摘要:

AbstractA lysimeter trial is described in which the fate of15N was monitored in a sand, loam and clay soil by using it over a period of 6 years. The following results were obtained.1. The uptake of fertilizer nitrogen by plants, determined by using15N, is lower than by using the conventional method (“difference method”). Nitrate15N is better utilized by the plants than is ammonium15N. The total nitrogen uptake only gives hints of these differences.2. The extent to which plants utilize fertilizer15N is between 38 and 58%; in the case of the method of differences this figure is between 48 and 68%.3. Plants remove more nitrogen from the soil when fertilizer N is applied than when without fertilization. The influence of these two nutrient forms is of subordinate significance.4. After a trial period of six years between 26 and 54 % of the fertilizer15N remains in the soil. The resulting sequences are clay>loam>sand>and ammonium>nitrate.5. The immobilization of the fertilizer15N is most pronounced in the first four years but then decreased considerably; in the case of the sandy soil it is then even slightly regressive.6. The biggest part of the15N is deposited in the uppermost layer of the soil. The amount of15N in the deeper layers is diminished appreciably. The type of soil has a greater influence than the form of nitrogen.7. If the amount of fertilizer N left in the soil is compared with the N losses from the soil's reservoir (plants' uptake, leaching) there is a negative balance for the soil nitrogen which mainly is determined by the type of s

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1990.tb00810.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractFive sunflower hybrids and one open‐pollinated variety were sown at two locations in West Germany and at two‐sowings at Giza, Egypt (summer and winter seasons). Cultivars showed different response concerning oil and protein contents as well as fatty acid composition. Highest protein content was observed from Giza in winter season. Cultivars differed significantly with this respect under different environments. However, oil content was not significantly affected by environments X cultivars interaction.Regarding fatty acid composition, palmitic and stearic acids were insignificantly affected. However, highest oleic acid percentage (57.5%) was observed at Giza in summer sowing byNhy, hybrid, while at Giza in winter sowing the highest value (25.7%) was produced bySemu 209hybrid. The differences between the two Germany locations were relatively low in range from 14.6–17.6%. Concerning linoleic acid, it showed an opposite trend.Environments X cultivars interaction showed significant influence on total tocopherol co

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1990.tb00811.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe effect of plant water stress on net photosynthesis, leaf growth, yield and yield‐related components were investigated in a single experiment in order to determine in which way water deficits affect sunflower yields.Sunflower plants, grown under controlled temperature regimes, were stressed during budding, anthesis and seed filling by withholding water until the leaf water potential reached ‐1600 and ‐2000 kPa. Leaf area of unstressed plants significantly exceeded that of plants under severe stress during all growth stages investigated. The CO2uptake rate per unit leaf area as well as the total uptake rate per plant, significantly diminished with stress, while this effect drastically increased during the reproductive phase of the plant. Although this resulted in significantly smaller heads and kernels, it did not affect the number of seeds borne in the inflorescence. Severe stress during anthesis and seed filling resulted in more empty kernels. Moderate and severe stress during budding significantly lowered both grain and oil yields while plants that experienced moderate stress during anthesis and seed filling significantly outyielded those under severe s

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1990.tb00812.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractAn experiment was conducted at Lexington, K.Y., USA (38° N latitude) utilizing 18 soybean (Glycine max[L.] Merr.) genotypes in three stem termination groups (determinate, indeterminate, and segregating) to compare eight methods of estimating seed filling period in terms of 1) ability to differentiate among genotypes, 2) lack of bias towards any stem termination type, 3) ease of measurement, and 4) consistency across environments. Growth stage estimates R1 to R8, R4 to R7, R5 to R7 and the reproductive period duration (estimate of the time period of the linear increase in harvest index) detected significant differences among the seed tilling periods of the genotypes. Significant stem termination group measurement method interactions were present, but because the indeterminate stem termination group had a shorter seed filling period than the other two groups for most methods, we were unable to evaluate bias towards stem termination type. The growth stage methods required 4x to 10x less time for data collection than the effective tilling period and reproductive period duration methods. Only the R4 to R7 and R5 to R7 growth stage estimates had significant rank correlation coefficients among genotypes across years. From this and previously published evidence we recommend using the R5 to R7 estimate of seed filling period following the separation of genotypes into stem termination classes for the selection of soybean genotypes based on seed filling period duration

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1990.tb00813.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractEighteen soybean (Glycine max[L.] Merr) cultivars from maturity groups V and VI were screened with twoBradyrhizobium japonicumstrains (USDA 110 and TAL 378) in the greenhouse to determine N2fixation (C2H2:reduction) rates. Antibiotic resistant markers were used for observing nodule occupancy. CultivarsL.‐76‐0132, PI 159319, Hoberland, Lee, PI 22173andCentennialshowed high nitrogenase activity of 6.25, 5.54, 17.43, 4.73, 6.94, and 4.81 μM C2H4/Pl/hr, respectively. CultivarsPI417419, PI 230978, Ogden, andFC 31665showed low nitrogenase activity of 1.51, 0.80, 0.62 and 0.94 μM C2H4/Pl/hr, respectively. The data from this screening experiment suggest that the N2fixation varied among genotypes and all the nodules were occupied by the inoculated strains only. Rhizobial strain effect was observed among soybean cultivars (

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1990.tb00814.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractSoil burning (“guie”) is a traditional farming practice in restricted areas of the Ethiopian highlands. Sods with adherent soil of grazed fallows are burnt which leads to comparatively high yields of the subsequent barley (Hordeum vulgareL.) crop. The weed species coverage and steadiness on burnt and unburnt spots of guie fields have been surveyed within the 1984/85 and 1985/86 growing periods using the Braun‐Blanquet cover‐abundance scale. On burnt spots weeds developed just about 1/3 of the cover on unburnt ones with a comparatively low share of monocotyledonous species. The total number of species collected was 103 (of 33 families) on unburnt spots and 77 on burnt ones. The average number of species/site was 39 and 26 respectively. The Poaceae, Asteraceae, Fabaceae and Caryophyllaceae were the most diverse families recorded with 27, 12, 10 and 6 species respectively. Species of highest steadiness likeRanunculus multifidusForsk.,Polygonum nepalenseMeissn.,Guizotia scabra(Vis.) Chiov. andDicbondra repensJ. R.&G. Forst. were significantly reduced in cover due to

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1990.tb00815.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractTriticale (X Triticosecale Wittmack) cultivarsCouncilandMorrisonwere planted in mid‐September (early planting) and mid‐October (late planting) in 1984 at the Alabama A&: M University‐experiment station for studying organic matter digestibility. The plants were harvested at the tillering, milk and dough stages and samples were subjected to proximate analyses and in vitro digestibility tests. A 1,100 lb Hereford steer fitted with a permanent ruminal fistula was used as the rumen fluid donor. In vitro dry matter digestibility (IVDMD) and in vitro organic matter digestibility (IVOMD) were determined by Moore's modification of the two‐stage digestion technique of Tillyand Terry(1963). Triticale cultivarCouncilwas comparable toMorrisonfor phosphorus (P), dry matter (DM), ceil wall content, IVDMD and IVOMD. Crude protein (CP) and ash content were significantly higher forMorrisonthan forCouncil, while gross energy (GE) was significantly higher forCouncilthan forMorrison.Both early and late plantings showed similar levels of DM, GE, P and cell wall constituents. However, CP and ash content were higher for early planting than late planting. The tillering stage was consistently higher than the milk or dough stages for CP, ash, P, calcium (Ca), IVDMD and IVOMD. The results indicate that the milk stage was superior to the tillering or dough stages in DM and cell wall content. Results from this study showed no significant differences in digestibilities for two triticale cultivars and planting dates. Based on the higher DM content at the milk stage, it seems that milk stage in triticale would be more acceptable as a forage than the tillering or doug

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1990.tb00816.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 biological yield Y: Z = X/Y. For many purposes the variance of Z is of major interest. In this paper several approximations for this variance are derived and their accuracy was investigated. These explicit formulae depend on some characteristics (means, variances or coefficients of variation, covariances or correlations) of the component variables grain yield X and biological yield Y. It is shown that for most practical applications the approximation v2z = v2x + v2y ‐ 2rvxvyprovides a sufficient accuracy for numerical calculations (vxvyand vzare the coefficients of variation for grain yield X, biological yield Y and harvest index Z and r denotes the correlation coefficient between X and Y). Some conclusions on the relations between vx, vyand vzare derived.Finally, all the theoretical investigations and results are demonstrated and applied to a numerical example of winter‐rapeseed d

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1990.tb00817.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractSoybean is little grown in the semi‐arid zone of the northern fringes of the Sudan savannah belt of Nigeria despite a seemingly good potential for the early maturing varieties. To explore the potential of the crop in this region a determinate soybean line was sown at 2 sites in 1986 at four planting densities of 7.5, 10.0, 12.5 and 15.0 plants/m2in three row spacings of 40, 60 and 75 cm. Both the above‐ground biological and grain yields increased with planting density. Row spacing had significant effect on yield only at the early planted Site 1, where 40 cm row spacing outyielded other rows. The increase in yield at high densities and narrow row was mainly due to increased pod and grain numbers/m2Onset of competition began to manifest as from flowering and intensified thereafter. However, the post anthesis competition did not affect grain filling and so mean grain weight and harvest index were similar in all treatments. Late planting at Site 2 reduced yield by between 20 and 30 % particularly at high densities and in narrow rows. The results indicate a fairly good potential for soybean in this region, and yield advantage due to moderately high planting densities and narrow spac

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1990.tb00818.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY