摘要:

AbstractMaintaining crop residue on the soil surface is an important part of conservation tillage. Although broad effects of residues on soil temperature (Ts) are well documented, the methods to predict soil temperatures under various surface residues and tillage conditions are limited. Using the Tsat 0‐, 0.05‐, 0.10‐, and 0.30‐m depths, we developed a simplified model to predict Tsfor a uniform soil from air temperature (Ta) data. Data were collected under various tillage and surface residue conditions after wheat (Triticum aestivumL.) harvest. Residue management treatments were disk, sweep, and no‐tillage (with standing or shredded residues). The model predicts maximum and minimum Tsat 0‐, 0.05‐, 0.10‐, and 0.30‐m depths using maximum and minimum Tsmeasured at 2‐m above the soil surface, residue mass, apparent thermal diffusivity, and initial Ts profiles. Mean absolute deviation between simulated and measured maximum and minimum surface Tswere 0.53 and 0.44 °C or less, respectively. Root zone maximum and minimum T, were simulated within 0.14 to 0.91 and 0.27 to 0.95 °C, respectively, of the measured Ts. Greater precision of maximum and minimum soil temperature predictions with depth was obtained by using apparent thermal diffusivity calculated from initial Tsprofiles. The proposed model can be useful in predicting Tsprofiles required for

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1994.tb00153.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractPlant growth regulators (PGR) have potential to increase grain yield and may also alter grain protein levels of cereal crops. A 3‐yr field experiment with spring barley (Hordeum vulgareL.) and wheat (Triticum aestivumL.) cultivars was conducted to determine whether ethephon treatment increased protein concentration, protein yield, and grain yield. A greenhouse experiment was also conducted to evaluate the response of barley grain protein concentration to gradual addition of ethephon (2.2 × 10‐3mM) or chlormequat (5.8 × 10‐3mM) solution after an thesis. Under field conditions, ethephon treatment increased barley and wheat grain protein concentrations by as much as 16 % but decreased grain yield so that protein yield increases were small or did not occur. ForLaurierbarley, total gram N content was increased by up to 20 % in one year of this study. However, over the 3 years, an inverse relation existed between grain protein and yield. Greenhouse data showed that i) the gradient in grain size and protein concentration among spikelets of a spike, which is established before anthesis, was not affected by either chlormequat or ethephon; and ii) chlormequat increased grain protein by 7 to 11 % whereas ethephon increased protein concentration by up to 13 % in one of the two experiments. Our data indicate that PGR can alter protein accumulation in the grain, and thus, the quality of bread wheat and feed barley crops can be increased m regions with a short crop‐growing season. However, a portion of the increase in gram protein concentration is due to decreased starch deposition, which is associated with yield reductions. The greenhouse data confirmed that a portion of the increase in grain protein concentration due to PGR application is caused by increased protein accumulation in the bar

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1994.tb00154.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe time course of injuries and electrolyte leakage as well as changes in leaf water content and relative turgidity during chilling at 5°C, 65 or 100 % relative humidity (RH) were determined for seedlings of two maize hybrids differing in chilling tolerance.In the course of chilling of entire seedlings the statistically significant injuries and increased leakage of electrolytes occurred first, followed by significant water deficit in leaves which was independent of RH and genotype. However, during prolonged chilling high and significant correlation between the level of chilling‐induced water stress and the extent of injuries was observed. Thus it has been assumed that the main factor responsible for primary chilling injuries in maize seedlings is the immediate influence of chilling temperatures on the cell membranes, and not the secondary water stress. The level of the water stress and the extent of the dehydration injuries under chilling conditions depended on the chilling sensitivity of the genotype. Differences between the examined genotypes consisted not only in delayed chilling injuries in a chilling tolerant hybrid, but also in significantly lesser effects of these injures on water relations.However, exposure to low temperature of the aboveground part or of the roots of the seedlings only, caused first the chilling‐induced marked water deficit in the leaves and next increased leakage of electrolytes. A direct effect of chilling temperature on the membranes in a situation when only a part of the seedling is being chilled, may be less harmful to the plant as a whole owing to normal functioning of the non‐chille

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1994.tb00155.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractGerminating seeds and young plants of winter rape var.Górczañskiwere vernalized for 56–63 days under conditions of 9‐hour day, at the temperature 2 and 5 °C and in continuous darkness at the temperature 2 °C. After vernalization the plants grew under conditions enabling to complete vernalization: in a glass‐house at the temperature day/night 15/10 °C and in semi natural conditions of open vegetation hall in the period from June till August. After sub‐optimal vernalization further growth of the plants at lowered temperature increased its effectiveness (completion of vernalization). Depending on the degree of the vernalization of the plants the completion of their vernalization was both obligatory, i.e. conditioning the acquisition of the ability of generative development, and facultative i.e. accelerating this development. It has been demonstrated that the population of plants of the examined variety is strongly differentiated not only with respect of vernalization requirements in the particular plants, but also what regards the effectiveness of vernalization completion. New observations have been made indicating that the mechanisms controlling the successive phases of generative development, i.e. phase of forming flower buds and the flowering phase are not identical which may be interpreted as indicating that the “flowering factor”

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1994.tb00156.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractAbout one‐third of the total rice is grown under rainfed lowland conditions, mostly m south and south‐east Asia. Crop productivity in this ecosystem can be improved by adopting suitable management practices as drainage of excess water is not feasible in the catchment and coastal areas. Field experiments were conducted using a long‐duration (165 days), photosensitive, semi‐tall (150 cm) rice cultivarUtkalprabhaestablished through direct sowing or transplanting on different dates under 0–50 cm water depth at Cuttack, India, during 1989–91. Direct sowing was done in lines in dry soil from 10 May onward using 400 seeds/m2and continued at 10 day intervals until June. Transplanting was done after accumulation of water in the field from July until 15 August with seedlings raised in nursery seed‐beds with or without fertilizer application (100 kg N and 8.7 kg P and 16.7 kg K/ha) and tillers removed from the direct‐sown crop. Seedling emergence varied significantly from 127–212/m, irrespective of sowing date and was dependent on rains received after sowing. However, the early sown crops in spite of poor germination, performed well due to better establishment and tiller production before water rose to higher depths in the field. There was a decreasing trend in grain yield, particularly when the sowing was delayed beyond end of May. The loss in yield with delayed sowing in June was due to poor crop stand which could not be compensated for by applying 50 % more seed (600/m2) and N fertilizer (60 kg N/ha). Removal of some of the tillers (100–130/m2) from crops sown on 30 May with 600 seeds/m2for planting on an equivalent plot area did not cause any adverse effect on the performance of mother crop. The anticipated shortfall in yield due to lower panicles/m2with clonal tiller separation was compensated for by the resulting increase in panicle weight.The performance of transplanted crops depended greatly on the water depth at or soon after planting. In 1990, planting on 15 July in 30 cm water depth helped in relatively better establishment and grain yield at par with sowing on 10 May. However, in 1991, when there was a sudden and rapid increase in water level to higher depths (50 cm) immediately after planting, the early planted crops produced only a negligible yield (0–1.2 t/ha). Highest yield was obtained from the crop planted with clonal tillers followed by that raised with fertilized and unfertilized nursery seedlings. Clonal tillers were taller (90 cm) and had more dry weight (1.78 g) compared with nursery seedlings (50–80 cm and 0.25–0.91 g). Therefore, the clonally propagated crop established well and acclimatized faster in the similar flooded environment, resulting in significantly higher grain yield particularly under late planted conditions. The results suggested early sowing by the end of May and transplanting with clonal tillers uprooted from the direct‐sown crops for higher productivity of rice under uncontrol

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1994.tb00157.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe influence of undersown green manure crops for fallows – set‐aside land – in view of vegetation‐development and the dynamic of nitrateIn view of the establishment of rotational fallows ‐ set‐aside land ‐ as well as the bridging of the vegetation‐free winter period the suitability of different undersown grasses and legumes m winter cereals was investigated in field trials.Festuca rubradeveloped well in winter barley and winter wheat. The success of the cultivation ofLolium perenne, Trifolium pratenseandTrifolium repensin winter cereals is uncertain because of the risk of light and water deficiences.Dactylis glomeratacaused an negative influence on the yield of the cover crop. During the fallow period only low levels of nitrate could be found in the soil. Under fallow tilled repeatedly complete fallow‐ a nitrate accumulation could be observed during the fallow period. After ploughing up the fallow vegetation, nitrate concentrations ‐ depth 0–150 cm – increased to 60 kg NO3‐N · ha‐1after the natural fallow without seeding, between 60 and 130 kg NO3‐N · ha‐1afterTrifoliumand between 160 and 210 kg NO3‐N · ha‐1after complete fallow. Lowest nitrate levels were observed from the grass‐sites. UndersownFestuca rubraseems to be the best choice in order to compete with weeds, to form a dense sod and to prevent nitrate leaching. In general a se

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1994.tb00158.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractA study evaluated the response of two varieties of beans (Phaseolus vulgarisL.) to different soil moisture levels during a dry season. The soil moisture regimes maintained throughout the growth period were field capacity, 70–75 %, 50–55 % or 20–25 % available soil moisture.Plant growth, yield and nodulation were optimal when plants grew at high soil moisture levels. With increasing stress, all measured parameters of both varieties were reduced. However, polebeans, with its vine type of growth was affected to a greater degree than bushbeans. In contrast, nodulation and nodule activity of both variables was affected by moisture stress.A second experiment evaluated the effects of different soil moisture levels over the growth cycle of bushbeans, which produce greater yields under drier conditions. The highest yields were obtained at higher moisture levels throughout the growth cycle. Moisture stress up to flowering reduced yields to a greater extent than when the plants were subjected to reduced soil moisture after flowering appearance. Some casual mechanisms of the results of the experiments and possible implications for incorporating this popular vegetable legume in rainfed agricultural systems are pres

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1994.tb00159.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractA field experiment was conducted at the Central Potato Research Institute, Shimla, in 1991 to ascertain the effect of nitrogen fertilization on berry and true potato seed production in two commercial cultivars. It was observed that the 100 seed weight ofKufri JyotiandKufri Lalimawas significantly higher when higher doses of nitrogen (120 to 240 kg/ha) were applied. It was further found that 100 seed weight was not related to the berry size.

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1994.tb00160.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY