摘要:

AbstractThe evolution of concepts and definitions of agricultural systems over time is presented. Inputs of an agricultural system are classified as components and activities. A component is either a resource or a technology. The activities are the management of resources and the application of technology in the production process. The outputs of a production process will include both the targeted product and the environmental impact. When these terms are used to describe an agricultural system graphically, the dynamic aspects of the system can easily be illustrated and problems associated with the system can be properly identified. Sustainable agriculture is recognized as conveying certain objectives or delineating certain requirements of an agricultural system, in terms of both the input and output of the system. These objectives are: (1) producing necessary quantity of high quality food and fiber; (2) profitable to the grower; (3) conserving nonrenewable resources; and (4) harmonious with biological, physical and social environments. These objectives have long‐term implications and attempt to secure the future viability of agriculture. Therefore they embrace the concept of sustainability. The difficulty of constructing such a system is that not all the objectives are compatible; compromise or trade‐offs among the objectives are often necessary in developing a workable sustainable system. Progress and improvement can always be made through research, but no perfect system can realistically be constructed. General research issues in sustainable agriculture are discussed. Priorities in developing appropriate technology based on sound biological principles and laws of physics and mechanics for pest and weed control are sugges

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1990.tb00837.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe harvest index Z is defined, for example for cereals, as the ratio between grain yield X and total yield Y: Z = X/Y. For individual measurements xiof X and yiof Y the individual harvest index is calculated by zi= xi/yi. These individual measurements i are based on N different experimental units (single plants, random samples from plots or total plots).Mean harvest indices are commonly calculated either by or by where the means of X, Y and Z are denoted by x̄, ȳ andz̄ respectively.Both approaches are, in general, different. But, in this paper it is shown that for most situations which may occur in the field of practical applications in agronomy and plant breeding both procedures will lead to nearly identical results. Only in some special situations the two results differ significantly. These conditions are investigated and explicitly given.Some explicit formulae (approximations) for the calculation of mean harvest indices are derived and discussed.Finally, all the theoretical investigations and results are demonstrated and applied to a numerical example of winter‐rapeseed

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1990.tb00838.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractDifferent potato cultivars were subjected to 10−6M kinetin treatment prior to the transplantation in saline soils (pre‐kinetin treatment) and to the plants already growing on the saline soils (post‐kinetin treatment). The kinetine when applied before the exposure of plants to saline soils showed promotory effects on growth, tuberization and some biochemical parameters of potato at 0.5 % salinity. The degree of inhibition in number of tubers and yield was reduced at 1 % salinity due to pre‐kinetin treatment. The level of proline, reducing sugars and sodium was increased in different plant parts to maintain the osmoregulation. However, kinetin did not play any specific role in reducing down the increase in proline content resulted due to salinity. The level of K+was found to be higher at low salinity in all the cultivars of potato. Higher concentrations of proteins and enhanced activity of starch synthetase at low level of salinity suggest the salutary effect of Na+in metabolic functions of plant cells. The nitrate reductase (NR) activity was appeared to be more sensitive than starch synthetase. This could possibly be due to the localization of the enzyme and the cellular concentration of toxic substances increased under stress. Total Glyoalkaloids (TGA) content was reduced at both the salinity levels irrespective of kinetin treatments. On the contrary Na+content was increased in all the treatments of kinetin at both levels of salinity. During this study cvs.Red Lasoda, PatronesandAtom alueapproved to be more tolerant as compare to rest of the cultivars tested. This could be a combined effect of genetic setup, amendments in saline soils and pre‐kinetin treatments of plants exposed to various regimes of salinity. Furthermore it is argued that salt tolerance limit can be extended upto certain level of salinity by pre‐kinetin treatment in po

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1990.tb00839.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractVariations of yield and quality characters of four spring oilseed rape cultivars (B. napusL.) arranged in 16 or 32 cm between drills and under three population densities (30, 60 and 90 plants/nr) were investigated in a split‐plot design with three replications in 1986 and 1987 in West Germany.CultivarCallypsogave the highest seed and oil yields per plot and the highest seed index, harvest index and seed yield/main stem, per branches and per plant. Differences due to arrangements were significant in 1986 only, i.e., the value of a special plant distribution was more pronounced under unsuitable weather condition (as in 1986). With respect to the three population densities, most of the characters showed significantly higher values with 30 plants/nr. Only seed yield and oil yield per plot that showed 7.27% and 5.6% increase, respectively, under the highest population density (90 plants/nr) but the differences were insignificant.The highest oil content was obtained from cultivarCallypsoand from the lowest population density. By contrast, higher protein content was obvious under higher population densities and the differences from the lowest density were significant in both years. Differences in fatty acid composition were not significant for the three main effect

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1990.tb00840.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractMorphological characters, dry matter production and the distribution of14C‐assimilates of the flag leaf were investigated on two spelt varieties (OstroandRouquin) and two wheat varieties (ArinaandProbus) under controlled conditions. Single plants were grown at three different temperature regimes (18/13 °C continuously = T1; 18/13 °C until anthesis and 13/8 °C after anthesis = T2; 13/8 °C until anthesis and 18/13 °C after anthesis = T3).Spelt produced up to 10 tillers more per plant than wheat. However, tiller reduction was also higher for spelt so that both species finally had a similar number of ears per plant.Under favourable conditions (T1) the large single grain weight of spelt, did not fully compensate for its lower kernel number. As a result, the grain yield per ear was 12 % higher in wheat than in spelt. Under low temperatures during grain filling (T2), wheat did not fill it's kernels completely; thus, under these conditions grain yield of spelt was 12 % higher. It seems that the kernel growth of spelt is less limited as compared to wheat (maximum single grain weight reported at T2:Ostro67 mg;Rouquin63 mg;Arina53 mg;Probus47 mg [SE 1.8]).The distribution of thel4C from the flag leaf was similar for both spelt and wheat. At anthesis the highest amount of14C was found in the last two internodes. Three weeks after anthesis, the ear of the main culm was the most important sink (exception T2). Between 48 h after the labelling with14CO2and maturity, different amounts of assimilates were translocated from the stem into the ear of the main shoot and partially also into the tillers.In conclusion significant differences were found between spelt and wheat in tiller formation, grain number per ear, single grain weight and grain yield. Especially under low temperature during grain filling kernel growth of spelt was less limited than that of

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1990.tb00841.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractGerechte designs are row and column designs which have an additional blocking structure formed by spatially compact regions. In this paper, and a companion paper (Baileyet al. 1990) we consider the correct analysis of these designs. In this paper we discuss the purpose of gerechte designs, and we note that the regions are not orthogonal to the rows and columns. This means that the usual sums of squares for rows, columns and regions are not additive. We show how the correct analysis can be performed, either through the use of appropriate formulae, or by the use of a statistical package. In the companion paper we show that the correct analysis cannot be justified by a randomization argument, and we outline other developments in analysis and design that may be more satisfactory.

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1990.tb00842.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractUnder controlled environmental conditions, the effect of optimal (20 °C) and supraoptimal (30 °C) root‐zone temperature on root activity (respiration, soluble sugar content, ethylene release, nitrogen uptake and translocation) was studied in water culture with two potato clones differing in the heat tolerance of their root systems. Root respiration was little affected by raising temperature from 20 °C to 30 °C. However, in both clones assimilate allocation to the roots was strongly depressed. In the heat sensitive clone LT‐1 exposed to 30 °C root‐zone temperature, concentrations of soluble sugars in the apical root zone (0–10 mm) increased with time, presumably as a result of the cessation of root growth. The rate of nitrate absorption was not significantly affected by root‐zone temperature. However, the export of nitrogen (xylem exudate) was depressed in the heat tolerant clone whereas in the heat sensitive clone the export of total nitrogen and the proportion of nitrate increased. No effect of root‐zone temperature on ethylene release was observed in

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1990.tb00843.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe inter‐relationships between fifteen quantitative characters of spring oilseed rape were computed using four “free erucic acid” cultivars viz.Callypso, Semit 2080, Semu DNK 203/84andSemu 304, grown under two different distances between drill rows (16 and 32 cm) and three population densities (30, 60 and 90 plants/m2). The experiments were carried out in Kiel, West Germany, in 1986 and 1987 seasons.Positive and highly significant values were obtained in the two seasons between seed yield per plant and the characters: dry matter (DM) per plant, per main stem and per branches, number of branches, siliqua per plant or per branches and yield per branches. All the characters that showed strong association with yield/plant behaved in a similar way and similar magnitudes with yield/branches. By contrast, yield/main stem showed different magnitudes in the two years with the previous characters and the association was weak or absent in most cases.Seed index and the quality traits (oil and protein %) did not correlate significantly with the majority of the characters studied. Only the association between DM/main stem and protein content showed highly significant negative values in both seasons.Path coefficient analysis revealed that number of siliqua per plant had the highest direct effect on seed yield/plant in both years. The source character (DM) affected yield/plant indirectly through number of siliqua per plant and the indirect contribution was high m both

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1990.tb00844.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractEffect of fungicides on fungus diseases and on the quality of the spring barley (Hordeum vulgareL.) in the subalpine area of SloveniaThe 1000 kernel weight of brewer's spring barley can be enlarged by using fungicides triadimephone or propiconazole. Propiconazole has better effects on the net blotch. The both fungicides reduce protein contents, however, these alterations hasn't great practical value. By using the above mentioned fungicides, the yield of spring barley was statistically remarkably higher that that of unsprayed control. The 3 years average yield of cv.Kragujsprayed with propiconazole was statistically remarkable higher than any other cultivar in any other experimented variant.

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1990.tb00845.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractOn the basis of a long‐term field experiment with a progessive monoculture of wheat carried out on the research station Hohenschulen (University of Kiel), the yield reaction of wheat in monoculture was analysed with help of a multiple regression approach.The mean yield of several years declines till the third resp. fourth crop, it increases later (‘decline‐effect’ in the larger sense) without reaching the initial level however.The weather considerably influence the absolute yield level as well as the yield trend in dependence upon the number of successive wheat crops. Interactions between yield and soil conditions are only slightly marked if the absolute yield is considered. The yield components, however, react differently according to the soil conditions.Crop management measures such as the choice of varieties and the application of BCM‐fungicides or N‐fertilization were only able to reduce yield losses, but not to p

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1990.tb00846.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY