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1.
ABSTRACT

Lucerne or alfalfa (Medicago sativa L.) is grown as a forage crop on many livestock farms. In calcareous soils in eastern Turkey, lucerne production requires phosphorus (P) additions as the soils are naturally P deficient. Phosphorus sorption isotherms were used to estimate P fertilizer needs for lucerne grown for two years in a 3-cut system on a calcareous P deficient Aridisol in eastern Anatolia, Erzurum province, Turkey. Annual P applications ranged from 0–1200 kg P ha?1. The Langmuir two-surface adsorption equation was used to derive the maximum P sorption capacity of unamended soil and to determine soil solution P, maximum buffer capacity (MBC), equilibrium buffer capacity (EBC), and P saturation at the optimum economic P rate (OEPR) for dry matter (DM) production. Soils were tested for Olson P at the onset of the study and after two years of P applications. In both years, tissue was analyzed for P content at flowering prior to first cutting. The OEPR (2-year average) was 754 kg P ha?1 yr?1 corresponding with a soil solution P concentration of 0.30 mg L?1, a DM yield of 8725 kg DM ha?1, and $528 ha?1 annual profit. The P content of leaves at flowering increased linearly with P application beyond 100 kg P ha?1 and was 3.2 g kg?1 P at the OEPR. The unfertilized soil had an EBC, MBC, P saturation, and Xmax of 3304 mL g?1, 3401 mL g?1, 6%, and 1086 mL g?1, respectively, whereas two years of fertilization to the OEPR decreased EBC and MBC to 358 mL g?1 and 540 mL g?1, and increased P saturation and Olsen P to 56% and 32 mg kg?1, respectively. These results suggest a P saturation >50% or Olsen P >30 mg kg?1 are needed to maintain an optimum soil solution concentration of 0.30 mg L?1 in this calcareous Aridisol. Similar studies with different soils and initial soil test P levels are needed to conclude if these critical soil test values can be applied across the region.  相似文献   

2.
Annual potassium (K) balances have been calculated over a 40‐year period for five field experiments located on varying parent materials (from loamy sand to clay) in south and central Sweden. Each experiment consisted of a number of K fertilizer regimes and was divided into two crop rotations, mixed arable/livestock (I) and arable only (II). Annual calculations were based on data for K inputs through manure and fertilizer, and outputs in crop removal. Plots receiving no K fertilizer showed negative K balances which ranged from 30 to 65 kg ha?1 year?1 in rotation I, compared with 10–26 kg ha?1 year?1 for rotation II. On sandy loam and clay soils, the K yield of nil K plots (rotation I) increased significantly with time during the experimental period indicating increasing release of K from soil minerals, uptake from deeper soil horizons and/or depletion of exchangeable soil K (Kex). Significant depletion of Kex in the topsoil was only found in the loamy sand indicating a K supply from internal sources in the sandy loam and clay soils. On silty clay and clay soils, a grass/clover ley K concentration of ～2% (dry weight) was maintained during the 40‐year study period on the nil K plots, but on the sandy loam, loam and loamy sand, herbage concentrations were generally less than 2% K.  相似文献   

3.
Abstract

This study was conducted to investigate the effect of time and rate of phosphorus (P) addition on phosphorus availability and phosphorus buffer coefficient in some calcareous soils. Phosphorus was added to the samples at rates of 0, 50, 100, 200, 400, 600 and 800 mg P kg?1 soil. The samples were incubated for 0.041, 1, 7, 14, 21, 30, 60 and 90 days at constant temperature and moisture. Extractable phosphorus was determined after the incubation. The results showed a sharp decrease in available P within 1 h after P addition. There was a linear relation between added P and extractable P in all soils. The buffer coefficients of soils were estimated by Olsen P for above incubation periods. Generally the buffer coefficient decreased with increasing time of incubation. The results indicated that inputs of between 23 – 59 mg kg?1 are required to raise Olsen P by 10 mg kg?1 in these calcareous soils, which assuming 2500 t soil ha?1, gives a required input of 58 – 148 kg P ha?1.  相似文献   

4.
Over-fertilization has caused significant phosphorus(P) accumulation in Chinese greenhouse vegetable production(GVP) soils. This study, for the first time, quantified profile P accumulation directly from soil P measurements, as well as subsoil P immobilization, in three alkaline coarse-textured GVP soil profiles with 5(S5), 15(S15), and 30(S30) years of cultivation in Tongshan, Southeast China. For each profile, soil samples were collected at depths of 0–10(topsoil), 10–20, 20–40, 40–60, 60–80, and 80–100 cm. Phosphorus accumulation was estimated from the difference in P contents between topsoil and parent material(60–100 cm subsoil). Phosphorus mobility was assessed from measurements of water-soluble P concentration(PSol). Finally, P sorption isotherms were produced using a batch sorption experiment and fitted using a modified Langmuir model. High total P contents of 1 980(S5), 3 190(S15), and 2 330(S30) mg kg~(-1) were measured in the topsoils versus lower total P content of approximately 600 mg kg~(-1) in the 80–100 cm subsoils. Likewise, topsoil PSol values were very high, varying from 6.4 to 17.0 mg L~(-1). The estimated annual P accumulations in the topsoils were 397(S5), 212(S15), and 78(S30) kg ha~(-1) year~(-1). Sorption isotherms demonstrated the dominance of P desorption in highly P-saturated topsoils, whereas the amount of adsorbed P increased in the 80–100 cm subsoils with slightly larger P adsorption capacity. The total P adsorption capacity of the 80–100 cm subsoils at a solution P concentration of0.5 mg L~(-1) was 15.7(S5), 8.7(S15), and 6.5(S30) kg ha~(-1), demonstrating that subsoils were unable to secure P concentrations in leaching water below 0.5 mg L~(-1) because of their insufficient P-binding capacity.  相似文献   

5.
Reactive (RP) and organic phosphorus (OP) losses from grazed paddocks were determined on a volcanic soil during 2004 and 2005. Paddocks were grazed by Holstein Friesian steers (3.5 steers ha?1) and received N (67.5 kg ha?1) and P fertilizer (30 kg P ha?1). Total losses ranged between 4 and 15 g P ha?1 year?1 and were greatly affected by incidental P losses associated with spring P fertilizer application. Reactive P constituted 90% of the total losses on average. Due to the high water infiltration capacity of the soil, run‐off was <1% of total drainage, therefore, phosphorus losses in run‐off were small.  相似文献   

6.
Nitrogen balances and total N and C accumulation in soil were studied in reseeded grazed grassland swards receiving different fertilizer N inputs (100–500 kg N ha?1 year?1) from March 1989 to February 1999, at an experimental site in Northern Ireland. Soil N and C accumulated linearly at rates of 102–152 kg N ha?1 year?1 and 1125–1454 kg C ha?1 year?1, respectively, in the top 15 cm soil during the 10 year period. Fertilizer N had a highly significant effect on the rate of N and C accumulation. In the sward receiving 500 kg fertilizer N ha?1 year?1 the input (wet deposition + fertilizer N applied) minus output (drainflow + animal product) averaged 417 kg N ha?1 year?1. Total N accumulation in the top 15 cm of soil was 152 kg N ha?1 year?1. The predicted range in NH3 emission from this sward was 36–95 kg N ha?1 year?1. Evidence suggested that the remaining large imbalance was either caused by denitrification and/or other unknown loss processes. In the sward receiving 100 kg fertilizer N ha?1 year?1, it was apparent that N accumulation in the top 15 cm soil was greater than the input minus output balance, even before allowing for gaseous emissions. This suggested that there was an additional input source, possibly resulting from a redistribution of N from lower down the soil profile. This is an important factor to take into account in constructing N balances, as not all the N accumulating in the top 15 cm soil may be directly caused by N input. N redistribution within the soil profile would exacerbate the N deficit in budget studies.  相似文献   

7.
In grassland farming, especially on coarse‐textured soils, K can be a critical element. On these soils, the actual K management as well as fertilizer history to a large extent determine the leaching of K. The effects of four fertilizer regimes on the nutrient balances and leaching of K from grassland grown on a sandy soil were investigated. The swards differed in the source and level of N input and K fertilizer: no fertilizer N + 166 kg K ha?1 year?1 (Control), 320 kg inorganic N ha?1 + 300 kg K ha?1 year?1 (MIN 320), 320 kg N + 425 kg K ha?1 year?1 in form of cattle slurry (SLR 320) and a grass–clover sward + 166 kg K ha?1 year?1 (WCL 0) without any inorganic N input. In a second experimental phase, cores from these swards were used in a mini‐lysimeter study on the fate of K from urine patches. On cut grassland after 6 years K input minus removal in herbage resulted in average K surpluses per year of 47, 39, 56 and 159 kg K ha?1 for the Control, MIN 320, WCL 0 and SLR 320, respectively. Related leaching losses per year averaged 7.5, 5, 15 and 25 kg K ha?1. Losses of urinary‐K through leaching were 2.2–4.5 and 5.7–8.4% of the K supplied in summer and autumn applications, respectively. Plant and soil were the major sinks for K from fertilizer or urine. High levels of exchangeable K in the soil and/or large and late fertilizer or urine applications stimulated leaching of K.  相似文献   

8.
ABSTRACT

In recent decades, rare earths and rare-earth containing fertilizers along with nitrogen (N) and phosphorus (P) fertilizers have been used by agriculturists to improve crop yield and quality. The interaction between rare earths and N has been explained in soils, yet little is known of the effect of rare earths on P nutrition of field-grown crops. When maize plants entered the early stem-elongation stage, a rare earth-containing fertilizer (lanthanum (La) and cerium (Ce) as major rare earths) was applied to the soil with irrigation water. Ten days after application of rare earths, there was no significant dose-dependent accumulation of P in the roots and shoots, with one exception where P concentrations increased in the roots at a dosage of 100 kg rare earths ha? 1. However, at maturity, the application of rare earths at less than 10 kg ha? 1 significantly improved P uptake by field-grown maize and P transport to the grain. The application of rare earths at less than 10 kg ha? 1 increased crop yield. Other studies have shown that at rates less than 10 kg rare earths ha? 1, there was no accumulation of heavy metals and rare earths in the grain, and that the present mean application rate of rare earths (< 0.23 kg ha? 1 year? 1) currently applied in China was unlikely to affect the safety of grains in arable soils. Together, these field studies can give a scientific understanding of benefits and risks when utilizing rare earths in agriculture, and of the interaction between rare earths and P nutrition in field-grown crops.  相似文献   

9.
This paper describes the accumulation of uranium in soils from superphosphate applied annually to arable and grassland soils. Rates of application of superphosphate were equivalent to about 33kg P and 15 gU ha?1 year?1 in three experiments at Rothamsted and to about 37 kg P and 16g U ha ?1 year ?1 in one experiment in New Zealand. Most of the uranium (about 1300 g U ha ?1) applied in superphosphate to the clay loam soil at Rothamsted since 1889 was retained, like P, in the plough layer of arable soils or was adsorbed by the organic surface layers of soils under permanent grassland. Uranium applied in superphosphate to grassland in New Zealand since 1954 (about 330 g U ha?1) was also concentrated in the surface layers of the soil.  相似文献   

10.
Fertilizer phosphorus (P) is generally added to agricultural soils to meet the needs of crop production. In this study, the crop yield and soil Olsen P were measured every year (5–18 years) at 16 winter wheat (Triticum aestivum L.) –maize (Zea mays L.) crop rotation sites in cinnamon soil (Luvisols in FAO system). The mean agronomic critical value of Olsen P for maize was 14.2 mg kg?1 and for winter wheat was 14.4 mg kg?1 when using the Liner-plateau and Mitscherlich models. The change in soil Olsen P was positively linearly correlated with the P budget (P < 0.01), and an increase of 4.70 mg kg?1 in soil Olsen P for each 100 kg ha?1 of P budget in the 0–20 cm soil layer. A model of P fertilizer recommendation rate that integrated values of the change in soil Olsen P in response to P budget and the agronomic critical value of Olsen P was used, in order to adjust current levels of soil Olsen P to the agronomic critical value at the experimental sites over the next 5 years, P fertilizer application rate should be in the range of 0–87.5 kg P ha?1.  相似文献   

11.
The effects of 25 years of annual applications of P fertilizer on the accumulation and migration of soil Olsen‐P, and the effects of soil residual P on crop yields by withholding P application for the following 5 years, were evaluated in a subtropical region. Annual application of P fertilizer for 25 years to crops in summer (groundnut), winter (wheat, mustard or rapeseed) or in both seasons raised the Olsen‐P status of the plough layer (0–15 cm) from initially very low (12 kg P ha?1) to medium (18 kg P ha?1) and very high levels (40–59 kg P ha?1), depending on the amount of P surplus (amount of fertilizer applied in excess of removal by crops) (r = 0.86, P ≥ 0.01). However, only 4–9% of the applied P fertilizer accumulated as Olsen‐P to a depth of 15 cm (an increase of 2 mg kg?1per 100 kg ha?1 surplus P) in the sandy loam soil. In the following 5 years, the raising of 10 crops without P fertilizer applications decreased the accumulated Olsen‐P by only 20–30% depending upon the amount of accumulated P and crop requirements. After 29 years, 45–256 kg of residual P fertilizer had accumulated as Olsen‐P ha?1 in the uppermost 150 cm with 43–58% below 60 cm depth; this indicates enormous movement of applied P to deeper layers in this coarse textured soil with low P retention capacity for nutrients. Groundnut was more efficient in utilizing residual P than rapeseed; however, for both crops the yield advantage of residual P could be compensated for by fresh P applications. These results demonstrated little agronomic advantage above approximately 20 mg kg?1 Olsen‐P build‐up and suggested that further elevation of soil P status would only increase the risk of environmental problems associated with the loss of P from agricultural soils in this region.  相似文献   

12.
Phosphorus (P) inputs (wet deposition and fertilizer P) and outputs (animal product and drainflow) were studied on reseeded grazed grassland swards receiving different nitrogen (N) inputs (100–500 kg N ha?1 year?1) for 10 years (March 1989–February 1999), at an experimental site in Northern Ireland. All plots received the same maintenance application of P fertilizer (8.5 kg P ha?1 year?1) to meet grass requirements, to minimize the P surplus and to quantify the impact on P losses to land drainage water. The annual flow weighted mean total P concentrations in drainflow ranged from 187 to 273 μg P litre?1 and were well above the concentrations believed to trigger eutrophication. Annual total P lost to drainage water ranged from 0.28 to 1.73 kg P ha?1, but was unaffected by N input. As the average annual P balance was zero, there was no significant change in total P in the top 15 cm of soil. However, there was a highly significant redistribution of P to the soil surface from the 10–15 cm depth, possibly as a result of root acquisition and earthworm activity. Total P in the top 5 cm of soil increased from 0.85 g kg?1 to 1.04 g kg?1, over the 10 years of the study, despite there being no net P input. This P accumulation in the top few cm of soil is likely to exacerbate P losses in overland flow and make improvements in water quality difficult to achieve.  相似文献   

13.
To establish a national inventory of soil organic carbon (SOC) stocks and their change over time, soil was sampled in 1986, 1997 and 2009 in a Danish nation‐wide 7‐km grid and analysed for SOC content. The average SOC stock in 0–100‐cm depth soil was 142 t C ha?1, with 63, 41 and 38 t C ha?1 in the 0–25, 25–50 and 50–100 cm depths, respectively. Changes at 0–25 cm were small. During 1986–97, SOC in the 25–50‐cm layer increased in sandy soils while SOC decreased in loam soils. In the subsequent period (1997–2009), most soils showed significant losses of SOC. From 1986 to 2009, SOC at 0–100 cm decreased in loam soils and tended to increase in sandy soils. This trend is ascribed to dairy farms with grass leys being abundant on sandy soils while cereal cropping dominates on loamy soils. A statistical model including soil type, land use and management was applied separately to 0–25, 25–50 and 50–100 cm depths to pinpoint drivers for SOC change. In the 0–25 cm layer, grass leys added 0.95 t C ha?1 year?1 and autumn‐sown crops with straw incorporation added 0.40 t C ha?1 year?1. Cattle manure added 0.21 t C ha?1 year?1. Most interestingly, grass leys contributed 0.58 t C ha?1 year?1 at 25–50 cm, confirming that inventories based only on top‐soils are incomplete. We found no significant effects in 50–100 cm. Our study indicates a small annual loss of 0.2 t C ha?1 from the 0–100 cm soil layer between 1986 and 2009.  相似文献   

14.
Data from a 49-year-long organic–mineral fertilization field experiment with a potato–maize–maize–wheat–wheat crop rotation were used to analyse the impact of different fertilizer variations on yield ability, soil organic carbon content (SOC), N and C balances, as well as on some characteristic energy balance parameters. Among the treatments, the fertilization variant with 87 kg ha?1 year?1 N proved to be economically optimal (94% of the maximum). Approximately 40 years after initiation of the experiment, supposed steady-state SOC content has been reached, with a value of 0.81% in the upper soil layer of the unfertilized control plot. Farmyard manure (FYM) treatments resulted in 10% higher SOC content compared with equivalent NPK fertilizer doses. The best C balances were obtained with exclusive mineral fertilization variants (?3.8 and ?3.7 t ha?1 year?1, respectively). N uptake in the unfertilized control plot suggested an airborne N input of 48 kg ha?1 year?1. The optimum fertilizer variant (70 t ha?1 FYM-equivalent NPK) proved favourable with a view to energy. The energy gain by exclusive FYM treatments was lower than with sole NPK fertilization. Best energy intensity values were obtained with lower mineral fertilization and FYM variants. The order of energy conversion according to the different crops was maize, wheat and potato.  相似文献   

15.
The productivity of sorghum, an important staple food crops in semi-arid tropics of the world, is low due to scarcity of moisture and poor soil fertility. Response of crops to phosphorus (P) application in these soils is erratic and tricky, which depends upon the available P status in soils, distribution of rainfall, adsorption and desorption capacity of soil, and overall P sink created by crop depending upon its vigor. Delineation of optimum P level for higher productivity and to avoid wastage of precious P fertilizer thus becomes inevitable. Hence, an experiment was conducted at Hayathnagar Research Farm of Central Research Institute for Dryland Agriculture, Hyderabad to i) study the external (relative grain yields, agronomic efficiency, harvest index) and internal response (fertilizer P use efficiency, P uptake harvest index) indicators of sorghum to various levels of P application, ii) development of prediction functions to arrive at optimum P dose and iii) P use - removal balance for grain sorghum for these rainfed semi-arid tropical Alfisols. Results of the study indicated that P application to sorghum in these Alfisol soils beyond 23 kg ha?1 might not be much economical and desirable. It was observed that the maximum grain yield of 87% could be achieved at a leaf P concentration of 0.39% at boot leaf or flag leaf stage and 0.30% at 50% flowering stage. The prediction functions were developed to understand the quantitative relationship between external and internal response indicators. The zero P balance (neither depletion nor excessive build up) obtained at 20 kg ha?1 level (per se near 23 kg P ha?1) indicates that this level is sufficient for sorghum crop to perform with an agronomic efficiency of 19.42 kg grain kg?1 P. The findings of this study would help in efficient use of P fertilizer for achieving desirable yield levels and will in turn reduce the expenditure on P fertilizers that are mostly imported by India and majority of other developing countries.  相似文献   

16.
This study investigated phosphorus (P) dynamics and kinetics in calcareous soil under inorganic, organic, and integrated (inorganic+organic) fertilizer systems during two growing seasons of maize in two soil depths (0–0.15 and 0.15–0.30 m). A field experiment was conducted with 150, 300, and 400 kg ha?1 triple superphosphate (TSP), 7.5 and 15.0 ton ha?1 (on dry matter basis) farmyard manure (FYM), and integrated systems. In order to analyze Olsen P, soil samples were collected in 30-day-intervals after planting. The results showed that at the end of the two growing seasons of maize, the lowest magnitudes of Olsen P0–0.15 m were 6.0, 6.8, 7.4, and 7.6 mg kg?1 for the control, 7.5 FYM, 15 FYM, and 150 TSP, respectively. The highest magnitudes of Olsen P0–0.15 m were 12.4, 11.5, 11.4, and 11.1 mg kg?1 for 300 TSP+15 FYM, 400 TSP+7.5 FYM, 400 TSP+15 FYM, and 300 TSP+7.5 FYM, respectively. The same trends were observed for Olsen P0.15–0.30 m. Heterogeneous diffusion model demonstrated that Elovich equation could best describe the experimental data (mean; R2 = 0.98, SE = 0.29). The highest P supply rates (PSR) were 4.73, 3.91, and 3.86 mg kg?1day?1 (days after application) for 400 TSP, 400 TSP+15 FYM, and 300 TSP, respectively. The models of P supply capacity of soil could estimate P supply of soil under different fertilizer systems (R2 = 0.84–0.95). The present study improved the understanding of the capacity and rate of P supply by considering P uptake by grain maize. Fertilizer recommendations depend on the accessibility of fertilizer types suggested to help choose the best fertilizer systems.  相似文献   

17.
Management effects on forms of phosphorus in soil and leaching losses   总被引：12，自引：0，他引：12  
We should know the effects of soil use and management on the contents and forms of soil phosphorus (P) and the resulting potential for leaching losses of P to prevent eutrophication of surface water. We determined P test values, amounts of sequentially extracted forms of P, P sorption capacities and degrees of P saturation in 20 differently treated soils and compared these data with leaching losses in lysimeters. One-way analyses of variance indicated that most fractions of P were significantly influenced by soil texture, land use (grassland, arable or fallow or reafforestation), mineral fertilization and intensity of soil management. Generally, sandy soils under grass and given large amounts of P fertilizer contained the most labile P and showed the largest P test values. Fallow and reafforestation led to smallest labile P fractions and relative increases of P extractable by H2SO4 and residual P. Arable soils with organic and mineral P fertilization given to crop rotations had the largest amounts of total P, labile P fractions and P test values. The mean annual concentrations of P in the lysimeter leachates varied from 0 to 0.81 mg l–1 (mean 0.16 mg l–1) and the corresponding leaching losses of P from < 0.01 to 3.2 kg ha–1 year–1 (mean 0.3 kg P ha–1 year–1). These two sets of data were correlated and a significant exponential function (R2 = 0.676) described this relation. Different soil textures, land uses and management practices resulted in similar values for P leaching losses as those for the amounts of labile P fractions. Surprisingly, larger rates of mineral P fertilizer did not necessarily result in greater leaching losses. The contents of P extracted by NaHCO3 and acid oxalate and the degrees of P saturation were positively correlated with the concentrations of P in leachates and leaching losses. As the P sorption capacity and degree of P saturation predicted leaching losses of P better than did routinely determined soil P tests, they possibly can be developed as novel P tests that meet the requirements of plant nutrition and of water protection.  相似文献   

18.
Impact of integrated nutrient and crop residue management on crop productivity, phosphorus (P) uptake and apparent P balances was investigated in a 5-year field experiment on two calcareous soils, i.e., Awagat (coarse loamy) and Shahpur (fine silty) in cotton-wheat sequence. Minimum mean P uptake (kg ha?1) by cotton with Farmers’ Fertilizer Use (FFU) treatment was 8.89 in Awagat and 11.54 in Shahpur soil. Corresponding maximum mean P uptake was 15.30 and 17.01 kg ha?1 with Integrated Nutrient Management (INM), respectively. Nutrient treatments effect on P uptake by wheat was similar to cotton. Phosphorus uptake was further enhanced by crop residue recycling. Phosphorus uptake trend by cotton was negative under FFU without residue recycling and was positive with residue recycling. While P uptake trends were positive under all other treatments. INM yielded positive apparent P balances (kg ha?1) of 56–306 in Awagat and 24–288 in Shahpur soil.  相似文献   

19.
ABSTRACT

Phosphorus (P) nutrition of the rice-wheat (RW) systems of the Indo-Gangetic Plain of South Asia has become important due to the alternate flooding and drying cycles of this crop rotation. Field experiments on the RW cropping sequence were conducted at three locations of Bangladesh on three soil types. Two fertilizer doses—farmers' practice (FP) and soil-test based (STB), containing recommended amounts of P, nitrogen (N), potassium (K), and other nutrients—were compared with mungbean or maize as a third crop. The objective of the experiments was to detect P deficiency, if any, in rice, wheat, mungbean, and maize, and to compare the FP and STB doses of fertilizers in rice-wheat-mungbean and rice-wheat-maize sequences under two mungbean management practices (residue removed or retained) and one maize management practice (residue removed) in terms of P nutrition of those crops and annual system-level P removal and apparent P balance in the soil. The apparent P balance was negative with the FP dose (?1 to ?9 kg ha?1 for mungbean sequences at Joydebpur and Nashipur) and there was soil P accumulation under both the STB dose (9–49 kg ha?1) and zero N control (13–50 kg ha?1) across sites. The effect of maize or mungbean as the pre-rice crop on the apparent P balance of various RW sequences was not significant. Phosphorus deficiency occurred at all sites in wheat and maize, and at Ishwordi in rice, suggesting that P fertilizer recommendations need to be revised for RW systems in Bangladesh. The results also suggest that long-term monitoring for P concentration, uptake, and balance would be necessary for improving not only the productivity and sustainability of this system but also the fertilizer P-use efficiency.  相似文献   

20.
Abstract

To assess their impacts on net global warming, total greenhouse gas emissions (mainly CO2, N2O and CH4) from agricultural production in arable land cropping systems in the Tokachi region of Hokkaido, Japan, were estimated using life cycle inventory (LCI) analysis. The LCI data included CO2 emissions from on-farm and off-farm fossil fuel consumption, soil CO2 emissions induced by the decomposition of soil organic matter, direct and indirect N2O emissions from arable lands and CH4 uptake by soils, which were then aggregated in CO2-equivalents. Under plow-based conventional tillage (CT) cropping systems for winter wheat, sugar beet, adzuki bean, potato and cabbage, on-farm CO2 emissions from fuel-consuming operations such as tractor-based field operations, truck transportation and mechanical grain drying ranged from 0.424 Mg CO2 ha?1 year?1 for adzuki bean to 0.826 Mg CO2 ha?1 year?1 for winter wheat. Off-farm CO2 emissions resulting from the use of agricultural materials such as chemical fertilizers, biocides (pesticides and herbicides) and agricultural machines were estimated by input–output tables to range from 0.800 Mg CO2 ha?1 year?1 for winter wheat to 1.724 Mg CO2 ha?1 year?1 for sugar beet. Direct N2O emissions previously measured in an Andosol field of this region showed a positive correlation with N fertilizer application rates. These emissions, expressed in CO2-equivalents, ranged from 0.041 Mg CO2 ha?1 year?1 for potato to 0.382 Mg CO2 ha?1 year?1 for cabbage. Indirect N2O emissions resulting from N leaching and surface runoff were estimated to range from 0.069 Mg CO2 ha?1 year?1 for adzuki bean to 0.381 Mg CO2 ha?1 year?1 for cabbage. The rates of CH4 removal from the atmosphere by soil uptake were equivalent to only 0.020–0.042 Mg CO2 ha?1 year?1. From the difference in the total soil C pools (0–20 cm depth) between 1981 and 2001, annual CO2 emissions from the CT and reduced tillage (RT) soils were estimated to be 4.91 and 3.81 Mg CO2 ha?1 year?1, respectively. In total, CO2-equivalent greenhouse gas emissions under CT cropping systems in the Tokachi region of Hokkaido amounted to 6.97, 7.62, 6.44, 6.64 and 7.49 Mg CO2 ha?1 year?1 for winter wheat, sugar beet, adzuki bean, potato and cabbage production, respectively. Overall, soil-derived CO2 emissions accounted for a large proportion (64–76%) of the total greenhouse gas emissions. This illustrates that soil management practices that enhance C sequestration in soil may be an effective means to mitigate large greenhouse gas emissions from arable land cropping systems such as those in the Tokachi region of northern Japan. Under RT cropping systems, plowing after harvesting was omitted, and total greenhouse gas emissions from winter wheat, sugar beet and adzuki bean could be reduced by 18%, 4% and 18%, respectively, mainly as a result of a lower soil organic matter decomposition rate in the RT soil and a saving on the fuels used for plowing.  相似文献   

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