Rising Soil Temperatures Research Articles

ウンシュウミカンの栄養生長と花芽分化に及ぼす気温と地温の影響

One-year-old satsuma mandarin (Citrus unshiu Marc. cv. Okitsu Wase) trees budded onto trifoliate orange rootstocks were subjected to different soil temperature (15, 20, 25 and 30°C) and air temperature treatments (25°C in Experiment I, and 15 and 30°C in Experiment II) for 6 or 7 months. The effects of air and soil temperatures on vegetative growth and flower bud differentiation were investigated.The number of flushes and total length of the shoots increased with rising soil temperatures. When soil temperatures were above 20°C, the number of flushes at an air temperature of 15°C was less than at 30°C. The length of spring shoots at an air temperature of 15°C was longer than at 30°C. However, due to the trees at air temperature of 30°C having more growth cycle flushes, the total length of the shoots did not differ among treatments. The dry weight of the trees increased with increases in both air and soil temperatures. Both low air and low soil temperatures affected flower induction greatly. At an air temperature of 30°C, flower buds developed only at soil temperatures of 15 and 30°C. At an air temperature of 15°C, flower buds developed even when the soil, temperature was 30°C. Trees with air/soil temperatures of 25/30, 30/25 and 30/30°C did not bear any flower buds. The effects of temperature on mineral nutrient content were slight. The roles of soil and air temperature on vegetative growth and flower formation are briefly discussed.

ALFALFA FOOD RESERVES ESTIMATED CHEMICALLY AND BY ETIOLATED GROWTH

A 3-yr field study was conducted to compare two common methods of estimating stored food reserves in crowns and roots of alfalfa (Medicago sativa L.) during autumn and winter. A chemical method to measure total nonstructural carbohydrates (TNC) was compared with a method that measured total etiolated growth (TEG). No significant correlation was observed between the two methods. TNC increased during autumn, attained a maximum in midwinter and then declined in the spring in association with rising soil temperatures. In contrast, TEG attained a maximum in the fall and declined or remained at a steady level throughout the winter and during rapid growth in the spring. This suggests that not all TNCs in crowns and roots are used for growth of shoots. A significant and approximately constant level of TNC remained in the crowns and roots following completion of etiolated growth. Cutting frequency and cultivars significantly affected TEG and TNC values, but the specific information provided by each measurement remains to be elucidated.Key words: Alfalfa, food reserves, TNC, etiolated growth, clipping, crown buds

Environmental factors affecting seed germination of gray birch (Betula populifolia) collected from abandoned anthracite coal mine spoils in northeast Pennsylvania

SUMMARYGermination of gray birch (Betula populifolia) seed collected from anthracite mine spoils in northeastern Pennsylvania was studied. Environmental conditions of the spoil banks are such that high mortality may occur at seed and germination stages because of low moisture availability and thermal stress. The mine spoil banks are harsh environments with respect to key seed germination factors: percent soil moisture as low as 1.8% and soil surface temperatures reaching 59°C. In the field, gray birch typically germinated in mid‐April prior to severe environmental stress. Trends in germination success were inversely related to rising soil temperature and decreasing soil moisture availability. Although seeds were capable of survival and germination under laboratory conditions of constant temperatures in excess of 55°C, dramatic decline in germination was observed under fluctuating temperature regimes likely to be experienced in the field. No germinations occurred under fluctuating temperatures in excess of 30°C. Germinations in the field were seen to end after mid‐June when substrate temperatures exceeded 30°C.

Observations on the distribution of the pathogenMonosporascus eutypoides as related to soil temperature and fertigation

The possible role of rising soil temperatures and of fertigation in predisposing melon(Cucumis melo) and watermelon(Citrullus vulgaris) to the, thermophilic ascomyceteMonosporascus eutypoides is evaluated. Emphasis is placed on the possible involvement of advanced cultivation practices in changing plant environment and morphology. The geographical range of the organism in Israel is described. kg]Key Words: Cucumis melo; Citrullus vulgaris; Monosporascus eutypoides; soil temperature; fertigation; plastic mulch; tunnels; shoot:root ratio; water stress.

Emergence patterns of weed seedlings in relation to cultivation and rainfall

Summary:In experiments over 4 years, separate field plots were cultivated once only at 2‐week intervals and the weed seedlings recorded weekly. Soil disturbance resulted in a flush of seedlings of which 90% appeared within 10 weeks after cultivation in early spring and within 3 weeks after cultivation in summer. Weekly emergence then returned to the level prevailing on undisturbed soil. The species composition of the seedling populations varied with the time of year at which the soil was disturbed. In each year there was a spring flush of seedlings, probably associated with rising soil temperature; subsequent flushes were coincident on cultivated and undisturbed soil and were related to the rainfall pattern. In each year there were periods when lack of soil moisture restricted emergence, and this appeared to be the over‐riding factor determining seedling numbers. When cultivations were followed by long dry periods which prevented germination, the numbers of seedlings appearing when rain ultimately fell were no different from those when the soil was disturbed just before the rainfall.

Effects of Soil Temperature on the Development of Young Eggplants (Solanum Melongena)

The effect of different soil temperatures on the development of young eggplants was examined at extreme seasonal air temperatures. In winter, rising soil temperatures accelerated growth, but lowering the soil temperature in summer had no effect and extremely high soil temperatures caused very poor plant development.

The Influence of Root Temperature on Apple Trees. III. The Effect on Photosynthesis and Water Balance

SummaryOne-year-old M 2 apple trees were grown at three constant root temperatures (22°, 29°, and 36°C) in containers filled with either clay soil or a sandy loam.Rates of photosynthesis and transpiration measured four months after the start of the experiment decreased with rising soil temperature; the former more sharply in the sandy loam than in the clay soil. The potassium and chlorophyll content of the leaves decreased significantly with increasing soil temperature only from 29° to 36°C. Leaf water potential decreased, while the resistance of the leaf to the loss of water vapour, and the shoot : root dry weight ratio increased with rising temperature. The water content of the roots increased with rising temperature and that of the leaves decreased. The water content of both roots and leaves was as a rule lower in clay soil than in sandy loam.All these effects at 36°C soil temperature were significantly reduced by the application of potassium sulphate to the soil at the start of the experiment. The reducing sugar content of the leaves was not influenced by any of the treatments applied.The role of ethanol in apple leaves of plants subjected to supraoptimal root temperatures was investigated by immersing the root system of intact apple plants for 24 hours in a 5% ethanol solution. Compared with water-treated controls, the ethanol treatment reduced the rates of net photosynthesis, but did not affect the transpiration rate or the resistance of the leaf to loss of water vapour. Ethanol was recovered from the leaves of the treated plants.The reduction in the photosynthetic rate caused by supraoptimal root temperature was attributed to the direct effect of ethanol and to the closure of the stornata, caused by a low water potential of the leaves.

Persistence and degradation of chlorfenvinphos, chlormephos, disulfoton, phorate and pirimiphos‐ethyl following spring and late‐summer soil application

AbstractGranular formulations of chlorfenvinphos, chlormephos, disulfoton, phorate and pirimiphos‐ethyl were broadcast at 2 kg a.i./ha and incorporated to 100 mm into a sandy‐loam soil either in May or in September 1971. The relative persistence of their residues, including insecticidally active oxidation products, after both application dates was disulfoton > chlorfenvinphos > phorate > pirimiphos‐ethyl > chlormephos. When applied in September all the insecticides persisted for longer than when applied in May. Degradation was slower during the winter while the mean soil temperature at 100 mm depth remained below 6 to 7°C. Rising soil temperature in the following spring rapidly increased the rates of degradation of chlorfenvinphos, chlormephos and pirimiphos‐ethyl residues but not of disulfoton‐ and phorate‐derived residues, predominantly the parent sulphones, which had been leached deeper. Ten months after the September application, half the total residues derived from disulfoton and phorate were found below the initial incorporation depth, whereas the other insecticides showed relatively little downward movement. It was concluded that late summer/early autumn applications for carrot fly control would leave appreciable residues of some insecticides in the soil at the beginning of the next growing season which may contribute to the terminal residues in crops. These would be minimised if moderately persistent compounds were used or if doses of persistent ones were substantially reduced.

FIELD STUDIES OF THE SOIL ATMOSPHERE II. OCCURRENCE OF NITROUS OXIDE

SummaryStudies were made of the seasonal changes in the occurrence of nitrous oxide in the atmosphere of two clay soils. During the winter of 1971‐2 the nitrous oxide concentrations at both sites were in the range 20‐50 ppm. Levels increased with rising soil temperatures in spring, the mean values reaching 50‐170 ppm in May; some individual samples contained 1500‐6500 ppm. The level of nitrous oxide was inversely related to the oxygen content of the soil atmosphere and was also correlated with the nitrate and nitrite concentration of the soil water, but could not be correlated with either the proximity of field drains, soil moisture content or rainfall.

Statistische betrachtungen zur frage der abhängigkeit der nitrifikation von bodentemperatur und bodenfeuchtigkeit

By means of linear, linear-transformed and non-linear statements, the relationship is discussed between soil temperature and soil moisture on the one side and nitrification in the upper layers of a bare soil on the other. The results of the methods are compared. It is established that a non-linear model gives more information than any other. By means of the linear statements only the influence of soil temperature is discovered, whereas the non-linear model gives the combined action of soil temperature and soil moisture on the formation of NO 3-N. The non-linear model is based on a known model of the weather-yield statistics. By means of a square function, a hyperplane is fitted on the observed data and is resolved into components, resulting in a response hyperboloid, of which the surfaces of equal response are conic sections. By means of known formulae from analytic geometry, the Eigen-values and Eigen-vectors of the square form are calculated from the coefficients of the components to determine the type of the conic sections and they are used for criteria of the effectiveness of the parameters. The Eigen-vectors show that soil temperature and soil moisture are independent in their influence on the nitrification, while the Eigen-values indicate that the efficiency of the parameters is almost identical. The amount of NO 3-N increased with rising soil temperature. In the relation to soil moisture there is an optimum near the field capacity. Falling soil temperature in autumn and winter results in a decrease of NO 3-N, but only towards a fixed minimum. Calculations by use of the non-linear model result in a minimum of nearly 2 p.p.m., which is in conformity with common observations. A considerable increase of NO 3-N in spring, indicative of the beginning of micro-organic activity, results only after the soil temperature exceeds 5°C, even if the soil moisture is near the optimum. All results are valid only according the material used and are therefore to be regarded more qualitatively than quantitatively.

The effects of early season soil temperatures on emergence of summer crops on the north-western plains of NSW

The influence of early season soil temperatures on the extent and rate of emergence of five summer crops was examined using four sowings at weekly intervals between late September and late October. The crops were maize, grain sorghum, pearl millet, and two forage sorghums. Increasing soil temperature reduced the interval between sowing and first emergence, and gave variable results for the interval between first and final emergence. Percentage emergence of maize was high at all sowings, whereas that of all three sorghums was low at sowings with soil temperatures at 4 inches of below 65�F, but did not differ significantly between sowings at temperatures above 65�F. Emergence of pearl millet improved with each later sowing, but differences were not significant. Rate of emergence was accelerated by rising soil temperatures in the four days after first emergence, but subsequent effects after four days were generally minimal. Maize appeared to have a lower temperature requirement for emergence than grain and forage sorghums, which, in turn, showed a lower temperature requirement than pearl millet. From the results and other related data, it seems that maize can be sown with reasonable safety when four inch depth soil temperatures are 59� to 64�F (expected in late September), sorghums (both grain and forage) when this temperature is 65� to 69�F (expected in early- to mid-October), and pearl millet when it is 68� to 72�F (expected in early- to mid-November). The results support the concept of soil temperature being the best criterion to determine a safe time for early season sowing of summer crops.

Seasonal Feeding of Larvae of Ctenicera destructor and Hypolithus bicolor (Coleoptera: Elateridae) on Potatoes Placed in the Field at Weekly Intervals1

At Saskatoon, Saskatchewan, over 98% of the tunnels in potatoes, placed in the top 6 inches of soil for 1-week periods during the growing season, were caused by larvae of Ctenicera destructor (Brown) even though about 25% of the total population was Hypolithus bicolor Eschscholtz. Numbers of larvae of C. destructor decreased from early spring until late June or early July, mainly from mortality, and then increased with the appearance of newly hatched larvae. There was a further mortality of larvae from September to mid-October. The majority of larvae were in the top 6 inches of soil during the season, and not more than 5% were in the bottom 9- to 12-inch layer. Numbers of tunnels in the potatoes increased in general with rising soil temperatures in the spring, to a peak in early or mid-June. Alternate depressions and peaks followed, with peaks occurring in early or mid-July and early or mid-August, the last being the greatest. Tunneling then fell off to a low level by early or mid-September. Depressions in tunneling in mid-summer and after early fall were associated with low soil moisture and/or reduced temperatures, but the relationship between tunneling and concurrent soil temperature and moisture appeared to be different at different times of the season. It is suggested that previous food consumption and acclimation temperatures and moistures may influence this relationship, and that general molting of the larvae might bring about peaks and depressions of feeding at certain times. The possible importance of food plants in the fall to larval survival is discussed.