Input–Output Budgets of Major Ions for a Forested Watershed in Western Maryland

Water, Air, &; Soil Pollution - We measured concentrations and fluxesof major ions in wet deposition, throughfall andstream water in a forested watershed on the AlleghenyPlateau of western...     

Soil Total Nitrogen and Natural 15Nitrogen in Response to Long-Term Fertilizer Management of a Maize–Wheat Cropping System in Northern China

The Fengqiu long-term field experiment was established to examine effects of organic manure and mineral fertilizers on soil total nitrogen (N) and natural ¹⁵N abundance. Fertilizer regimes include organic manure (OM), one-half N from organic manure plus one-half N from mineral N fertilizer (1/2OMN), mineral fertilizers [N–phosphorus (P)–potassium (K), NP, NK, PK], and a control. Organic manure (OM and 1/2OMN) significantly increased soil total N and δ¹⁵N, which was expected as a great amount of the N applied remained in soils. Mineral NPK fertilizer and mineral NP fertilizer significantly increased total N and slightly increaed δ¹⁵N. Phosphorus-deficient fertilization (NK) and N-deficient fertilization (PK) had no effect on soil total N. Significantly greater δ¹⁵N was observed in the NK treatment as compared to the control, suggesting that considerable N was lost by ammonia (NH₃) voltalization and denitrification in this P-deficiency fertilization regime.     

Influence of Organic Matter Vis-à-Vis Humic Acid on the Transformation of Inorganic and Organic Forms of Nitrogen in a Typic Haplustept Soil

A laboratory experiment was conducted to study the changes in inorganic and organic forms of nitrogen (N) in a Typic Haplustept soil treated with mustard cake vis-à-vis humic acid in the presence and absence of inorganic N. Results revealed that irrespective of treatments, significantly higher amount of soluble nitrate (NO₃^-), hydrolysable ammonium (NH₄⁺), non-hydrolysable and total N were accumulated in the soil treated with mustard cake in the presence of inorganic N. However, on the other hand, a humic acid-treated system showed significantly higher content of exchangeable NH₄⁺ and hexosamine N. Application of humic acid alone leads to the accumulation of a significantly higher amount of total hydrolysable and unidentified N in the soil. Among the different treatments, NH₄⁺ fixation was more in mustard cake followed by humic acid-treated soil. Humic acid is more susceptible to mineralization than mustard cake, particularly with respect to total N accumulation in soils.     

Vertical Distribution of Sulfur Fractions in a Continuously Fertilized Acid Alfisol Under Maize​–Wheat Cropping System

Vertical distribution of sulfur fractions was studied in a long-term fertilizer experiment at the experimental farm of Department of Soil Science, Himachal Pradesh Agricultural University, Palampur (India), comprising various combinations of fertilizer and amendments. Initially, available nitrogen (N) was high, and phosphorus (P), potassium (K), organic carbon were optimum. Different forms, viz., available, water-soluble, heat-soluble, organic, and total sulfur were significantly affected by continuous cropping and decreased with depth. However at surface layer, 100% NPK(-S) resulted in 67%, 70%, 34%, 47%, and 48% reduction in these fractions, respectively, as compared to 100% NPK. Among all, organic sulfur was recorded highest. Hundred percent NPK + farmyard manure (at par with 100% NPK + lime) recorded highest maize and wheat yield. Hundred percent NPK(-S) recorded 39% and 44% reduction in grain yield of maize and wheat as compared to 100% NPK, respectively. Sulfur fractions were positively and significantly correlated with yield of maize?–wheat which shows the importance of sulfur fertilization.     

Dissolved Organic Matter (DOM) in Acid Forest Soils at Gådsjön (Sweden): Natural Variabilities and Effects of Increased Input of Nitrogen and of Reversal of Acidification

Effects of (1) the addition of 35 kg N ha^-1yr^-1(as NH₄NO₃) and (2) interception of throughfall and litterfall by means of a roof on concentrations, chemical characteristics and dynamics of dissolved organic matter (DOM) in acid forest soils (podzols) were studied at Gårdsjön, Sweden. A non-manipulated catchment served as a reference. After 4 yr of treatment no significant effects of either manipulation were found on concentrations and characteristics of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON). The variability of these parameters within catchments appeared to be of the same order of magnitude as the variability between catchments. At all sites, DON contributed more than 70% of the total dissolved nitrogen. In general, the proportion of hydrophilic DOC increased with depth. In contrast, to other studies the C/N ratio of DOM at Gårdsjön did not show a clear pattern with depth. Other studies in SE U.S.A. have suggested that relatively low C/N ratios at depth are due to increased contribution of hydrophilic neutrals to DOC. However, this fraction appears to be small in temperate and boreal spruce forest soils, including Gårdsjön.     

Optimizing Nitrogen Fertilizer–Use Recommendations for Winter Wheat in a Mediterranean‐Type Environment using Tissue Nitrate Testing

Abstract

Although nitrogen (N) fertilizer use is essential for economic yields of modern field crops, whether rainfed or irrigated, the underlying concern is to maximize nutrient‐use efficiency and avoid excessive N use that results in deterioration of water quality from the environmental standpoint as well in the interest as human and animal health. Soil testing for N forms and total plant N analysis can contribute to the efficient use of N, but both strategies have limitations. Accordingly, tissue testing of the growing crop has been promoted as an alternative approach. Although such tests have been widely used in the West to monitor the N status of crops, they are rarely used in developing countries. A 2‐year field trial examined the potential of tissue testing of rainfed wheat in a typical Mediterranean environment in the Cukurova region of southern Turkey, because observations from wells in the region had suggested increasing and excessive nitrate levels, most probably from fertilizer N use. The trial, in essence, compared different levels of N fertilizer application based on farmers' traditional application in addition to considering soil mineral N with tissue N based on a color index to refine N application recommendations. The measurements were taken in conjunction with observations on wheat yields. The study showed that using the combined approach of soil and tissue nitrate resulted in lowering the N fertilizer recommendations without any lowering of crop yields, clear evidence that farmers had been using excessive amounts of fertilizer N in the absence of limited or no official guidelines. Thus, such tests should be promoted to replace traditional fertilizer application practices as a simple and easily used tool to improve N‐use efficiency for the farmer, in addition to reducing negative environmental impacts of such use. The quick tests can help promote the awareness of the potential negative effects of overuse of N fertilizer.