Content Of Available Nitrogen Research Articles

Pollution of intensively managed greenhouse soils by nutrients and heavy metals in the Yellow River Irrigation Region, Northwest China.

The present study aimed to assess the potential ecological risk of heavy metals and nutrient accumulation in polytunnel greenhouse soils in the Yellow River irrigation region (YRIR), Northwest China, and to identify the potential sources of these heavy metals using principal component analysis. Contents of available nitrogen (AN), phosphorus (AP), and potassium (AK) in the surface polytunnel greenhouse soils (0-20cm) varied from 13.42 to 486.78, from 39.10 to 566.97, and from 21.64 to 1,156.40mgkg(-1), respectively, as well as AP, soil organic matter (SOM) and AK contents tended to increase significantly at the 0-20- and 20-40-cm soil layers. Heavy metal accumulations occurred in the polytunnel greenhouse soils as compared to arable soils, especially at a depth of 20cm where Cd, Zn and Cu contents were significantly higher than arable soil. Cd and As were found to be the two main polluting elements in the greenhouse soils because their contents exceeded the thresholds established for greenhouse vegetable production HJ333-2006 in China and the background of Gansu province. It has been shown that Cd, Cu, Pb and Zn at the 0-20-cm soil layer were derived mainly from agricultural production activities, whereas contents of Cr and Ni at the same soil layer were determined by 'natural' factors and As originated from natural sources, deposition and irrigation water.

Differences in nitrogen‐assimilating enzyme activity in halophyte species are habitat‐related

AbstractThe chemical form and content of available nitrogen (N) in salt marsh substrates varies considerably. On the western coast of Ireland, habitats designated as Ombrogenic Atlantic salt marshes were formed on ombrogenic peat substrate. The peat substrate in these systems has three times more ammonium than substrate from adjacent salt marsh habitats on sand and mud substrate. This study examined the extent to which the high concentration of ammonium in peat salt marsh substrate influences the N‐ assimilating enzyme activity of halophytes and the extent to which N metabolism differs between species. Specifically, this work investigated whether plants from peat salt marshes are more likely to assimilate ammonium than plants from non‐peat substrates. Four halophyte plant species—Armeria maritima, Aster tripolium, Plantago maritime, and Triglochin maritime—were sampled from various saltmarsh habitats including three sites on peat substrate and three on non‐peat substrate, comprising sand, mud and sand/mud. The activities of N‐metabolising enzymes—glutamine synthetase (GS), glutamate synthase, glutamate dehydrogenase (GDH), and nitrate reductase (NR)—were quantified in shoot and root parts. Root GS activity in Armeria maritima and shoot GS activity in Triglochin maritima were positively correlated with increasing soil ammonium levels. Root NR activity in Aster tripolium and shoot NR activity in Plantago maritima were significantly higher in plants grown on non‐peat substrates than peat substrates. The shoot : root GS activity ratio in Triglochin maritima on peat substrate was more than double the ratio on non‐peat substrates. It is concluded that all species tested displayed differences in N‐metabolising activities depending on the chemical form and/or concentration of N in the substrate, while three out of the four species were capable of taking advantage of the high levels of ammonium in peat substrates.

Impacts of Close-to-nature Management Technology on the Korean Pine Soil Chemical Properties in Northeast China

Based on the guiding ideology of "Close-to-nature forestry", the soil chemical properties of Korean pine (Pinus koraiensis) plantation forest which was early done by canopy gap control were analyzed of Liangshui nature reserve in northeastern China. The results indicated that the nurture of forestry crevice diaphanous tended to improve the soil nutrient contents and significant differences of soil nutrients existed among different levels of soil for the same forest type of Korean pine. At 0< <TEX>$H{\leq}20$</TEX> cm layer, the content of available nitrogen, available phosphorus, available potassium, total nitrogen and total phosphorus in artificial pure Korean pine forest are 640.28 <TEX>$mg{\cdot}kg^{-1}$</TEX>, 7.54 <TEX>$mg{\cdot}kg^{-1}$</TEX>, 275.91 <TEX>$mg{\cdot}kg^{-1}$</TEX>, 1.114% and 0.075%, they all higher than the other kinds of forests and for average 1.1 times, 1.4 times, 1.3 times, 1.6 times and 1.2 times. From the layer of <TEX>$0</TEX><TEX><</TEX><TEX>H{\leq}20$</TEX> cm to 20 cm < <TEX>$H{\leq}40$</TEX> cm, soil nutrient indicators showed various degrees of decreasing in which organic matter had the greatest decline, decreasing by 170.64% while PH had the lowest decline, decreasing by 4.66%.

SIGNIFICANCE OF N-BIOFIXATION AND FOLIAR SPRAY WITH Zn AND Co ELEMENTS FOR IMPROVING FABA BEAN PRODUCTIVITY UNDER FIELD CONDITIONS OF MIDDLE NILE DELTA AREA, EGYPT

A field experiment was conducted on a clayey soil during twosuccessive winter seasons of 2007-2008 and 2008-2009 at Damas village, MitGhamer district, El Dakahlia Governorate, Egypt to evaluate the effectivenessof seed inoculation with rhizobium and foliar spray with zinc and cobalt onfaba bean (Vicia faba L.) yield and its components as well as seed protein andnutrient contents. Zinc and cobalt sulphates were applied at three rates of 0,250 and 500 mg L-1 for Zn and 0, 15 and 25 mg L-1 for Co. Yield and itscomponents (i.e., number of tillers plant-1), number & dry weight of nodulesand nitrogenase activity of root nodules plant-1 at two investigated periods of45 and 70 days from sowing as well as number of pods plant-1, grain contentsof protein and elements (i.e., N, P, K, Fe, Zn, Cu & Co). Soil content ofavailable nitrogen forms (NH4+ and NO3-) after 70 days from sowing and atharvest were taken into consideration in this study.The obtained data show that seed inoculation with rhizobiuminoculation and foliar spray with Zn and Co led to a significantly increased ineach of tiller plant-1, number of pods plant-1, grain protein, grain and strawyields in kg fed-1. A parallel trend was occurred for the positive effect of theapplied treatments on faba bean grain contents of N, K, Fe, Zn, Cu and Co,however, the greatest values were achieved at the highest rates of 500 and 25mg L-1 of Zn and Co, respectively. On the other hand, no changes wereobserved for grain content of P by increasing the applied Zn and Co rates,may be due to the antagonism between Zn and P.As for the beneficial effects of the applied treatments on the availablenitrogen content in the experimental soil, data show that seed rhizobiuminoculation as well as Zn and Co as foliar application resulted in a noticeableincrease for available content of nitrogen forms (NH4+ and NO3-) at bothinvestigated periods of 70 days after sowing and at harvest as compared to thecontrol treatment. At the same times, it is noticed that the available N-formsgave the greatest values at 70 days after sowing as well as in case of Znfoliarly as compared to at harvest and case of Co. This was true, since suchincrease was more closely to the nitrogenase activity. It is noteworthy tomention that seed inoculation and Zn or Co foliar application showed aparallel trend for the pronounced increases of all tested plant and soilparameters as compared to the control treatment under both studied growingseason conditions. So, it could be said that the residual effect of N-biofixation in the soil after harvest leading to rationalize use of N-mineralfertilizers for the next crop, which is surplus point for sustainable agriculturesystem.

CRUSHED ROCKWOOL AS A COMPONENT OF GROWING SUBSTRATES

CRUSHED ROCKWOOL AS A COMPONENT OF GROWING SUBSTRATES

Effects of earthworm activity on fertility and heavy metal bioavailability in sewage sludge

The potential for using earthworms ( Eisenia fetida) to improve fertility and reduce copper and cadmium availability in sewage sludge was tested by laboratory incubation experiments. Results comparing sewage sludge with and without earthworm treatment showed that earthworm activity decreased the contents of organic matter, total nitrogen, but increased the contents of available nitrogen and phosphorus and had no significant effect on the contents of total phosphorus, total potassium and available potassium. After incubation of the sewage sludge with earthworms for 60 days, the contents of Cu and Cd in the earthworms increased with the increase of additional Cu up to 250 mg kg − 1 and Cd up to 10 mg kg − 1. Bioconcentration factors (BCF) were higher than 1 only for Cd when the addition rate was lower than 5 mg kg − 1, which indicates that the earthworms can only accumulate Cd when the concentration of Cd is low in sewage sludge. Bioavailability of Cd and Cu was evaluated by applying sewage sludge with and without earthworm treatment to soil and then growing cabbage plants. The results showed that earthworm treatment increased the biomass of cabbage and decreased the bioaccumulation of Cd and Cu in the cabbage plants.

Aerobic and anaerobic incubation: Biological indexes of soil nitrogen availability

Our researches have been made on brown forest soil that had been used in long-term experiments set up according to specified fertilization system for over 30 years. We have chosen those experiment variants in which quantities of nitrogen fertilizers were gradually increased. The soil samples taken from 0 cm to 30 cm depth were used to determine biological indexes of nitrogen availability (aerobic and anaerobic incubation). The same samples were also used for pot experiments with oat. Plant and soil parameters obtained in controlled conditions were used for determination of biological indexes reliability in measuring the soil nitrogen availability. On the grounds of correlation analysis, it can be concluded that biological index of nitrogen availability achieved by the anaerobic incubation (without substraction of the initial content of available nitrogen) of the investigated brown forest soil is the reliable indicator of soil nitrogen availability. That is not the case with the aerobic incubation in which reliability has not been established.

The determination of potential ammonification in soil by arginine method

In this paper investigations were carried out on two soil types (vertisol and brown forest soil) with different doses of applied N-fertilizer: diameter, N60 N90; N120 and N250. The potential ammonification in soil was obtained by arginine method. The following properties of soil were determined: pH value organic C, available NH4-N and mobile-Al. The pH value in vertisol was 3.75-4.07; mobile-Al was 0.67-4.90 mg/100g; % organic C 1.38-1.46 and the content of available nitrogen was 4.4-11.2 ppm. The amount of released NH4-N by arginine ammonification in this soil type was very low [(-0.12)-0.27mg/g-1h-1]. Correlation coefficients between released NH4-N from arginine and soil pH were (-0.96*), mobile Al - (-0.99**), applied fertilizer doses - (-0.95*). In brown forest soil the amount of released NH4-N by arginine ammonification was greater than in vertisol, ranging from 3.16 to 7.11mg/g-1h-1. Correlation coefficients between soil properties and released NH4-N from arginine were not statistically significant.

RELATION OF AVAILABLE SOIL NITROGEN TO RICE YIELD

Thirty-one surface soil samples from nine years of rate and ratio rice fertilization experiments at different locations in Louisiana were analyzed for their available-nitrogen content, using six chemical and two biological extraction methods. The relationship between the available soil nitrogen and rough rice yields was then investigated. Total soil nitrogen varied widely, ranging from 540 to 5460 parts per million. The average percentage recovery of total soil nitrogen (representing the available soil nitrogen), as determined by the various methods used, also ranged widely, from as high as 16.74 percent, by the hot alkaline permanganate method, to the lowest value of 1.08 percent, by boiling soils in 0.01 M CaCl2 solution. Good correlation coefficients were obtained, especially among the anaerobic incubation and each of the other extraction methods used. The acid hydrolysis method correlated the least with the other extraction methods. Highly significant correlation coefficients were obtained between the rough rice yields from the untreated plots (plots that received no nitrogen) and the available soil nitrogen determined by all the extraction methods. The best correlation was obtained with the anaerobic incubation method (r = 0.622). The rough rice yield in plots receiving 56 or more kilograms of nitrogen per hectare did not exhibit a significant relationship with the available soil nitrogen. Relationships between the rough rice yields at zero and 28 kg/ha N and the available soil nitrogen, as determined by the anaerobic incubation method, were better described by curvilinear models than by linear ones. The relationship was also established between yield increase from application of 112 kg/ha N (the level of nitrogen generally considered near optimum for rice in Louisiana) and available soil nitrogen determined by the anaerobic incubation method. With some reasonable degree of accuracy, yield increase could be predicted from the graph signifying this relationship.

Predicting Nitrogen Fertilizer Needs of Iowa Soils: IV. Evaluation of Nitrate Production as a Criterion of Nitrogen Availability

AbstractPreceding papers in this series have traced the development of a suitable method for assessing the relative nitrogen‐supplying power of soils and its correlation with crop response to nitrogen fertilization in the field. This method has been shown to be of value in predicting the need for nitrogen fertilizer in Iowa soils.The present study, conducted under controlled greenhouse conditions, was designed to evaluate critically the utility of soil nitrate release as a basis for establishing the relative nitrogen status of soils. The 21 soils used in this investigation represent a wide range in nitrogen‐supplying capacity. Four levels of nitrogen fertilizer were applied to pots and German millet was grown.The relation between total nitrogen uptake by the crop and level of applied nitrogen was linear for all soils studied. Extrapolation of the linear regressions provided values which reflected the relative contents of available nitrogen in the soils. These values which have been termed “N‐values” are expressed in units of applied nitrogen. Also, N‐values correlated highly with the total nitrogen uptake of the check pots. Both N‐values and nitrogen uptake by the plants were highly correlated with nitrate nitrogen released during a 2‐week period of incubation. Considerably lower correlations were found in relating these criteria to total soil nitrogen or to values obtained by the alkaline permanganate method.