Does the potential ammonium fixation of soils have an impact on the optimum nitrogen fertilizer rate?

Field experiments were conducted to determine the effect of nitrogen (N) fertilizer forms and doses on wheat (Triticum aestivum L.) on three soils differing in their ammonium (NH₄) fixation capacity [high = 161 mg fixed NH₄-N kg^?1 soil, medium = 31.5 mg fixed NH₄-N kg^?1 soil and no = nearly no fixed NH₄-N kg^?1 soil]. On high NH₄⁺ fixing soil, 80 kg N ha^?1 Urea+ ammonium nitrate [NH₄NO₃] or 240 kg N ha^?1 ammonium sulfate [(NH₄)₂SO₄]+(NH₄)₂SO₄, was required to obtain the maximum yield. Urea + NH₄NO₃ generally showed the highest significance in respect to the agronomic efficiency of N fertilizers. In the non NH₄⁺ fixing soil, 80 kg N ha^?1 urea+NH₄NO₃ was enough to obtain high grain yield. The agronomic efficiency of N fertilizers was generally higher in the non NH₄⁺ fixing soil than in the others. Grain protein was highly affected by NH₄⁺ fixation capacities and N doses. Harvest index was affected by the NH₄⁺ fixation capacity at the 1% significance level.     

Comparison of buffet and à la carte serving at worksite canteens on nutrient intake and fruit and vegetable consumption

OBJECTIVE: To evaluate the nutritional composition of worksite canteen lunches and to examine the impact of two meal serving systems on employee intake, i.e. buffet style with a fixed price for a varied number of dishes and à la carte style with a separate price for each item on the menu. DESIGN: Laboratory technicians observed employees' food selection and collected identical dishes. Food items were weighed separately to calculate the content of fruit and vegetables. The content of protein, fat and ash of each dish was chemically analysed and the carbohydrate and energy content calculated. SETTING: Fifteen randomly chosen worksite canteens in Denmark: eight canteens serving buffet style and seven canteens with an à la carte line. SUBJECTS: one hundred and eighty randomly chosen employees having lunch at the worksite canteens. RESULTS: The average percentage energy from fat was 37 +/- 12 among men and 33 +/- 12 among women. No association was found between the meal serving system and energy intake or macronutrient composition. Eating at canteens serving buffet style, on the other hand, was associated with an increased intake of fruit and vegetables, on average 76 g, and a lower energy density of the food for both genders. CONCLUSION: The results highlight the possibilities of promoting healthy food choices in the catering sector and the need to identify models of healthy catering practice. Serving buffet style appears to be a promising strategy in order to increase fruit and vegetable consumption in food served away from home.     

Comparison of preplant and fertigated micronutrients on the growth of the Hebe ’inspiration’

Abstract

Micronutrients may be provided to plants in containers either via pre‐plant inclusion in the growing medium or via fertigation, or both. For Hebe ’Inspiration’ plants growing in a soilless potting medium, micronutrients applied as a single pre‐plant application or via weekly liquid fertilizer applications were equally effective in producing optimum growth over a 12‐month period. Under the conditions of this experiment, the liquid fertilizer did not need to contain more than (in mg/L) 0.5 = iron (Fe), 0.1 = copper (Cu), 0.1 = zinc (Zn), 0.8 = manganese (Mn), and 0.1 = boron (B). Growth was excellent for the full 12 months, without supplementation via the liquid fertilizer, when there were micronutrient concentrations of (in mg/L extract) 29 = Fe, 0.5 = Cu, 3 = Mn, 0.6 = Zn, and 0.14 = B in a 1:1.5 volume in a 2mM DTPA extract of the medium at potting.     

The effect of gypsum and other salts on the growth of narrow‐leafed lupins

Abstract

Glasshouse experiments were conducted to establish the cause of poor lupin growth in the presence of gypsum in field trials which had been conducted in Western Australia. In the first experiment, Bradyrhizobium‐inoculated lupins were grown in nutrient solutions with varying concentrations (1, 3, 5, and 10 mM) of calcium (Ca) and sulfate (SO₄) added as either CaSO₄, K₂SO₄, or CaCl₂ to establish whether gypsum caused Ca or SO₄ toxicity to the plants. Although a general decrease in lupin plant growth was observed as the concentration of each salt increased, there was no evidence that either Ca or SO₄ directly caused toxicity to the plants. Two soil experiments were therefore conducted to investigate lupin growth responses to the salts in a soil environment. The first soil experiment was conducted in a yellow earth— the same soil in which lupins had been adversely affected by gypsum in the field. The second soil experiment was conducted in the topsoil of a siliceous sand. Basal nutrients and different rates of CaSO₄, K₂SO₄, and CaCl₂ were added so that similar amounts of Ca and SO₄ were present for each treatment at a given application rate. In both soils, lupin growth generally decreased as the application rate of treatments increased, although the magnitude of the decrease in growth was higher in the yellow earth than the siliceous sand. The strongest correlation between lupin growth and a soil solution chemical property was a log‐linear relationship between the shoot or root dry weight and the electrical conductivity (EC) of the soil solution. Plant nutrition was affected by different treatments, particularly with respect to nutrient balances. It is suggested that a high ionic strength in the soil, which results when gypsum is applied in the field, may contribute to the lupin yield decline. Possible reasons for the effect are discussed.     

Tillage – impact on infiltration of the Loess Plateau of China

In arid and semiarid regions, water infiltration is often affected by the soil surface conditions, such as the soil crusts and soil roughness. The objective of this laboratory study was to assess the effects of soil crusts and tillage treatments on soil infiltration in the Loess Plateau of China. A simulated rainfall storm at 80 mm h^?1 rate was applied to soil boxes set to slopes of 5°, 10°, 15° and 20° with two soil surface conditions (crusted and uncrusted) and three tillage treatments (contour tillage [CT], artificial digging [AD] and straight slope [SS]) to investigate the infiltration rates. The results show that the infiltration rate was always lower under the SS treatment than under the CT and AD treatments. The time interval to the steady state was shorter under the SS (10 min) than under the CT and AD treatments (15–20 min). The final infiltration rate was nearly the same under the CT treatment and AD treatment; whereas, the SS treatment resulted in the lowest final infiltration rate. The infiltration rates were always greater in soils without crusts than in soils with crusts. The slopes, soil crusts and tillage treatments had significant (p < 0.001) effects on the cumulative infiltration rates. The combined effects of the slopes and tillage treatments on the cumulative infiltration rates were much more significant (p < 0.01) than the other combined effects (p < 0.05).     

The impact of earthworms on the abundance of Collembola: improvement of food resources or of habitat?

I assessed the direct influence of earthworm excretions, and the impact of earthworms through their action on the soil structure (increased macroporosity), on the population dynamics of the collembolan species Heteromurus nitidus. The intestinal content of Collembola arising from cultures on different soil types was observed, and two experimental cultures of H. nitidus were run: (1) a culture performed on an inert substrate supplied either with earthworm casts or with soil as food resource, (2) an experiment using microcosms with cores of two humus forms (moder and calcic mull), in the presence or absence of earthworms. The observation of gut contents revealed that H. nitidus feeds on excrements, the composition of which (ratio organic matter/mineral matter) varies according to the humus form where it lived. Slightly aged (10–15 days) organo-mineral casts of earthworms appeared to be a better food than calcic mull aggregates or organic material from moder. Densities of H. nitidus cultured in cores of calcic mull were higher than in moder, except when cores of moder were inhabited by an anecic earthworm for 2 months. The humus form strongly influenced populations of H. nitidus, firstly because densities of predators were higher in moder than in calcic mull, and probably also because of soil macroporosity. It was concluded that earthworms would affect predation on H. nitidus by creating a network of interconnected macropores in which Collembola can move and find shelter.     

Effect of nitrogen on the growth and photo‐synthetic activity of salt‐stressed barley

Pot experiments were conducted in the greenhouse to study the effect of nitrogen (N) nutrition on photosynthesis and water relations of barley plants under salinity conditions. Nitrogen decreased the sodium (Na) content and increased the potassium (K) content in shoots. The net photosynthetic rate of leaves increased significantly with added N increasing from 0 to 100 mg N/kg soil. The activity of ribulose 1,5 bisphosphate carboxylase (RuBPC_ase) in leaves of high‐salt plants was lower, and in leaves of the low‐salt plants higher than that in control plants. The photosynthetic rate was reduced by sodium chloride (NaCl) and was significantly correlated with total soluble protein per unit leaf area. At each N level, stomatal conductance in leaves was reduced considerably by salt. Proline content of leaves increased with increasing N level. It was higher in leaves of salt‐treated plants than in those of control plants. The osmotic potential of leaves decreased with increasing N applied, and the turgor pressure of high N plants remained higher under salt treatment condition.     

Does the Ammonium Fixation Capacity of Soils Have a Significant Effect on the Nitrogen Nutrition of Wheat?

Pot experiments were conducted on three soils differing in their ammonium (NH₄ ⁺) fixation capacity [high = 161 mg NH₄-nitrogen (N) kg^?1 soil; medium = 31.5 mg NH₄-N kg^?1 soil; and no = no NH₄-N was additionally fixed], and the effect of N fertilizer forms and doses on wheat (Triticum aestivum L.) was investigated. Grain yields responded to almost all forms of N fertilizer with 80, 160, and 240 kg N ha^?1 in the high, medium, and no NH₄ ⁺ fixing soil process, respectively. Agronomic efficiency of applied N fertilizers was significantly greater in the no NH₄ ⁺ fixing soil. Thousand grain weights (TGW) of wheat grown on the high and medium NH₄ ⁺ fixing soil decreased with increasing N. Grain protein increased with increasing NH₄ ⁺ fixation capacity. Nitrogen doses and the forms of N fertilizers affected grain protein at a significance level. The combination of urea + ammonium nitrate (NH₄NO₃) was most effective in increasing grain protein content.     

The influence of the herbicide paraquat ‘Gramaxon’ on growth and metabolic activity of three chlorophytes

The acute toxicity of commercial herbicide, Paraquat was determined by 96-hr static bioassay on the freshwater chlorophytes Scenedesmus dimorphus (Trup.) Kuetz., Scenedesmus quadricauda (Trup.) de Brebisson and Ankistrodesmus falcatus (Cord) Ralfs. The 96-hr EC50 values of Paraquat for reducing growth and metabolic products of the three algae were determined. The number of days required for cell division increased with increasing Paraquat concentration. The three algae and their test parameters respond differently to Paraquat. Scenedesmus dimorphus was the most susceptible alga and the chlorophyll a was the most sensitive response parameter. On the other hand, the dry weight of the test algae was the most resistant parameter. It was observed that Paraquat has inhibitory effect on the primary producers.     

Effect of crop load on hardiness,protein and amino acids content of apple flower buds at the wintering stage and the begining of the growth∗

The cold tolerance of flower buds of apple Malus domestica Borkh. ('Mclntosh'/M.7) declined during spring growth. The absence of fruit in the previous year increased the ability of the buds to withstand lower temperatures. All flower buds retained the capacity to tolerate freezing injury until first pink stage. The median lethal temperature (MLT) of the flower buds increased relatively throughout the sampling period. The flower buds of cropped trees were more susceptible to low temperature injury during spring at all stages of development. The flower buds of non‐cropped trees contained higher levels of hydrophilic and acidic amino acids from October until April, which may be related to their greater cold tolerance. A new nitrogen:protein conversion factor (5.51) was calculated based on total amino acid analysis which could be substituted for 6.25 as a means of estimating total protein content of apple flower bud tissue using the Kjeldahl method.     

Relative effectiveness of phosphorus on narrow‐leaf and broadleaf birdsfoot trefoil growth and the effect of added phosphorus on vesicular arbuscular mycorrhizal infection

The relative effectiveness of phosphorus (P) applications on growth and the effect of added P on the extent of infection of roots of narrowleaf birsfoot trefoil (Lotus tenuis) and of broadleaf birdsfoot trefoil (Lotus corniculatus) by an indigenous VAM fungi (Glomus sp.) was studied on a P‐deficient soil (Typic Natraquoll). In terms of rate of increase of shoot growth per unit of added P, broadleaf was more efficient than narrowleaf birsdfoot trefoil but they did not differ in the relative effectiveness of P for growth. For the two Lotus species, when increasing the level of added P there was an initial increase in the percentage of root length infected, and then with further additions, there was a consistent decrease of the infection. For narrowleaf, the maximum percentage of root length infected was when plants reached 11% of their maximum shoot growth. Whereas for broafleaf, the maximum percentage of root infected was when plants reached the 66% of their maximum shoot growth. Despite differences in both, the shape of the response curve of shoot growth to P and the extent of infection between Lotus species, they did not differ in their ability to utilize the P that had reacted with the soil for a period of time.     

Effects of vesicular‐arbuscular mycorrhizas and phosphorus on water status and growth of apple

Apple (Malus hupehensis Rehd) seedlings were grown in sterilized and non‐sterilized soil with or without phosphorus (P) added and inoculated by VA mycorrhizal (VAM) fungi (Glomus versifome Daniels et Tappe and Glomus macrocarpum Tul et Tul). In sterilized soil, the VAM infection increased the transpiration rate (Tr.) of the leaves, reduced the stomatal resistance (Sr.) and the permanent wilting percentage (PWP) and enhanced the rate of recovery of the plant from the water stress and the plant growth (e.g. leaf number, stem diameter and dry weight). It also increased absorption of most minerals, especially Zn and Cu by the roots and weakened the P‐Cu and P‐Zn interactions. Phosphorus fertilization had some positive effects on the water status, P nutrition and growth, but it reduced the Cu concentration. VAM improved the water status and enhanced drought tolerance of the trees by enhancing absorption and translocation of water by the external hyphae. The efficiency of inoculation in nonsterile soil was not obvious.     

Studies on soil fumigation—I: Effects on ammonium,nitrate and phosphate in soil and on the growth,nutrition and yield of wheat

Fumigation of field soil with chloropicrin alone or followed by methyl bromide, each at 220Kg·ha^?1, released 20–30 parts/10⁶ NH⁺₄-N which persisted for 75 days; such fumigation also doubled the amount of bicarbonate-extractable phosphate 28 days after fumigation. Soil fumigation increased both the vegetative and grain yields as well as increasing the content of N in the grain and the content of K and Cl in the tops at ear emergence. Root growth and the phosphate uptake activity of the roots were increased by soil fumigation.     

Effect of nitrogen form ratio on pansy growth and nutrition and the palatability to white‐tailed deer

Abstract

Pansies are one of the most popular annual bedding plants in the United States. Growth and uptake of essential nutrients as influenced by N‐form ratio was evaluated in pansy as well as what role pansy nutrition plays in the protection of pansy against feeding damage by white‐tailed deer provided by selected repellents. Plants were grown under three N‐form ratios: 100:0, 50:50, and 0:100NO₃:NH₄. Dry weight was highest for pansy treated with 100:0 and lowest for plants treated with 0:100 NO₃:NH₄ Mean quality ratings were 4.07 for pansies grown with 100:0,1.80 for pansies grown with 50:50, and 0.78 for pansies grown with 0:100. Potassium (K), magnesium (Mg), and manganese (Mn) content was lower in plants treated with 0:100 than in those treated with 100:0. Ammonium may have competed with these cations for uptake. Boron (B), copper (Cu), molybdenum (Mo), and aluminum (Al) content was highest in plants treated with N‐NH₄. There was no significant difference shown in nutrient levels caused by repellent treatments. Feeding damage was shown to be affected by N‐form ratio only on Day 3 of the study. Of the three repellent treatments [Deer and Rabbit Repellent (Thiram), Deer Away purrescent egg spray, and no spray], Thiram provided the greatest protection to pansies over the study period.     

Is there an impact of climate change on soil carbon contents in England and Wales?

It is not yet clear how soils are responding to a warming climate. A major study using the National Soil Inventory (NSI) of England and Wales reported large declines in soil carbon concentration across 11 land uses between 1978 and 2003 and concluded there was a link to climate change. However, a second, almost contemporary study, recorded no significant changes, raising the possibility that the reported declines were caused by changes in land use and management rather than by climate change. We have used ‘space‐for‐time’ substitution on the data from the initial NSI study, combined with changes in rainfall and temperature over the survey period, to determine the extent to which the declines in soil carbon observed in the second NSI study could be predicted from changes in climate. For organo‐mineral and mineral soils, little (0–5%) of the observed decline in carbon concentration can be predicted from changes in climate. In contrast, 9–22% of the changes reported for organic soils in semi‐natural habitats are consistent with changes in temperature and rainfall between the two NSI surveys. We also found that carbon concentration in organic soils in semi‐natural habitats declines as temperatures exceed 7°C, mirroring independent observations for the decline in bog and dense shrub moor vegetation as temperatures rise above 7°C, and raising the possibility that climate change may influence soil carbon indirectly by changing vegetation cover, and hence litter quality.