Winter Depth Research Articles

An integrated model-approach to the effect of water management on crop yield

Quantifying the effect of drainage on crop yield is of essential importance in agricultural management. In this article a model is described with which this effect can be computed. For both arable land and grassland the factors acting in spring, summer and autumn are dealt with separately.Arable land. In spring sowing date is the main factor affecting the crop yield. Sowing date depends on the tillage conditions of the soil toplayer. By means of an existing model, the course in time of the soil water tension of the upper layer is simulated in connection with rainfall, evaporation, drain depth and drain intensity data. Using specific criteria on minimum soil water tension for tillage operations, the dates and number of workable days can be established from the model output. The expected yield depression is then derived, using an experimental relationship between yield depression and number of days of sowing delay.During the growing season the yield directly depends on the magnitude of the actual evapotranspiration. This value can be computed by means of a known evapotranspiration model for various drought frequencies, groundwater table depths in spring, drain intensities and amounts of water supplied. The yield can be obtained from the relationship between yield and relative evapotranspiration. Combining this yield with the yield depression obtained by means of the workability model gives the actual yield.In autumn crop yield is influenced by the working conditions during harvest. Via the workability model, the dates and the number of days available for harvesting are determined. Yields are derived from an experimental relationship between yield depression and number of days of earlier harvesting. An example is given for summer cereals growing on a heavy sandy loam soil under meteorological conditions prevailing in The Netherlands.Grassland. The effect of shallow groundwater table depths in winter and spring on the yield of the first and second cut can be determined with the workability model in an identical manner to that given for arable land. Because of lack of data, a slightly different approach was followed in this paper. With the workability model the course of groundwater table depth during winter and spring can be simulated and the mean depth determined. From the relation between yield depression and mean groundwater table depth over the period November through May the yield depression can be found. Combining this with the yield obtained with the evapotranspiration model gives the actual yield. An example representative for The Netherlands is given for grass on peat soil.

Studies on Matter Production in Wheat Plant : I. Diurnal changes in carbon dioxide exchange of wheat plant under field conditions

Diurnal changes in CO2 exchange of wheat plant and the relationships of these diurnal changes to environmental factors were investigated under field conditions. CO2 exchange was measured by using an assimilation chamber and at the same time, the principal environmental factors, such as intensity of solar radiation, air temperature, soil temperature, air humidity, CO2 concentration of air, etc. were also measured simultaneously. These measurements were carried out at intervals of 2 weeks from the early stage of growth to the full maturation. The results obtained are summarized as follows: 1. The photosynthetic rate during the daytime varied generally corresponding to the solar radiation intensity. 2. Basing upon the relationship of photosynthetic rate to solar radiation intensity, the modes of diurnal changes in photosynthesis were classified into the following three types. Type A: Under this type, the photosynthetic rate in the morning is equivalent to that in the afternoon, provided that the solar radiation is much the same in intensity. Type B: Under this type, the photosynthetic rate in the morning is lower than that in the afternoon even if compared with each other under the condition with the same intensity of solar radiation. Type C: Under this type, the photosynthetic rate in the morning is higher than that in the afternoon, even if compared with each other under the condition with the same intensity of solar radiation. 3. In the depth of winter when it was critically cold in the night, the diurnal change of type B was observed. However, in case of warm night the diurnal change of type A was observed. These facts suggest that, on ordinary days in the depth of winter, the photosynthetic mechanism of wheat plant is inhibited by the intense cold during the night, while it is relieved from the inhibition due to the warmth in the daytime. 4. From the beginning of April onward, the diurnal change of type C was observed predominantly, though the diurnal change of type A was observed as well on such days when the solar radiation was not so intense. 5. In the transitional period from autumn to winter, the types of diurnal changes in photosynthesis were irregular. Immediately after the invasion of the first severe cold little or no CO2 absorption was observed during daytime in spite of fine weather with bright sunshine. 6. The dark respiration of wheat plant changed corresponding to the air temperature during the night irrespective of seasons or of weather conditions.

Study on Aerosol Optical Depth in Winter and Summer Season in Bhaktapur

Aerosol optical depth in winter and summer season, 2009 was studied in Bhaktapur (Kausaltar). Spectral aerosol optical depth (AOD) measurements were estimated from a Microtops II Sun Photometer. The results indicated high values in summer and low values in winter. It also showed that AOD is larger in shorter wavelength and gradually decreases towards longer wavelength. The increasing value of AOD in summer season may be due to the accumulation of high speed dust particles. The lower values in winter months are due to the reduction of bigger particles. The spectral dependence of AOD on January 27 was found to be 0.64, 0.52, 0.48 and 0.35. The AOD at 340 nm in January and July were 0.63 and 0.62, respectively. The maximum and minimum value of AOD at 340 nm in the month of April and August were recorded as 1.62 and 0.56, respectively.Keywords: Sun photometer; Aerosol; Aerosol optical depth; Angstrom parameters; IrradianceDOI: http://dx.doi.org/10.3126/jie.v8i1-2.5122Journal of the Institute of Engineering Vol. 8, No. 1&2, 2010/2011Page: 269-276Uploaded Date: 20 July, 2011

Effects of treading perennial ryegrass (Lolium perenneL.) and White Clover (Trifolium repensL.) Pastures in winter and summer at two soil moisture levels

Abstract Two uniform perennial ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.) pastures, growing in a silt loam, were used (winter 1957 or summer 1958) to investigate the effects of periodical treading, where the soil was at 2 different soil moisture levels. Spray irrigation and mature Romney sheep were used. All treadings, especially where the soil was wet, reduced measured herbage yields. Total yields of dry herbage in lb per acre during winter 1957 included: not trodden—1,980; moist soil, 18 sheep treatment—1,670; wet soil, 18 sheep—270; S.E. ± 62; and others during summer 1958 included: not trodden—2,280; moist soil, 18 sheep—1,080; wet soil, 18 sheep—230; S.E. ± 74. Perennial ryegrass was consistent in being relatively tolerant of treading, while white clover was tolerant in the summer. Thus the proportion of perennial ryegrass increased in the trodden pastures, while Poa annua L. volunteered in bare spaces. Reduced yields appeared, in the main, to be due to the lower vigour of a lesser number of grass tillers in trodden pastures. Particularly in wet soil, direct effects on plants, such as root damage, plant displacement, and burial in mud, appeared to be important. There also appeared to be significant changes in the soil itself, such as limitation of soil air, indicated by gleying at 1–1 ½ in. depth in winter.

THE GROWTH CYCLE OF THE BLUEBERRY AND SOME FACTORS OF THE ENVIRONMENT

The effects of latitude, burning, and pruning on the growth cycle of the blueberry were studied and found to be as follows. The morphology of the growth cycle and the sequence of morphological changes were not altered by any of the factors considered. For spring and summer, a north and south difference of one hundred and fifty miles had no greater effect than that which is regarded as "seasonal". Burning and pruning delayed the spring and summer growth by about two weeks. For the late autumn and early winter, there was some evidence that morphological changes occurred in the distal florets during that period, but for the "depth of winter", that is from mid-December till the end of February, the winter bud was a morphological complex that, with the exception of the apical floret, always had the same structure regardless of latitude, burning, or pruning and this structure was the same as that found in normal plants during that season.

Country Rambles: a Field Naturalist's and Country Lover's Note Book for a Year

MR. WESTELL has made a serious mistake; he has let himself become the slave of his note-book. He seems to have made up his mind to write a year's diary for publication, with the result that he has filled it with trivialities which after a few pages will weary the reader, be he naturalist or not. On almost every page we find entries such as the following, which are taken quite at random:—“February 2. The snow will act as a deterrent on the singing of our feathered musicians, although I have often heard Robin and Wren singing in the very depth of winter, evidently cheered by the transient gleam.” “arch 21. I was tempted out into the garden early by the brilliant sunshine, and did a bit of gardening. Chaffinch ‘pinking.’ How delicate-looking the first Snowdrop as. it peeps through the brown earth!” “June 10 (among other similar entries). What a variety of small beetles cross the path of the rambler, like dark little jewels darting about in the sunlight! There are many hairy caterpillars too. Cannot they move at a rate ! How they curl up into the ball of protection!” No wonder that we read on the same page, “How often the Note-book comes out at this season! ”Mr. Westell's mind has been working more upon his note-book than upon nature, and he would do well to leave it behind him for some time to come, and to reconstruct his ideas of observation and of a naturalist's work. When he touches a difficult or doubtful problem, he shows us at once what manner of naturalist he is. On p. 125 we read that “an instance is recorded by Herr Muller (sic), a well-known German Naturalist, of a Cuckoo sitting on, and hatching, her own fledgling. Three Cuckoo's eggs were found by Herr Muller in a hollow under a tussock of grass, &c.“This statement seems to be taken from Dr. Japp's book on the Cuckoo; the Herr Muller is Adolf Müller, the forester; the occurrence he described, though, of course, in itself not impossible, has not been accepted by ornithologists whose opinions at any rate deserve some consideration, e.g. Prof. Newton, Mr. A. H. Evans, and Mr. Howard Saunders. Yet Mr. Westell retails this as a proved but extraordinary fact, without making the least attempt either to test the truth of it himself by going to the original source, or to collect the opinions of scientific naturalists on an alleged zoological fact of such great importance. He has to learn that there are other qualifications for a naturalist besides the constant companionship of a note-book and a binocular glass. We are very far from wishing to discourage the proper use of these, or the intelligent enjoyment and observation of nature, but what we cannot possibly encourage is the publication of bulky and expensive volumes like this (weighted, too, by photographs, only some of which are really excellent), which cannot satisfy the real naturalist or even the ordinary reader; and in this we are sorry to disagree with Mr. F. G. Aflalo, who has written a kindly preface to the book. It is to be hoped that Mr. Westell's love of the country and of nature will in the course of time be turned to better account.

Birds

I propose on the present occasion to give a complete account of the Avifauna of Kerguelen Island, founded on the collections in the British Museum (partly made bv the Rev. Mr. Eaton, partly by the naturalists of the Antarctic expedition) and on the reports of the German and American expeditions, which have been recently published.* The American expedition obtained twenty-one species, the German naturalists recording twenty-three.† With regard to the Antarctic Expedition, Sir Wyville Thomson thus writes:— “ This expedition had the extraordinary advantage of having Dr. Hooker attached “ to it as one of the assistant-surgeons, and the surgeons to the Erebus and “ Terror , Dr. M‘Cormick and Mr. Robertson, and the assistant-surgeon of the “ Terror , Dr. Lyall, were all zealous naturalists, and co-operated heartily with “ Dr. Hooker in his work, so that every possible advantage was taken of the “ sixty-eight days of their stay in Christmas Harbour. Their visit was, however, “ in the depth of winter, and although the actual difference between the winter “ and summer temperature is not so great as might have been anticipated, the “ winter weather is so boisterous and unsettled, that on forty-five of the sixty-eiglit “ days it blew a gale, and on three days only neither snow nor rain fell.” Under these circumstances, therefore, it is not a little creditable to the officers of this expedition that they managed to collect a series of nearly every species obtained by the more recent visitors to the island, while they procured several species which none of the latter have met with.

Fertilisation of the Hazel

IN NATURE for April 7, 1870 (vol. i. p. 583), Mr. Marcus Hartog stated, as the result of his observations, that the male catkins and female flowers of the hazel are not simultaneously developed on the same twig, and that therefore a kind of quasi-cross-fertilisation necessarily takes place. Although convinced at the time that my observation did not tally with Mr. Hartog's, it was then too late in the season to submit my impression to a practical test. During the past week I have closely observed the hazel bushes in flower, and have found on every bush which has come under my notice, the female and male flowers in a perfect state of development on the same ultimate twigs, in close proximity to one another, the stigmas being frequently loaded with pollen-grains, apparently from the neighbouring catkin; at all events there appears no provision of nature specially to promote fertilisation from other bushes. We see in fact here a confirmation of the general law suggested in my paper in the first number of NATURE, on “The Fertilisation of Winter Flowering Plants,” that when plants flower in the depth of winter, and at a time when no or few insects are about, self-fertilisation is the rule rather than the exception, or in the case of unisexual flowers, as near an approach to self-fertilisation as is possible under the circumstances.