted in 1991 and 1992 and no difference was detected between the two cultivars in fertilizer N use efficiency. With six-row barley the N treatment giving maximum yield also led to an optimum fertilizer N use efficiency. Full exploitation of the two-row barley yield potential was associated with suboptimal fertilizer N use efficiencies.     

Residual nitrogen effect of clover-ryegrass swards on yield and N uptake of a subsequent winter wheat crop as studied by use of N methodology and mathematical modelling

The residual effect of 2-year-old swards of clover-ryegrass mixture and ryegrass in monoculture on yield and N uptake in a subsequent winter wheat crop was investigated by use of the ¹⁵N dilution method and by mathematical modelling. The amount of N in the wheat crop, derived from clover-ryegrass residues was 25–43% greater than that derived from residues of ryegrass which had been growing in monoculture. Expressed in absolute values, the N uptake in the subsequent winter wheat crop was 23–28 kg N ha ⁻¹ greater after clover-ryegrass mixture than after ryegrass in monoculture. Up to about 54 kg N ha⁻¹ of the N mineralised from the clover-ryegrass crop was calculated to be leached, whereas only 11 kg N ha⁻¹ was leached following ryegrass in monoculture.     

Biomass yield and energy balance of giant reed (Arundo donax L.) cropped in central Italy as related to different management practices

In order to evaluate the possibility of reducing energy input in giant reed (Arundo donax L.) as a perennial biomass crop, a field experiment was carried out from 1996 to 2001 in central Italy. Crop yield response to fertilisation (200–80–200 kg ha⁻¹ N–P–K), harvest time (autumn and winter) and plant density (20,000 and 40,000 plants per ha) was evaluated. The energy balance was assessed considering the energy costs of production inputs and the energy output obtained by the transformation of the final product. The crop yield increased by +50% from the establishment period to the 2nd year of growth when it achieved the highest dry matter yield. The mature crop displayed on average annual production rates of 3 kg dry matter m⁻², with maximum values obtained in fertilised plot and during winter harvest time.

Fertilisation mainly enhanced dry matter yield in the initial period (+0.7 kg dry matter m⁻² as years 1–6 mean value). The biomass water content was affected by harvest time, decreasing by about 10% from autumn to winter. With regard to plant density, higher dry matter yields were achieved with 20,000 plants per ha (+0.3 kg dry matter m⁻² as years 1–6 mean value).

The total energy input decreased from fertilised (18 GJ ha⁻¹) to not fertilised crops (4 GJ ha⁻¹). The higher energetic input was represented by fertilisation which involved 14 GJ ha⁻¹ (fertilisers plus their distribution) of total energy costs. This value represents 78% of total energy inputs for fertilised crops.

Giant reed biomass calorific mean value (i.e., the calorific value obtained from combustion of biomass sample in an adiabatic system) was about 17 MJ kg⁻¹ dry matter and it was not affected by fertilisation, or by plant density or harvest time. Fertilisation enhanced crop biomass yield from 23 to 27 dry tonnes per ha (years 1–6 mean value). This 15% increase was possible with an energy consumption of 70% of the overall energy cost. Maximum energy yield output was 496 GJ ha⁻¹, obtained with 20,000 plants per ha and fertilisation. From the establishment period to 2nd–6th year of growth the energy production efficiency (as ratio between energy output and energy input per ha) and the net energy yield (as difference between energy output and energy input per ha) increased due to the low crop dry biomass yield and the high energy costs for crop planting. The energy production efficiency and net energy yield were also affected by fertilisation and plant density. In the mature crop the energy efficiency was highest without fertilisation both with 20,000 (131 GJ ha⁻¹) and 40,000 plants per ha (119 GJ ha⁻¹).     

Yield and quality components of silage maize in killed and live cover crop sods

In sloping areas with high precipitation, planting maize into live winter cover crop sods may help to alleviate the environmental problems associated with clean-tillage production systems of maize. The present study evaluates the performance of silage maize (Zea mays L.) under several cultivation methods: CC (conventional cropping system, i.e., maize was sown into the bare, autumn-ploughed soil); LGS/CK (maize was planted into a living Italian ryegrass (Lolium multiflorum Lam.) sod which was subsequently herbicidally killed); and LGS/MR (similar to LGS/CK, but the ryegrass was mechanically regulated). The research was conducted in the midlands of Switzerland on a fertile sandy loam under humid conditions during three cropping seasons. With 110 kg N ha⁻¹ (fertilizer nitrogen plus mineral nitrogen of the soil at maize planting), the CC system was much more productive than were the LGS/CK and LGS/MR systems in terms of dry matter and nitrogen yields of maize. Increasing the nitrogen supply to 250 kg N ha⁻¹ considerably reduced the yield advantage of CC over the LGS/CK and LGS/MR systems, indicating that nitrogen was the most limiting factor for maize yield in the mulch seeding systems. With 250 kg N ha⁻¹, the LGS/CK and LGS/MR systems produced greater total yields of digestible organic matter (maize plus ryegrass) than did the CC system, whereas the total nitrogen yield was similar for all cropping systems. The whole-shoot concentrations of nitrogen were highest under CC, irrespective of the level of nitrogen supply. With 110 kg N ha⁻¹, concentrations of phosphorus and magnesium were clearly higher for the mulch seeding systems. There were only minor differences among the cropping methods in the concentrations of potassium and calcium in the whole shoot. When 250 kg N ha⁻¹ were applied, there were no significant variations among the cropping systems in the concentrations of minerals. Changes in the botanical composition of the cover crop sod and in the time and method of cover crop control may help to reduce the competition for nitrogen between maize and the living mulch.     

Tillage, cover crops, and nitrogen fertilization effects on soil nitrogen and cotton and sorghum yields

Sustainable soil and crop management practices that reduce soil erosion and nitrogen (N) leaching, conserve soil organic matter, and optimize cotton and sorghum yields still remain a challenge. We examined the influence of three tillage practices (no-till, strip till and chisel till), four cover crops {legume [hairy vetch (Vicia villosa Roth)], nonlegume [rye (Secaele cereale L.)], vetch/rye biculture and winter weeds or no cover crop}, and three N fertilization rates (0, 60–65 and 120–130 kg N ha⁻¹) on soil inorganic N content at the 0–30 cm depth and yields and N uptake of cotton (Gossypium hirsutum L.) and sorghum [Sorghum bicolor (L.) Moench]. A field experiment was conducted on Dothan sandy loam (fine-loamy, siliceous, thermic, Plinthic Paleudults) from 1999 to 2002 in Georgia, USA. Nitrogen supplied by cover crops was greater with vetch and vetch/rye biculture than with rye and weeds. Soil inorganic N at the 0–10 and 10–30 cm depths increased with increasing N rate and were greater with vetch than with rye and weeds in April 2000 and 2002. Inorganic N at 0–10 cm was also greater with vetch than with rye in no-till, greater with vetch/rye than with rye and weeds in strip till, and greater with vetch than with rye and weeds in chisel till. In 2000, cotton lint yield and N uptake were greater in no-till with rye or 60 kg N ha⁻¹ than in other treatments, but biomass (stems + leaves) yield and N uptake were greater with vetch and vetch/rye than with rye or weeds, and greater with 60 and 120 than with 0 kg N ha⁻¹. In 2001, sorghum grain yield, biomass yield, and N uptake were greater in strip till and chisel till than in no-till, and greater in vetch and vetch/rye with or without N than in rye and weeds with 0 or 65 kg N ha⁻¹. In 2002, cotton lint yield and N uptake were greater in chisel till, rye and weeds with 0 or 60 kg N ha⁻¹ than in other treatments, but biomass N uptake was greater in vetch/rye with 60 kg N ha⁻¹ than in rye and weeds with 0 or 60 kg N ha⁻¹. Increased N supplied by hairy vetch or 120–130 kg N ha⁻¹ increased soil N availability, sorghum grain yield, cotton and sorghum biomass yields, and N uptake but decreased cotton lint yield and lint N uptake compared with rye, weeds or 0 kg N ha⁻¹. Cotton and sorghum yields and N uptake can be optimized and potentials for soil erosion and N leaching can be reduced by using conservation tillage, such as no-till or strip till, with vetch/rye biculture cover crop and 60–65 kg N ha⁻¹. The results can be applied in regions where cover crops can be grown in the winter to reduce soil erosion and N leaching and where tillage intensity and N fertilization rates can be minimized to reduce the costs of energy requirement for tillage and N fertilization while optimizing crop production.     

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.     

Population dynamics of volunteer oilseed rape (Brassica napus L.) affected by tillage

Volunteer plants of oilseed rape (Brassica napus L.) from persistent seeds in soil can affect subsequent crops. Apart from the agricultural disadvantages, the environment and the marketing of the seeds may also be affected, particularly if plants with special ingredients or genetically modified (gm) plants are grown. In order to investigate the influence of soil cultivation and genotype on seed persistence and gene flow via volunteers, a field experiment was set up testing four tillage treatments and two cultivars in a split-plot design. The cultivars tested were near-isogenic to two gm cultivars. To simulate harvesting losses, 10 000 seeds m⁻² were broadcast on a soil in July. The subsequent tillage treatments were combinations of immediate or delayed stubble tillage by a rotary tiller, primary tillage with plough or cultivator, or zero tillage. Over the following year, the fate of the seeds was determined. Immediate stubble tillage with following cultivator or plough resulted in 586 resp. 246 seeds m⁻² in the soil seed bank. After delayed stubble tillage with following plough, 76 seeds m⁻² were found, and no soil seed bank was built up in the zero tillage treatment. Nevertheless, in the zero tillage treatment, several robust volunteer plants survived the herbicide application before the direct drilling in autumn until following spring. In the zero tillage treatment and in the cultivator treatment, 0.19 volunteers m⁻² resp. 0.06 volunteers m⁻² flowered simultaneously to ordinarily sown oilseed rape in the following crop of winter wheat and produced 73 resp. 18 seeds m⁻². Delayed stubble tillage reduced the risk of gene escape via the soil seed bank, while zero tillage resulted in the highest risk of gene escape by pollen and by production of a new generation of seeds. In terms of a labelling threshold for gm food this number of seeds would be below the threshold of 0.9% of transgenic parts in conventially bred food or feed.     

Nutrient surpluses on integrated arable farms

From 1990 to 1993 nutrient fluxes were monitored on 38 private arable farms that had adopted farming strategies aiming at reduced nutrient inputs and substitution of mineral fertilizers by organic fertilizers. The nutrient surplus was defined as the difference between inputs (including inputs through deposition, seeds and biological fixation) and outputs in crop products, and amounted to 117 kg nitrogen (N), 14 kg phosphorus (P) and 21 kg potash (K) ha⁻¹ year⁻¹ on average. Potato and sugar beet had relatively high nutrient surpluses resulting both from crop characteristics and the use of organic manure. The surplus varied markedly among farms due to differences in cropping frequency, fertilizer inputs and crop outputs. Averaged over the years, ca. 70% of the participants achieved surpluses below 150 kg N, 20 kg P and 50 kg K ha⁻¹ year⁻¹.

The amounts of residual soil mineral N (RSMN) exceeded those normally found in field experiments except for data collected after the wet summer of 1993. Distinct differences between crops were observed. Only in the case of potato a significant relationship was observed between the effective N input and RSMN. On a whole-farm level, RSMN amounted to more than 70 kg ha⁻¹ N on 77, 74, 87 and 18% of the farms in the consecutive years.     

Long-term fate of nitrogen uptake in catch crops

The long-term effects of undersowing a ryegrass catch crop in cereals was analysed with the FASSET simulation model. The model was tested on a 28-year field experiment with ryegrass catch crops in spring barley. The experiment included treatments with nitrogen (N) fertiliser rates, catch crop use and timing of tillage. The modelled effects of these treatments generally agreed with observations on crop production, soil carbon, soil nitrogen and nitrate leaching. Both the observations and the simulations predicted a yield increase of 7 kg N ha⁻¹ and an increase in nitrate leaching of 13 kg N ha⁻¹ due to a prehistory of 24 years with continuous use of catch crops compared to a prehistory without catch crops.

A range of scenarios was constructed to evaluate the fate of the reduced nitrate leaching on crop N uptake, N leaching, gaseous emissions and change in soil organic N, and how this fate interacts with soils and climate and management. These scenarios showed that 22–30% of the reduced nitrate leaching was subsequently leached during the following decades after termination of catch crop use. Between 35 and 40% of the reduced nitrate leaching was harvested in cereals. The exact distribution depended primarily on the soil texture. The scenarios showed that effects of catch crops should be evaluated on the long-term rather than consider short-term effects only.     

Effect of Foliar Applications of Glycinebetaine on Stress Tolerance, Growth, and Yield of Spring Cereals and Summer Turnip Rape in Finland

Crop losses caused by environmental stresses might be reduced by applying osmoprotectans to crop canopies. Glycinebetaine is endogenously accumulated by some halophytes under stress conditions and represents such a compound. Glycinebetaine was applied exogenously to barley ( Hordeum vulgare L.), oat ( Avena sativa L.), spring wheat ( Triticum aestwum L.), and summer turnip rape ( Brassica rapa ssp. oleifera DC.) canopies and its optimal concentration was monitored in the greenhouse. In field experiments the response of crop plants to betaine applications was assessed by measuring accumulation of above ground biomass, leaf area index (LAI), leaf chlorophyll, and yield. The optimum betaine concentration producing advantageous effects on growth and crop physiology in turnip rape was close to 0.1 M and for wheat 0.3 M. Such concentrations promoted accumulation of betaine similar to that of halophytes under stress conditions [ca. 200 μmol (g DM)⁻¹]. In the 1993 field experiment peak LAIs were recorded in irrigated wheat and barley treated with 17.5 kg ha⁻¹ betaine applied at 300 1 ha⁻¹. Green leaf area was slightly more persistent in wheat treated twice with 1 kg ha⁻¹ betaine applied at 200 1 ha⁻¹ in 1994, although it was not associated with increased grain yield. Our results indicated that betaine has no actual potential in Finland for the principal grain crops but further studies are needed in stress prone environments to assess the potential of betaine treatments for preventing crop failures.     

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

Yield formation in cereal-rich crop rotations and monocultures in an extensive and intensive crop-management system
In 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.     

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。     

Effects of Mediterranean climate on wheat bread-making quality

The unpredictability of the Mediterranean climate causes a large fluctuation in wheat yield and quality but offers the opportunity for the production of high quality wheats which are lacking in the European Union.

This paper describes the effects of nitrogen fertilization rate and timing on five Triticum aestivum L. cultivars differing in bread-making quality, cultivated in six representative Italian sites (years/locations). Nitrogen was applied at each location at two rates, the first corresponding to the amount estimated to maximize grain yield, the second 30% higher. Three timings of nitrogen applications were tested including a late application at the boot stage. Bread-making quality was evaluated with the Chopin alveograph and each sample was assigned to the following qualitative classes of the Italian market: Class 1, improver wheat; Class 2, for direct bread-making; Class 3, ordinary wheat.

Cultivars differed significantly in all agronomic and qualitative traits. Grain yield was highest in the northern location (7.1 t ha⁻¹) and lowest in the south of the Italian peninsula (2.61 ha⁻¹), while in Sicily abundant rains in both years enabled a yield of 6.41 ha⁻¹ to be obtained. As far as bread-making quality is concerned, the greatest proportion of grain samples belonging to Class 1 was obtained from the northern location. The year of cultivation strongly affected quality, particularly with regard to gluten tenacity, in all locations, though the quality ranking of the cultivars remained substantially stable across locations. Nitrogen applications greater than those considered optimal to maximize yield, combined with a better distribution during the life cycle, significantly improved bread-making quality.

It was concluded that high quality wheats can be obtained in a wide range of growing conditions in the Mediterranean climate. However the likelihood of genotype × environment interactions, statistically significant for both yield and quality, call for a more precise management of nitrogen fertilization in relation to the cultivars chosen and the climatic features of each site.     

Yields and N uptake of barley and ryegrass from soils with added animal manure differing in straw and urine content

Four types of cattle manure were prepared by mixing faeces with different ratios of urine + straw, one manure being faeces without straw and urine. Following 3 to 6 months of storage, the manures were applied in spring or autumn to a sandy loam and a coarse sand in amounts corresponding to 120 kg N ha⁻¹. Spring barley (Hordeum vulgare L.) undersown with perennial ryegrass (Lolium perenne L.) were used as test crops. Barley was harvested at maturity and the wintering ryegrass was cut three times in the second year. Additional mineral N in the form of ¹⁵N-labelled mineral fertilizer (50 kg N ha⁻¹) was added to all barley plots at planting in spring. Non-manured plots receiving only the ¹⁵N-labelled mineral fertilizer were included. Faeces without urine + straw contained more NH₄-N than the other manures and spring incorporation of this manure gave the highest dry matter yield and N uptake of the barley. When faeces without urine + straw was applied in autumn, the yield and N uptake were increased only on the sandy loam. On the coarse sand, the NH₄-N was probably leached as NO₃-N during the winter. The three manures with urine + straw did not affect barley grain yield or total N uptake. Thus these manures did not mineralize nor immobilize measurable quantities of N in the first growth period. On the sandy loam, the patterns of N uptake in ryegrass indicated an increased availability of manure N during the second growth period. The availability of N from the ¹⁵NH₄¹⁵NO₃ was similar in all plots when manures were applied in spring. Less ¹⁵N was taken up by the spring barley when manure was added in autumn compared with crops given ¹⁵NH₄¹⁵NO₃ only. Thus short-term effects of N in cattle faeces stored with or without straw + urine are low. For soils low in mineral N such manures may potentially reduce crop N uptake.     

Stickstoffaufnahme und Stickstoffrückstände von Hauptfrucht-und Ausfallrapsbeständen

Nitrogen Uptake and Nitrogen Residuals of Winter Oil-Seed Rape and Fallout Rape
The objective of the investigation was a study of the relationship between seed dry-matter production and vegetative dry-matter production in oil-seed rape crops and their dependence on the production conditions. In addition to the relationship between the N-uptake during the vegetation period and the N-residue after harvest was of major interest. Furthermore the potential for N-uptake in fallout rape was measured. Over two vegetation periods factorial field experiments with winter oil-seed rape, cv. Lirabon, different drilling techniques and different nitrogen fertilization levels were tested. Measured traits were: the dry-matter accumulation including root mass and fall-off leaf-material mass, the N-uptake of both the oil-seed crops and the fallout rape stands, and, simultaneously, the soil NO₃-N content. Finally the harvest indices and the N-harvest indices were calculated.
Combined with a N-uptake of up to 330 kg N/ha, oil-seed rape crops produced up to 200 dt dry matter/ ha. At seed yield levels of 33dt/ha (d.m.), harvest indices varied from 0.14—0.23 and N-harvest indices varied from 0.30–0.50. As a result of the residue of vegetative plant material at harvest, leaf losses before harvest and the soil NO₃-N-contents at harvest up to 275 kg N/ha remained in the field. After the harvest of oil-seed rape, the soil NO₃-N-contents were quickly reduced by emerging and growing fallout rape stands. However, following soil-preparation measures in the autumn, a continuous rise in the soil NO₃-N-content was observed.