Nitrogen balance in small river basins under agricultural and forestry use

The N balance has been studied in detail in the basins of small rivers under agricultural management and forest use. The N content of the watershed territory of large forests was found to be practically balanced. In the river basin where the land was intensively farmed for 10 yr, N input increased five times through mineral fertilizers, and one-and-a-half times through organic fertilizers. Consequently, the amount of N returned to the atmosphere as a result of denitrification increased by one-and-a-half times, and that leached into the ground water, increased from 0.8 to 6.5 mg 1^?1 N.     

Air filter efficiency as a function of particle size and velocity

The air filtration theory demonstrates the existence of a minimum efficiency value for some aerosol particle sizes and velocities. Through experiments, many laboratories have sought to prove this efficiency minimum while using industrial filter pads. Generally used methods, involving monodisperse aerosol generation, are difficult to implement. The authors describe a laboratory experiment ready for semi-industrial application, thanks to the use of a new type of particle counter. A lightly poly dispersed soda-fluorescein (uranin) aerosol is used. Air filtration concepts are brought to mind and detailed experimental models are described, as well as findings with high-efficiency paper filters, alfa fiber filters, asbestos and fiberglass filters. Efficiency minimum occurs for 0.15 μm diameter sodafluorescein particles. Filtration velocity influence on efficiency is also demonstrated. Lastly, the authors compare known results with their soda-fluorescein aerosol and with sodium chloride aerosol findings.     

Run-off transport of herbicides during natural and simulated rainfall and its reduction by vegetated filter strips

The efficiency of filter strips in protecting watercourses against herbicides in run‐off was evaluated in field experiments in western Germany. Surface run‐off caused by natural rainfall and related transport of metolachlor, terbuthylazine and pendimethalin were measured on plots of 40 m length without filter strips (F0), and after passing over three types of herbicide‐untreated field margin: 12 m conservation headland (CH12), 6 m (GF6) and 12 m grass strips (GF12). Run‐off was also measured after simulated rainfall on 7 m long plots without (F0) and with 3 m grass strips (GF3). All three herbicides were transported both in dissolved and in adsorbed forms; the partitioning depended on their water solubility with metolachlor and terbuthylazine mainly translocated in dissolved form (F0: highest mean concentrations for a natural run‐off event 721 and 220 μg L^?1, respectively). Pendimethalin was predominantly transported in adsorbed form (maximum mean concentration 11.2 μg L^?1). In the sediment, the highest mean herbicide contents in a single natural event (F0) accounted for 2294 μg kg^?1 (metolachlor), 1317 μg kg^?1 (terbuthylazine) and 5648 μg kg^?1 (pendimethalin). The proportions of applied herbicide translocated were 0.3% (metolachlor), 0.2% (terbuthylazine) and 0.06% (pendimethalin; F0, natural rainfall). The extent of herbicide transport decreased with time but within this trend soil sealing, soil moisture and amount and intensity of rainfall increased losses. Compared with the F0 plots, the reduction of herbicide translocation after natural rainfall reached 80–83% (CH12), 80–88% (GF6) and >99% (GF12) over the 3‐year period. The 12 m grass strips allowed only one extreme run‐off event to pass through, thus providing a highly effective watercourse protection against herbicide pollution.     

Surface runoff and seed trapping efficiency of shrubs in a regenerating semiarid woodland in northern Ethiopia

In forest restoration areas in northern Ethiopia, natural regeneration of Olea europaea ssp. cuspidata only occurs under pioneer shrubs. To assess the impact of erosion on the spatial distribution of Olea recruits, secondary dispersal of olive seeds by surface runoff was determined in and near the micro-environment of two important pioneers (Acacia etbaica and Euclea racemosa). We hypothesized that (1) Olea seeds deposited under the protective crowns of shrubs are less likely to be lost by surface wash than seeds in the bare inter-plant areas and (2) that seeds in the latter are more prone to be translocated by runoff to microsites under shrubs than to open areas.     

Arbuscular mycorrhiza improves nitrogen use efficiency in soybean grown under partial root-zone drying irrigation

Arbuscular mycorrhizal (AM) fungi can form symbiotic association with the roots of plants that acquire carbon (C) exclusively from the host plants and supply nitrogen (N) to the plants. In this study, our objective was to investigate the effects of the AM fungus on plant growth, C and N partitioning and accumulation of Glycine max L. grown under water stress in pot experiment. Soybean seedlings were inoculated or not inoculated with the AM fungus, and were exposed to three irrigation treatments including full irrigation, deficit irrigation and partial root-zone drying irrigation (PRD). The ¹⁵N isotope labeling was used to trace soybean N accumulation. Results showed that water stress significantly decreased plant dry weight. Compared with non-AM fungus, AM fungus increased root N and ¹⁵N concentration, and decreased stem, leaf and pod N and ¹⁵N concentrations under PRD. AM colonization decreased C and N partitioning into stem and leaf, and increased C and N partitioning into root under PRD. AM plants had greater C accumulation and N use efficiency than non-AM plants. It was concluded that AM symbiosis plays an important role in C and N dynamics of soybean grown under water stress.     

Relationship between nitrogen accumulation and nitrogen use efficiency of rice under different urea types and management methods

We aimed to clarify the effectiveness of polyaspartic acid (PASP)-urea on nitrogen (N) accumulation and N use efficiency in rice. We compared PASP-urea with conventional urea with two N management methods (farmer’s fertilizer practice and optimized N management) in Wenjiang, Sichuan Province, China, in 2014 and 2015. N recovery efficiency (NRE), N agronomic efficiency (NAE), and N partial factor productivity (PFP) decreased with increasing N uptake by the shoot and the stem plus sheath at 14 days after transplanting (DAT), while they were positively related to N uptake of the shoot, leaf lamina, and stem plus sheath at the middle and later stages. N use efficiency and N uptake differed according to urea type and N management. PASP-urea increased N accumulation of the shoot by improving N uptake of the leaf lamina and stem plus sheath from DAT 27, contributing to the significant improvement in NRE, NAE, and PFP. PASP-urea with optimized N management markedly improved the N uptake of each organ at the middle and latter stages, leading to increased final N uptake of the shoot, NRE, NAE, and PFP. Using PASP-urea with ONM method is a suitable way for improving both N accumulation and N use efficiency.     

Optimizing nitrogen management strategy under wheat straw incorporation for higher rice production and nitrogen use efficiency

Nitrogen (N) application plays an important role in rice production. Limited attention has already been paid to optimizing N fertilizer management strategy for higher grain yield and nitrogen use efficiency (NUE) of rice with crop residue incorporation. Field experiments were conducted with the objective to determine the response of several N application methods to rice production and to evaluate their NUE. Three N fertilizer application methods, i.e., local farmers' N fertilizer practice (FNP), modified farmers' N fertilizer practice (MNP), and increased the amount of N fertilizer practice (INP), were adopted with zero N application as control (CK). The results showed that, compared with that under FNP, grain yield was significantly higher under MFP, owing to signficantly enhanced total spikelets as a result of more panicles per unit area. Relative to FNP, MNP markedly increased nitrogen agronomic efficiency (AE_N), nitrogen recovery efficiency (RE_N), nitrogen physiological efficiency (PE_N) and nitrogen partial factor productivity (PFP_N), but AE_N, PE_N and PFP_N of INP were significantly lower. Further analysis showed that the number of tiller, leaf area index, aboveground biomass, SPAD value, plant N content and N uptake at the early vegetative stage were improved significantly under MNP compared to those under FNP, contributing to higher total aboveground biomass and total N uptake.     

Water use efficiency in a soybean field: influence of plant water stress

Measurements were made in 1980 over a fully-developed soybean (Glycine max (L.) Merrill) canopy at Mead, Nebraska to determine how crop water status influences photosynthesis, evapotranspiration and water use efficiency. Water use efficiency was calculated in terms of the CO₂—water flux ratio (CWFR). Micrometeorological techniques were used to measure the exchange rates of CO₂ and water vapor above the crop canopy. Crop water status was evaluated by reference to volumetric soil moisture (θ_v), stomatal resistance (r_s), and leaf water potential (ψ) measurements.Stomatal resistance (r_s) was independent of ψ when the latter was greater than ?1.1 MPa. r_s increased sharply as ψ dropped below this threshold. Canopy CO₂ exchange (F_c) decreased logarithmically with increasing r_s under strong irradiance. Although F_c was found to be strongly correlated with r_s, the influence of low values of ψ and of high air temperature cannot be discounted since these factors affect the enzymatic reactions associated with photosynthesis. Stomatal closure also reduced evapotranspiration and influenced the partitioning of net radiation.Under strong irradiance the CO₂ water flux ratio (CWFR) decreased with increasing stomatal resistance. This observation is at variance with predictions of certain early ‘resistance’ models, but substantiates predictions of some recent models in which leaf energy balance considerations are incorporated.     

Changes in the agrochemical properties of dark gray soil in the Western Ukrainian forest-steppe under the effect of long-term agricultural use

The changes in the properties of dark gray forest soil in the Ukrainian Western Forest-Steppe under the effect of long-term agricultural use in a grain-row crop rotation without fertilization and with the application of mineral and organomineral complex fertilizers have been studied. The changes in the morphological properties of the soil, the reaction of the soil solution, the total and exchangeable acidities, the total exchangeable bases, the degree of base saturation, and the content and reserve of organic carbon over a 50-year-long period of plowing have been studied using different methods. It has been found that the acidification of the upper layer was intensified and the content of organic matter and the degree of base saturation decreased during the period studied (1961–2010). The effect of the management practice on the evolution and dynamics of the soil degradation has been studied. It has been shown that the cultivation of soils without fertilization primarily resulted in a decrease in the humus content; the application of mineral fertilizers increased the acidity of the soils.     

Effects of cloudiness change on net ecosystem exchange, light use efficiency, and water use efficiency in typical ecosystems of China

As a weather element, clouds can affect CO₂ exchange between terrestrial ecosystems and the atmosphere by altering environmental conditions, such as solar radiation received on the ground surface, temperature, and moisture. Based on the flux data measured at five typical ecosystems of China during mid-growing season (June-August) from 2003 to 2006, we analyzed the responses of net ecosystem exchange of carbon dioxide (NEE), light use efficiency (LUE, defined as Gross ecosystem photosynthesis (GEP)/Photosynthetically active radiation (PAR)), and water use efficiency (WUE, defined as GEP/Evapotranspiration (ET)) to the changes in cloudiness. The five ecological sites included Changbaishan temperate mixed forest (CBS), Dinghushan subtropical evergreen broad-leaved forest (DHS), Xishuangbanna tropical rainforest (XSBN), Inner Mongolia semi-arid Leymus chinensis steppe (NMG), and Haibei alpine frigid Potentilla fruticosa shrub (HB). Our analyses show that cloudy sky conditions with cloud index (k_t) values between 0.4 and 0.6 increased NEE, LUE, and WUE of the ecosystems at CBS, DHS, NMG and HB from June to August. The LUE of tropical rainforest at XSBN was higher under cloudy than under clear sky conditions, but NEE and WUE did not decrease significantly under clear sky conditions from June to August. The increase in GEP with increasing diffuse radiation received by ecosystems under cloudy skies was the main reason that caused the increases in LUE and net carbon uptake in forest ecosystem at CBS, DHS, and alpine shrub ecosystem at HB, compared with clear skies. Moreover, for the ecosystem at CBS, DHS, and HB, when sky condition became from clear to cloudy, GEP increased and ET decreased with decreasing VPD, leading to the increase in WUE and NEE under cloudy sky conditions. The decrease in R_e with decreasing temperature and increase in GEP with decreasing VPD under cloudy skies led to the increase in LUE, WUE, and net carbon uptake of semi-arid steppe at NMG, compared to clear skies. These different responses among the five ecosystems are attributable to the differences in canopy characteristics and water conditions. From June to August, the peaks of the k_t frequency distribution in temperate ecosystems (e.g., CBS, NMG, and HB) were larger than 0.5, but they were smaller than 0.4 in subtropical/tropical forest ecosystems (e.g., DHS and XSBN). These results suggest that the pattern of cloudiness during the years from 2003 to 2006 in the five ecosystems was not the best condition for their net carbon uptake. This study highlights the importance of cloudiness factor in the prediction of net carbon absorption in the Asia monsoon region under climate change.     

Evaluation of common bean genotypes for phosphorus use efficiency

A greenhouse experiment was conducted to evaluate phosphorus (P)‐use efficiency of 10 promising genotypes of common bean (Phaseoius vulgaris L.) with short and normal growth duration. The genotypes were grown on an Oxisol at 25 mg P kg^‐1 (low P) and 150 mg P kg^‐1 (high P) of soil. Shoot and root dry weight, root length, P concentration in the shoot, and P uptake in the shoot were significantly (P<0.01) affected by soil P concentration and genotype. However, P level did not effect root length and genotype had no effect on root dry weight. On the basis of P‐use efficiency (mg dry weight of shoot/mg P accumulated in the shoot) genotypes were classified as efficient and responsive (ER), efficient and nonresponsive (ENR), nonefficient and responsive (NER), and nonefficient and nonresponsive (NENR). From a practical point of view, genotypes which produce a lot of dry matter in a soil with a low P level, and respond well to added P are the most desirable because they are able to express their high yield potential in a wide range of P environments. Novo Jalo and Pérola genotypes fall into this group. Genotypes Irai, Jalo Precoce and L93300166 fall into the ENR group. Genotypes Carioca, Rosinha G‐2, and Xamengo were classified NER, whereas, genotypes L93300176 and Diamante Negro were classified as NENR. There were no differences between short and normal growth duration genotypes in P‐use efficiency.     

Biochemical aspects of nitrogen use efficiency: An overview

Crop productivity relies heavily on nitrogen (N) fertilization. N is an essential macronutrient limiting the growth and development of plants in agriculture. Both organic and inorganic forms of N are metabolized in plants; nitrate and ammonia are common forms of inorganic N that can be metabolized in all plants. In the last 40 years the amount of synthetic N applied to crops has risen dramatically, resulting in significant increases in yield but with considerable impacts on the environment. Production and application of N fertilizers consume huge amounts of energy, and excess is detrimental to the environment. A requirement for crops that require decreased N fertilizer levels has been recognized in the call for a ‘Second Green Revolution’ and research in the field of nitrogen-use efficiency (NUE) has continued to grow. Nitrogen-use efficiency is inherently a complex trait, as each step-including N uptake, translocation, assimilation, and remobilization-is governed by multiple interacting genetic and environmental factors. The limiting factors in plant metabolism for maximizing NUE are different at high and low N supplies, indicating great potential for improving the NUE of present cultivars. Decreasing environmental losses and increasing the productivity of crop-acquired N requires the coordination of carbohydrate and N metabolism to give high yields. This has prompted a search to identify genes that improve the NUE of crop plants, with candidate NUE genes existing in pathways relating to N uptake, assimilation, amino acid biosynthesis, carbon (C)/N storage and metabolism, signaling and regulation of N metabolism and translocation, remobilization and senescence. In this review, we present the over view of N metabolism, relation of C/N metabolism and future prospects of improving NUE in crops using various complementary approaches.     

Interactive effects of sowing date and nitrogen fertilizer on water and nitrogen use efficiency in millet cultivars under drought stress

Abstract

This study was conducted to investigate the effects of two irrigation regimes (55 and 85% of soil available water depletion) and two nitrogen levels (0 and 112.5?kg ha^?1) on yield as well as water and nitrogen use efficiencies of two millet cultivars (namely, Bastan and Pishahang) planted at two sowing dates during 2015 and 2016. Growth parameters and nitrogen use of the millet cultivars were found affected by drought, nitrogen level, and sowing date as well as their interactions. Nitrogen application was found to improve not only nitrogen uptake, chlorophyll content, and irrigation water use efficiency (IWUE) but also grain and biological yields; more positive effects were, however, observed under the control irrigation regime. Nevertheless, nitrogen uptake (NUpE), utilization (NUtE), and use (NUE) efficiencies decreased as a result of nitrogen application. The increases in grain yield (16 versus 7%) and IWUEg (17 versus 6%) due to nitrogen application were more pronounced in the drought-tolerant Bastan cultivar than in the drought-sensitive Pishahang. However, nitrogen application decreased NUpE in both cultivars. Although water stress increased soil N residual with all the sowing dates, the increase was greater with the early ones. The results of the experiment suggest that the application of higher nitrogen levels is not the proper strategy for compensating for the reduced yield under drought conditions. Rather, late sowing dates, due to the lower drought effects associated, might be the proper alternative for achieving higher yields as well as improved IWUE and NUE in areas plagued with water shortage.     

Carbon isotope discrimination and water use efficiency in Iranian diploid,tetraploid and hexaploid wheats grown under well-watered conditions

Carbon isotope discrimination (Δ) has been proposed as physiological criterion to select C₃ crops for yield and water use efficiency. The relationships between carbon isotope discrimination (Δ), water use efficiency for grain and biomass production (WUE_G and WUE_B, respectively) and plant and leaf traits were examined in 20 Iranian wheat genotypes including einkorn wheat (Triticum monococcum L. subsp. monococcum) accessions, durum wheat (T. turgidum L. subsp. durum (Desf.) Husn.) landraces and bread wheat (T. aestivum L. subsp. aestivum) landraces and improved cultivars, grown in pots under well-watered conditions. Carbon isotope discrimination was higher in diploid than in hexaploid and tetraploid wheats and was negatively associated with grain yield across species as well as within bread wheat. It was also positively correlated to stomatal frequency. The highest WUE_G and grain yield were noted in bread wheat and the lowest in einkorn wheat. Einkorn and bread wheat had higher WUE_B and biomass than durum wheat. WUE_G and WUE_B were significantly negatively associated to Δ across species as well as within bread and durum wheat. The variation for WUE_G was mainly driven by the variation for harvest index across species and by the variation for Δ within species. The quantity of water extracted by the crop, that was closely correlated to root mass, poorly influenced WUE_G. Environmental conditions and genetic variation for water use efficiency related traits appear to highly determine the relationships between WUE_G and its different components (water consumed, transpiration efficiency and carbon partitioning).     

Red chicories as potent scavengers of highly reactive radicals: a study on their phenolic composition and peroxyl radical trapping capacity and efficiency

Eight varieties of Cichorium genus vegetables (five heavily red colored, one red spotted, and two fully green) were investigated for their phenolic content (by HPLC and UV-vis spectrophotometry) and for their antioxidant activity. In particular, the capacity (that is, the amount of trapped peroxyl radicals) and the efficiency (that is, the amount of antioxidant necessary to halve the steady-state concentration of peroxyl radicals) were measured. All of the studied chicories are characterized by the presence of a large amount of hydroxybenzoic and hydroxycinnamic acids, whereas the red color is due to cyanidin glycosides. The presence of these phenolics in red chicories confers to them an exceptionally high peroxyl radical scavenging activity in terms of both capacity and efficiency, particularly in their early stage of growth, and makes this popular and low-cost foods comparable or superior to many foods having well-known antioxidant properties such as red wine, blueberry, and tomato.     

Use of Cs to estimate tillage- and water-induced soil redistribution rates on agricultural land under different use and management in central-south Chile

The purpose of this research was to evaluate the applicability of conventional ¹³⁷Cs sampling and a simplified approach, for estimating medium-term tillage- and water-induced soil erosion and sedimentation rates on agricultural land in Chile. For this purpose, four study sites under contrasting land use and management were selected in central-south Chile. First, a conventional ¹³⁷Cs approach, based on grid sampling was applied, adapting a mass balance conversion model incorporating soil movement by tillage to the site specific conditions of the study region. Secondly, using the same conversion model, the feasibility of estimating soil redistribution rates from measurements of ¹³⁷Cs inventories based on composite soil samples taken along contour lines was also tested at all four sites. The redistribution rates associated with tillage and water and the total rates estimated using both methods correlated strongly at all four sites. The conventional method provides more detailed information concerning the redistribution processes operating over the landscape. The simplified method is suitable for assessing soil loss and sediment accumulation in areas exhibiting simple topography and almost similar slopes along the contour lines. Under these conditions, this method permits faster estimation of soil redistribution rates, providing the possibility of estimating soil redistribution rates over larger areas in a shorter time. In order to optimise the costs and benefits of the methods, the sampling and inventory quantification strategy must be selected according to the resolution of the required information, and the scale and complexity of the landscape relief. Higher tillage- and water-induced erosion rates were observed in the annually ploughed cropland sites than in the semi-permanent grassland sites. Subsistence managed crop and grassland sites also show greater erosion effects than the commercially managed sites. The ¹³⁷Cs methods used permit discrimination between redistribution rates observed on agricultural land under different land use and management. The ¹³⁷Cs technique must be seen as an efficient method for estimating medium-term soil redistribution rates, and for planning soil conservation and sustainable agricultural production under the climatic conditions and the soil type of the region of Chile investigated.     

Dynamics of bulk composition of gray forest soil under agricultural treatment

It is shown that the bulk composition of the plow layer of gray forest easy-loamy soil in forests under agricultural treatment is enriched with phosphorus, calcium, and molybdenum. For these elements, no differences are found between different types of treatment. The trends for zinc and copper have opposite results under different types of treatment.     

Influence of continuous plastic film mulching on yield, water use efficiency and soil properties of rice fields under non-flooding condition

Five field experiments were conducted to study the effects of continuous plastic film mulching on rice yield, water use efficiency and soil properties on different soils with great environmental variabilities in Zhejiang Province, China, under non-flooding condition. The experiment started in 2001 at five sites and ended in 2003 with one rice crop annually. Three treatments included plastic film mulching with no flooding (PM), no plastic film mulching and no flooding (UM), and traditional flooding management (TF). Soil samples were collected after the third year of the experimentation and were analyzed for soil properties. PM increased soil temperature, accelerated decomposition of organic carbon and root growth, there was a slight but statistically insignificant trend of decline in soil bulk density. PM produced the similar rice grain yield as TF at two sites, significantly higher grain yield (5.8% and 20.0% higher) at other two sites, but significantly lower (34.3% lower) yield at one site where no irrigation water was applied and rainfall was the sole water source for rice growth. PM increased water use efficiency by 69.6–106.0% and irrigation water use efficiency by 273.7–519.6%. Compared to TF, PM decreased soil organic matter content by 8.3–24.5%, soil total N by 5.2–22.0%, and available K by 9.6–50.4% at all sites. PM treatment also reduced soil available N by 8.5–26.5% at four sites. Soil total P content in PM treatments reduced by 13.5–27.8% at three sites, and increased by 6.6–8.2% at other two sites. However, PM increased soil available P by 20.9–64.7% at all sites. Systematic cluster analysis indicated the PM treatment distinctively clustered from the other treatment. These results suggested PM could gain higher yield under appropriate water condition and PM may change soil nutrient cycle.     

The yields,agronomic, and nitrogen use efficiency traits of wheat cultivars in north China under N-sufficient and -deficient conditions

In this study, the yields, yield components, agronomic, and nitrogen use efficiency (NUE) traits of the eighty-four winter wheat cultivars were investigated under nitrogen (N)-sufficient and -deficient conditions. Dramatic variations were observed in the yield and agronomic traits among the cultivars. Based on absolute yields under the N treatments, the cultivars were categorized into N efficiency groups of high, close high, medium, and low, in which the high efficiency group cultivars generally exhibited improved agronomic traits under these contrasting N-supply conditions. Additionally, the wheat cultivars were classified into various N response groups, including toleration, relative toleration, sensitive, and most sensitive based on the ratios of yield under N deficiency to that under N sufficiency. Regression correlation analyses revealed that straw biomass, total biomass, grain N amount, and straw N amount were significantly correlated with yield, suggesting that these traits can be acted as indices in evaluating yield potentials in wheat.