Nutrient Cycling in Agroecosystems 

About: Nutrient Cycling in Agroecosystems is an academic journal published by Springer Science+Business Media. The journal publishes majorly in the area(s): Fertilizer & Soil water. It has an ISSN identifier of 1385-1314. Over the lifetime, 2079 publications have been published receiving 92798 citations.

Influence of lime, fertilizer and manure applications on soil organic matter content and soil physical conditions: A review

Abstract: The effects of lime, fertilizer and manure applications on soil organic matter status and soil physical properties are of importance to agricultural sustainability. Their effects are complex and many interactions can occur. In the short-term, liming can result in dispersion of clay colloids and formation of surface crusts. As pH is increased the surface negative charge on clay colloids increases and repulsive forces between particles dominate. However, at higher lime rates, Ca2+ concentrations and ionic strength in soil solution increase causing compression of the electrical double layer and renewed flocculation. When present in sufficient quantities, both lime and hydroxy-Al polymers formed by precipitation of exchangeable Al, can act as cementing agents bonding soil particles together and improving soil structure. Liming often causes a temporary flush of soil microbial activity but the effect of this on soil aggregation is unclear. It is suggested that, in the long-term, liming will increase crop yields, organic matter returns, soil organic matter content and thus soil aggregation. There is a need to study these relationships on existing long-term liming trials. Fertilizers are applied to soils in order to maintain or improve crop yields. In the long-term, increased crop yields and organic matter returns with regular fertilizer applications result in a higher soil organic matter content and biological activity being attained than where no fertilizers are applied. As a result, long-term fertilizer applications have been reported, in a number of cases, to cause increases in water stable aggregation, porosity, infiltration capacity and hydraulic conductivity and decreases in bulk density. Fertilizer additions can also have physico-chemical effects which influence soil aggregation. Phosphatic fertilizers and phosphoric acid can favour aggregation by the formation of Al or Ca phosphate binding agents whilst where fertilizer NH4 + accumulates in the soil at high concentrations, dispersion of clay colloids can be favoured. Additions of organic manures result in increased soil organic matter content. Many reports have shown that this results in increased water holding capacity, porosity, infiltration capacity, hydraulic conductivity and water stable aggregation and decreased bulk density and surface crusting. Problems associated with large applications of manure include dispersion caused by accumulated K+, Na+ and NH4 + in the soil and production of water-repellant substances by decomposer fungi.

Closing the global N2O budget: nitrous oxide emissions through the agricultural nitrogen cycle

Abstract: In 1995 a working group was assembled at the request of OECD/IPCC/IEA to revise the methodology for N2O from agriculture for the National Greenhouse Gas Inventories Methodology. The basics of the methodology developed to calculate annual country level nitrous oxide (N2O) emissions from agricultural soils is presented herein. Three sources of N2O are distinguished in the new methodology: (i) direct emissions from agricultural soils, (ii) emissions from animal production, and (iii) N2O emissions indirectly induced by agricultural activities. The methodology is a simple approach which requires only input data that are available from FAO databases. The methodology attempts to relate N2O emissions to the agricultural nitrogen (N) cycle and to systems into which N is transported once it leaves agricultural systems. These estimates are made with the realization that increased utilization of crop nutrients, including N, will be required to meet rapidly growing needs for food and fiber production in our immediate future. Anthropogenic N input into agricultural systems include N from synthetic fertilizer, animal wastes, increased biological N-fixation, cultivation of mineral and organic soils through enhanced organic matter mineralization, and mineralization of crop residue returned to the field. Nitrous oxide may be emitted directly to the atmosphere in agricultural fields, animal confinements or pastoral systems or be transported from agricultural systems into ground and surface waters through surface runoff. Nitrate leaching and runoff and food consumption by humans and introduction into sewage systems transport the N ultimately into surface water (rivers and oceans) where additional N2O is produced. Ammonia and oxides of N (NOx) are also emitted from agricultural systems and may be transported off-site and serve to fertilize other systems which leads to enhanced production of N2O. Eventually, all N that moves through the soil system will be either terminally sequestered in buried sediments or denitrified in aquatic systems. We estimated global N2O–N emissions for the year 1989, using midpoint emission factors from our methodology and the FAO data for 1989. Direct emissions from agricultural soils totaled 2.1 Tg N, direct emissions from animal production totaled 2.1 Tg N and indirect emissions resulting from agricultural N input into the atmosphere and aquatic systems totaled 2.1 Tg N2O–N for an annual total of 6.3 Tg N2O–N. The N2O input to the atmosphere from agricultural production as a whole has apparently been previously underestimated. These new estimates suggest that the missing N2O sources discussed in earlier IPCC reports is likely a biogenic (agricultural) one.

Nitrate leaching in temperate agroecosystems: sources, factors and mitigating strategies

Abstract: Nitrate (NO3 −) leaching from agriculturalproduction systems is blamed for the rising concentrations ofNO3 − in ground- and surface-waters around the world.This paper reviews the evidence of NO3 − leachinglosses from various land use systems, including cut grassland, grazed pastures,arable cropping, mixed cropping with pasture leys, organic farming,horticultural systems, and forest ecosystems. Soil, climatic and managementfactors which affect NO3 − leaching are discussed.Nitrate leaching occurs when there is an accumulation ofNO3 − in the soil profile that coincides with or isfollowed by a period of high drainage. Therefore, excessive nitrogen (N)fertilizer or waste effluent application rates or N applications at the wrongtime (e.g. late autumn) of the year, ploughing pasture leys early in the autumn,or long periods of fallow ground, can all potentially lead to highNO3 − leaching losses. N returns in animal urine havea major impact on NO3 − leaching in grazed pastures.Of the land use systems considered in this paper, the potential for causingNO3 − leaching typically follow the order: forest< cut grassland < grazed pastures, arable cropping < ploughing ofpasture < market gardens. A range ofmanagement options to mitigate NO3 − leaching isdescribed, including reducing N application rates, synchronizing N supply toplant demand, use of cover crops, better timing of ploughing pasture leys,improved stock management, precision farming, and regulatory measures. This isfollowed by a discussion of future research needs to improve our ability topredict and mitigate NO3 − leaching.

N2O and NO emission from agricultural fields and soils under natural vegetation: summarizing available measurement data and modeling of global annual emissions

Abstract: The number of published N2O and NO emissions measurements is increasing steadily, providing additional information about driving factors of these emissions and allowing an improvement of statistical N-emission models. We summarized information from 1008 N2O and 189 NO emission measurements for agricultural fields, and 207 N2O and 210 NO measurements for soils under natural vegetation. The factors that significantly influence agricultural N2O emissions were N application rate, crop type, fertilizer type, soil organic C content, soil pH and texture, and those for NO emissions include N application rate, soil N content and climate. Compared to an earlier analysis the 20% increase in the number of N2O measurements for agriculture did not yield more insight or reduced uncertainty, because the representation of environmental and management conditions in agro-ecosystems did not improve, while for NO emissions the additional measurements in agricultural systems did yield a considerable improvement. N2O emissions from soils under natural vegetation are significantly influenced by vegetation type, soil organic C content, soil pH, bulk density and drainage, while vegetation type and soil C content are major factors for NO emissions. Statistical models of these factors were used to calculate global annual emissions from fertilized cropland (3.3 Tg N2O-N and 1.4 Tg NO-N) and grassland (0.8 Tg N2O-N and 0.4 Tg NO-N). Global emissions were not calculated for soils under natural vegetation due to lack of data for many vegetation types.

Direct emission of nitrous oxide from agricultural soils

Abstract: This analysis is based on published measurements of nitrous oxide (N2O) emission from fertilized and unfertilized fields. Data was selected in order to evaluate the importance of factors that regulate N2O production, including soil conditions, type of crop, nitrogen (N) fertilizer type and soil and crop management. Reported N2O losses from anhydrous ammonia and organic N fertilizers or combinations of organic and synthetic N fertilizers are higher than those for other types of N fertilizer. However, the range of management and environmental conditions represented by the data set is inadequate for use in estimating emission factors for each fertilizer type. The data are appropriate for estimating the order of magnitude of emissions. The longer the period over which measurements are made, the higher the fertilizer-induced emission. Therefore, a simple equation to relate the total annual direct N2O−N emission (E) from fertilized fields to the N fertilizer applied (F), was based on the measurements covering periods of one year: E=1+1.25×F, with E and F in kg N ha-1 yr-1. This relationship is independent of the type of fertilizer. Although the above regression equation includes considerable uncertainty, it may be appropriate for global estimates.