Acre Plots Research Articles

Behaviour of bees visiting male-sterile field beans (Vicia faba)

1. A colony of honey-bees was put beside a 1/36 acre plot of male-sterile and male-fertile spring beans in 1965, but very little bean pollen was collected and no honey-bees were seen pollinating either male-fertile or male-sterile flowers.

Integration of the heliothis nuclear polyhedrosis virus into a biological control program on cotton.

A biological control program for Heliothis species on cotton consisting of the naturally occurring predator-parasite complex and the nuclear polyhedrosis virus was integrated into a cotton-insect-biological-control program. Heliothis control with biological agents was compared with a toxaphene-DDT-methyl parathion control program using 25–30 acre plots. The virus was applied at 1.2×1011(20 I.U), 30×1011(50 I.U), and 6.0×1011(100 I.U) polyhedral inclusion bodics (PIBs) per acre. The initiation of virus applications was varied to evaluate the effectiveness of the virus against various ages of larvae, The Heliothis biological control program compared favorably with the insecticide program when virus application was initiated to coincide with hatch of high egg populations.

Estimation of Dry Weight of Tree Components and Total Standing Crop in Conifer Stands

The distribution of dry weight among six tree components is shown for balsam fir from 1 to 10 inches in diameter at breast height. Component dry weight and total standing crop are estimated and compared for a 0.2—acre plot using methods based on every—tree summation, stand tables, and several short—cut techniques based on “average” trees. It is concluded that the average tree approach is useful only where a rough estimate of total biomass is desired.

Quantity, Distribution, and Variability of Organic Matter and Nutrients in a Forest Podzol in New York

AbstractThe organic matter under yellow birch‐red spruce forest (Betula alleghaniensis Britton‐Picea rubens Sarg.) growing on well‐drained, outwash sands of the Adams series was sampled intensively on eight one‐tenth acre plots in the Adirondack Mountains of New York. Under old, undisturbed stands the mean depth of the forest floor was 6.4 inches (16 cm) and the mean weight was 216,300 ± 8,800 (90% confidence interval) lb/acre (242 metric tons/hectare). There was approximately 175,000 lb/acre of organic matter in the forest floor and about 142,000 lb/acre in the upper three horizons of the mineral soil. The average bulk density of the forest floor was 0.14 g/cm3. A theoretical O horizon accumulation curve was drawn based on samples from plots having different ages of accumulation. These ages were inferred from ecological information and from evidence of fire history. The concentration of organic matter in the B2h horizon was positively correlated with age of the forest floor. The undisturbed forest floor contained approximately 2,850 lb/acre of nitrogen or about 43% of the estimated total in the nutrient cycle. It also contained approximately 150, 90, and 620 lb/acre of phosphorus, potassium, and calcium, respectively.Coefficients of variation ranged from .33 to .67, determined on the basis of 96 sample weights from the forest floor of each plot. Approximately 50 samples were needed to reduce the standard errors to 10% of the mean weights. Similar variability was found in the thickness of mineral soil horizons. Horizon thicknesses measured from a single soil pit in a 0.1‐acre plot were not reliable estimates of thicknesses when compared with those determined by taking 12 to 24 core samples spaced throughout the same plot.

WILD WHITE CLOVER SEED PRODUCTION

Field experiments on the management of ryegrass/white‐clover pastures for seed production were carried out from 1958 to 1961. Replicated trials with 1/6‐acre plots compared continuous grazing, rotational grazing and cutting once at the silage stage of growth as methods of pasture management from April to June. An additional mechanical method, gang mowing, was introduced in 1960 and Hayter mowing was used in 1961. In 1958 to 1960 the treatments were studied with and without the application of 70 lb nitrogen per acre. Clover flower heads per square foot, clover seed and ryegrass seed yields were greatest under continuous grazing, although in some years comparable results were obtained from the mechanical defoliation treatments. There were substantial differences between potential and harvested clover seed yields, the latter ranging from 20% to 75% of the potential yield. The weight of ryegrass seed harvested was highest under continuous grazing and least under the cutting treatments. The nitrogenous fertilizer increased the production of herbage dry matter and of ryegrass seed, but greatly reduced clover seed yields. The results are discussed in relation to the influence of weather on the incidence of flowering and the influence of methods of defoliation on flower‐bud emergence. It is concluded that mechanical methods of defoliation can produce yields similar to those obtained under continuous grazing, provided that cutting is carried out at the correct stage of growth.

Laboratory and Field Tests of New Insecticides for Grasshopper Control

New insecticides were evaluated for grasshopper control on rangeland in Western United States. The most effective of laboratory-screened compounds were field tested on 1½-acre plots with ground equipment or on 40- or 640-acre plots with aircraft. The most promising compounds from the field tests were Bayer 25141 ( O, O -diethyl O -( p -methylsulfinyl)phenyl phosphorothioate), Bayer 29493 ( O, O -dimethyl O -(4-methylthio- m -tolyl) phosphorothioate), Diazinon®) ( O, O -diethyl O -(2-isopropyl-4-methyl-6-pyrimidinyl) phosphorothioate), Dihrom® (1, 2-dibromo-2,2-dichloroethyl dimethyl phosphate), dimethoate, General Chemicals 3707 (1,3-bis(methoxycarhonyl)-1-propen-2-yl dimethyl phosphate), malathion, Monsanto CP-7769 (hexaethyl (ethylthiomethylidyne ) triphosphonate), posphamidon, and Sevin®(1-naphthyl methylcarbamate). A discussion of the techniques of evaluating new insecticides through testing in the laboratory and in small- and large-scale plots is presented.

The Effect of Certain Site and Soil Factors on the Establishment of Douglas‐Fir on the Tillamook Burn

AbstractThis paper presents a preliminary report of studies dealing with soil moisture‐seedling survival relationships conducted on the Tillamook Burn in northwestern Oregon during 1953. Ten one‐fifth acre plots were selected from the current years planting program. Survival was calculated on the basis of total trees planted.Factors investigated include: Percent slope, aspect, soil texture, structure, depth, organic matter content, and range of available moisture. Weather data were obtained from nearby lookouts. Soil moisture determinations were made weekly throughout the summer period.Although there were not sufficient plots to establish statistical significance, certain factors were found to be affecting survival. Among these were aspect, percent slope, and soil texture. Southerly aspects coupled with coarse textured soils and slopes greater than 40% showed the highest mortality. On the other hand, northerly aspects, loam and silt loam textures and slopes less than 40% had excellent survival. Between these two extremes various gradations existed. In all cases where high mortality occurred, soils had been depleted of available moisture (below 15 atm.) for periods approaching 30 days.

Soil Properties Related to Forest Cover Type and Productivity on the Lee Forest, Snohomish County, Washington

AbstractFive one‐tenth acre plots were established on Lee Forest to investigate forest site and type and soil relationships. One plot was in each of the following types and sites: western hemlock‐Douglas fir, site class III; Douglas fir, site class II; Douglas fir, site class III; western red cedar, site class III; red alder, site class I.Soils were sampled on these plots and the following data taken: effective depth, bulk density, texture, moisture equivalent, reaction, total nitrogen, and cation exchange capacity. In addition, weight and nitrogen content of the forest floor were determined and soil moisture followed throughout the 1953 growing season.Depth to a hardpan layer was an important criterion for productivity rating. High bulk densities impeded root growth and determined effective soil depth. The critical density differed for the different tree species. Total soil nitrogen and total cation exchange capacity were much greater in the more productive forest soils. The western red cedar and the red alder plots had shallow soils with excess soil moisture during a considerable portion of the year. Low soil moisture did not appear to be a factor in tree growth on any of the plots in the 1953 growing season although the soil on the red alder plot did become quite dry in late August and early September. The dominating influence in determining forest type seemed to be poor soil drainage.

Mound Changes after Ten Years in Colonies of Formica Exsectoides Forel

In May 1936 a population survey of the mounds of Formica exsectoides was made in a ten acre plot near Beltsville, Maryland. The position of each mound was plotted on a chart and the height measured. Ten years later this chart was used in making a resurvey. The area then showed few changes in plant development other than normal growth. A few Virginia pines had been cut along one side adjoining an area that had been cleared and cultivated sporadically before 1936.

Relation of Soils and Forest Growth in the Driftless Area of Southwestern Wisconsin

I he distribution of native vegetation and the rate of forest growth in relation to soils were studied on two transects. One of the transects extended for about 4 miles in Iowa and Sauk Counties; it crossed the Wisconsin River in a southnorth direction near Arena. The other transect extended for 2 miles in Richland County; it crossed the Pine River in a west-east direction near Hub City. In each floristic type, encountered on the transects, the soil was excavated to a depth of 6 feet, unless rock substratum or the ground water table was found at a shallower depth. The properties of soil profiles were studied in the field and in the laboratory. The composition of vegetation was recorded as to relative abundance and conspicuousness of different species. In forest types, the height, diameter, and age of trees were determined on one-fifth acre plots. The yields per acre were established on the basis of estimated stand density, height of dominant trees, and available yield tables (Gevorkiantz and Scholz, '47). The record of the ground cover plants was supplemented by a number of quadrat studies, confined to the major soil-forest units. The primary purpose of the transect study was to establish a natural basis for forest and farm woodlot management. Geologically the region studied is typical of the unglaciated area of southwestern Wisconsin. It presents sharply dissected cuestas with steep narrow ridges

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Resumen en español.

On the behaviour in the field of small grain obtained by premature harvesting

1. By premature harvesting, as early as 5 days after fertilization, dwarf grains are obtained which will germinate readily and produce normal plants, even though grain size may be only 10% that of fully developed grain. Such plants tend to attain the same final size as those from mature grain. This paper deals with the growth under field conditions of dwarf grain with regard to survival during the winter, and final yield.2. Pot cultures with vernalized winter and spring varieties of rye, wheat, and barley have shown that the high growth rate characteristic of dwarf grain is not confined to the vegetative phase of growth, but is also manifested after the ear has developed. The fact emerges that dwarf grain can be successfully vernalized.3. A field trial is described using three size classes of grain (mature, medium, dwarf) with mean grain weights of 33·93, 23·56 and 10·23 mg. respectively. These were sown (i) at sowing rates of 2 and 3 bushels per acre, and (ii) at uniform spacings of approximately 200 and 300 grains per 9 ft. row. A subsidiary experiment with spacing of 1 ft. was also carried out.4. All classes of grain germinated well and survival during the winter was uniformly high in the equally spaced plots; with the close spacing of the dwarf grain at 2 and 3 bushels per acre (plots 11 and 12) percentage survival was somewhat reduced.5. The effect of grain size and spacing on time of flowering was negligible.

A Three-Year Trial with a Feed Patch for Songbirds

In 1938 a trial feed patch for songbirds was prepared at Pleasant Valley Bird and Wildflower Sanctuary in Lenox, Massachusetts, by tilling a 1l acre plot of old field and sowing it with a mixture of selected seeds. Partially successful in 1938, the experiment was repeated-with minor modifications and improved results-by reseeding the same area in 1939 and 1940. The venture had two motives: (1) To improve feeding conditions for the summer resident and migrant fringillids already common on the Sanctuary, and (2) to attract a number of seed-eating birds which, for reasons not altogether clear, have always been absent or scarce. The feed patch functioned admirably in meeting the first need, but failed in the second.

Population studies with wheat: I. Sampling

The design and field technique of two large scale experiments, laid down to investigate the problems of sampling and “propinquity”, are described in detail. These experiments were designed so that the plant number, stem number, ear number, straw weight and grain weight for 7200 lengths of 6 in. of drill row, together with the position of each observation, might be obtained.The lowest sampling error, expressed as a percentage of the mean, is obtained by using the smallest sampling unit, but the large number of sampling units of this size that would have to be taken make it impracticable. The optimum sampling unit consists of 6 ft. of drill row, taken as 3 ft. of two adjacent rows. The size of the sampling unit is of greater importance than the shape in determining its accuracy, and little s lost by using sampling units of 18 in. of five adjacent rows.The nature of the observation affects the degree of sampling. In the experiments examined the plant number, stem number and ear number require very similar sampling, but grain weight requires a sample which is about twice as large as that required by the other observations.The percentage of the plot that must be taken as a sample (the sampling percentage) to obtain any given accuracy is related to the size of plot: the larger the plot, the lower the sampling percentage necessary. To obtain an error of 5% of the mean the sampling percentage for grain weight is approximately 5% in 1/20 acre plots, 15% in 1/100 acre plots and 43% in 1/600 acre plots if the plots are not subdivided. These percentages are similar to those calculated from various randomized block experiments in Cambridge.

Catastrophes and Pure Stands of Southern Shortleaf Pine

In the spring and summer of 1934 age determinations were made of a considerable number of southern short leaf pine trees, Pious echinata Miller, in Howard County, southwestern Arkansas. In the stony foothills of the Ouachita Mountains three areas of locally-designated virgin pine were studied and in each there existed a certain uniformity of age of trees that contrasted with true virgin stands, in which a wide and even distribution of age classes is usually found. The following is a table showing the age distribution of all trees on designated numbers of one-fourth acre plots. Table I shows that 68.57 per cent of the stand in area A became established in the nine year period between 1858 and 1867; similarly in area B, 63.16 per cent of the stand in the ten year period between 1812 and 1822, and in area C 85 per cent in the fifteen years from 1772 to 1787. The percentage of stand which came in before these periods is area AX 8.57; area B, 8.27; and area C, 5.0. Trees coming in after the periods made up the following percentage area A, 22.86; area B, 28.57; and area C, 10.0. In all three instances the closing of the period of intensive reoccupation was not as sharply marked as the beginning. It is known among southern foresters and lumbermen that purity of composition and uniformity of age in pine forests are the usual indicators of an old field stand, or the consequence of some catastrophe that wholly annihilated the previous plant cover. This is to say, a denuded area which is edaphically favorable, and which has seed-trees near, is soon seeded to pine and within the span of a few years a plant cover develops which for the most part resists further invasion of both hardwoods and members of its own species. From the foregoing data the natural inference is that some catastrophe destroyed practically all the forest in areas designated A, B, and C near the years 1857, 1811, and 1770 respectively. As enumerated above, certain seedlings and some older trees escaped. There followed a certain period in which the areas were intensively reoccupied by a growth of pine, followed in turn by a longer period during which a greatly diminished number of trees came in at irregular intervals. Hence the present stand is composed of three hypothetical classes, (1) older trees of the original stand and (2) seedlings that survived, and (3) reproduction following the disaster.

INTENSIVE MANURING OF PASTURES UNDER LOCAL CONDITIONS

The object of this experiment was to force the growth of grasses under permanent pasture during the rainy season and thus increase the stocking capacity of the pasture; a pasture consisting of Andropogon contortus. Andropogon pertusus, Digitaria sanguinale var. ciliaris and extensum and Indigoferas was selected for the experiment. This had received 3 cwts. of lime in 1927 and 20 cartloads of Farm Yard Manure, 3 cwts. of Bonemeal, and 1 cwt. of Suver phosphate in 1928. The ex- periment commenced in September 1929. Four acre plots (A, B, C and D) in one square block, were fenced off for the manuring experiment, and pasture all round the experimental block was used as control. The plots were fenced so that animals could gra rotati i. e. first A, second B, then G and lastly D, back to A and so on. The rains began on 14th September and the rainfall for the month was 701 inches. There were about 11 rainy days during the month.

A Uniformity Trial with Irrigated Broadcast Rice

This paper describes a uniformity trial with irrigated broadcast rice and shows the large inter- and intra-field variation which exists.The standard deviations decrease with the increased size of plots and vary from 20–1 per cent, with 1/436 acre plots to 7–8 per cent, with 1/22 acre plots.The decrease of the standard deviation is small with plots larger than 1/87 acre. This size of plot is considered to be the most practicable for field trials.The influence of proximity to bunds, irrigation channels and drains on increasing yields is discussed and methods of reducing errors due to this cause are suggested.It is shown that the use of a Latin square extending over more than one field has not produced a more accurate experiment than the use of randomised blocks. The latter method would therefore appear to be the more suitable for manurial and other trials, under the particular conditions of rice growing.

Three Years of Boll Weevil Control on One Twentieth Acre Plots, With Various Rates of Fertilizers

Three Years of Boll Weevil Control on One Twentieth Acre Plots, With Various Rates of Fertilizers