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1.
Abstract

An outdoor pot experiment was conducted using wheat plants (Triticum aestivum L. cv. Lotti). Each pot was filled with the upper layer of either a Cambic arenosol (soil A) or a Dystric cambisol (soil B) removed from the correspondent lysimeter where a two‐year wheat experiment (1993–1995) had been carried out with an equivalent experimental design as in the present study. The main objectives of this research were (1) to study the effects of increasing applications (5, 15, and 25 t ha‐1) of solid phase from pig slurry (SP) on wheat yield and tissue elemental composition and (2) to investigate the risk of contamination of drainage water by leaching of phosphorus (P) and mineral nitrogen (Nmin) as a result of those applications to the soil. The control consisted of a basic dressing of NPK fertilizer. Results from the study showed that grain production was lower in the 5 and 15 t ha‐1 SP treatments compared to the control in soil A probably due to a potassium (K) deficiency. Increasing application rates of SP significantly enhanced P and Nmin leaching losses in both soils. Finally on soil A high rates of SP amendments led to the contamination of water with P.  相似文献   

2.
The beneficial effect of sewage sludge in crop production has been demonstrated, but there is concern regarding its contribution to nitrate (NO3) leaching. The objectives of this study were to compare nitrogen (N) rates of sewage sludge and ammonium nitrate (NH4NO3) on soil profile (0–180 cm), inorganic N [ammonium nitrate (NH4‐N) and nitrate nitrogen (NO3‐N)] accumulation, yield, and N uptake in winter wheat (Triticum aestivum L.). One field experiment was established in 1993 that evaluated six N rates (0 to 540 kg·ha‐1·yr‐1) as dry anaerobically digested sewage sludge and ammonium nitrate. Lime application in 1993 (4.48 Mg ha‐1) with 540 kg N ha‐1·yr‐1 was also evaluated. A laboratory incubation study was included to simulate N mineralization from sewage sludge applied at rates of 45, 180, and 540 kg N ha‐1·yr‐1. Treatments did not affect surface soil (0–30 cm) pH, organic carbon (C), and total N following the first (1994) and second (1995) harvest. Soil profile inorganic N accumulation increased when ≥270 kg N ha‐1 was applied as ammonium nitrate. Less soil profile inorganic N accumulation was detected when lime was applied. In general, wheat yields and N uptake increased linearly with applied N as sewage sludge, while wheat yields and N uptake peaked at 270 kg N ha‐1 when N was applied as ammonium nitrate. Lime did not affect yields or N uptake. Fertilizer N immobilization was expected to be high at this site where wheat was produced for the first time in over 10 years (previously in native bermudagrass). Estimated N use efficiency using sewage sludge in grain production was 20% (average of two harvests) compared to ammonium nitrate. Estimated plant N recovery was 17% for sewage sludge and 27% for ammonium nitrate.  相似文献   

3.
Abstract. In dairy farming systems the risk of nitrate leaching is increased by mixed rotations (pasture/arable) and the use of organic manure. We investigated the effect of four organic farming systems with different livestock densities and different types of organic manure on crop yields, nitrate leaching and N balance in an organic dairy/crop rotation (barley–grass-clover–grass-clover–barley/pea–winter wheat–fodder beet) from 1994 to 1998. Nitrate concentrations in soil water extracted by ceramic suction cups ranged from below 1 mg NO3-N l?1 in 1st year grass-clover to 20–50 mg NO3-N l?1 in the winter following barley/pea and winter wheat. Peaks of high nitrate concentrations were observed in 2nd year grass-clover, probably due to urination by grazing cattle. Nitrate leaching was affected by climatic conditions (drainage volume), livestock density and time since ploughing in of grass-clover. No difference in nitrate leaching was observed between the use of slurry alone and farmyard manure from deep litter housing in combination with slurry. Increasing the total-N input to the rotation by 40 kg N ha?1 year?1 (from 0.9 to 1.4 livestock units ha?1) only increased leaching by 6 kg NO3-N ha?1. Nitrate leaching was highest in the second winter (after winter wheat) following ploughing in of the grass-clover (61 kg NO3-N ha?1). Leaching losses were lowest in 1st year grass-clover (20 kg NO3-N ha?1). Averaged over the four years, nitrate concentration in drainage water was 57 mg l?1. Minimizing leaching losses requires improved utilization of organic N accumulated in grazed grass-clover pastures. The N balance for the crop rotation as a whole indicated that accumulation of N in soil organic matter in the fields of these systems was small.  相似文献   

4.
Leaching of nutrients in soil can change the surface and groundwater quality. The present study aimed at investigating the effects of raw and ammonium (NH4+)-enriched zeolite on nitrogen leaching and wheat yields in sandy loam and clay loam soils. The treatments were one level of nitrogen; Z0: (100 kg (N) ha?1) as urea, two levels of raw zeolite; Z1:(0.5 g kg?1 + 100 kg ha?1) and Z2: (1 g kg?1 + 100 kg ha?1), and two levels of NH4+-enriched zeolite; Z3: (0.5 g kg?1 + 80 kg ha?1) and Z4: (1 g kg?1 + 60 kg ha?1). Wheat grains were sown in pots and, after each irrigation event, the leachates were collected and their nitrate (NO3?) and NH4+ contents were determined. The grain yield and the total N in plants were measured after four months of wheat growth. The results indicated that the amounts of NH4+ and NO3? leached from the sandy loam soil were more than those from the clay loam soil in all irrigation events. The maximum and minimum concentrations of nitrogen in the drainage water for both soils were observed at control and NH4+-zeolite treatments, respectively. Total N in the plants grown in the sandy loam was higher compared to plants grown in clay loam soil. Also, nitrogen uptake by plants in control and NH4+-zeolite was higher than that of raw-zeolite treatments. The decrease in the amount of N leaching in the presence of NH4+-zeolite caused more N availability for plants and increased the efficiency of nitrogen fertilizers and the plants yield.  相似文献   

5.
A two‐year lysimeter experiment was conducted using winter wheat plants on two texturally contrasting soils (soil A and soil B). The main objective of this study was to evaluate the influence of increasing doses (5, 10, 15, 20, and 251 ha‐1) of solid phase from pig slurry (SP) on soil extractable copper (Cu), zinc (Zn), iron (Fe), and manganese (Mn) and on wheat micronutrients composition and uptake. As the control, a basic dressing of NPK fertilizer was applied. Results showed that increasing additions of SP significantly enhanced extractable Cu, Zn, Fe, and Mn content on the topsoil for both soils tested. In addition, a significant increase was detected for extractable Cu, Zn, and Mn content with increasing application rates of SP for subsoil A, but no significant differences were detected for subsoil B. A significant increase in the contents of Fe, Mn, and Zn in the plants as well as total uptakes were observed from increasing doses of SP. Copper content in the plants was not significantly affected. Finally, a strong pH effect was exerted in the Mn and Zn uptake by the plants.  相似文献   

6.
Abstract

To determine the relationships between microbial biomass nitrogen (N), nitrate–nitrogen leaching (NO3-N leaching) and N uptake by plants, a field experiment and a soil column experiment were conducted. In the field experiment, microbial biomass N, 0.5 mol L?1 K2SO4 extractable N (extractable N), NO3-N leaching and N uptake by corn were monitored in sawdust compost (SDC: 20 Mg ha?1 containing 158 kg N ha?1 of total N [approximately 50% is easily decomposable organic N]), chemical fertilizer (CF) and no fertilizer (NF) treatments from May 2000 to September 2002. In the soil column experiment, microbial biomass N, extractable N and NO3-N leaching were monitored in soil treated with SDC (20 Mg ha?1) + rice straw (RS) at five different application rates (0, 2.5, 5, 7.5 and 10 Mg ha?1 containing 0, 15, 29, 44 and 59 kg N ha?1) and in soil treated with CF in 2001. Nitrogen was applied as (NH4)2SO4 at rates of 220 kg N ha?1 for SDC and SDC + RS treatments and at a rate of 300 kg N ha?1 for the CF treatment in both experiments. In the field experiment, microbial biomass N in the SDC treatment increased to 147 kg N ha?1 at 7 days after treatment (DAT) and was maintained at 60–70 kg N ha?1 after 30 days. Conversely, microbial biomass N in the CF treatment did not increase significantly. Extractable N in the surface soil increased immediately after treatment, but was found at lower levels in the SDC treatment compared to the CF treatment until 7 DAT. A small amount of NO3-N leaching was observed until 21 DAT and increased markedly from 27 to 42 DAT in the SDC and CF treatments. Cumulative NO3-N leaching in the CF treatment was 146 kg N ha?1, which was equal to half of the applied N, but only 53 kg N ha?1 in the SDC treatment. In contrast, there was no significant difference between N uptake by corn in the SDC and CF treatments. In the soil column experiment, microbial biomass N in the SDC + RS treatment at 7 DAT increased with increased RS application. Conversely, extractable N at 7 DAT and cumulative NO3-N leaching until 42 DAT decreased with increased RS application. In both experiments, microbial biomass N was negatively correlated with extractable N at 7 DAT and cumulative NO3-N leaching until 42 DAT, and extractable N was positively correlated with cumulative NO3-N leaching. We concluded that microbial biomass N formation in the surface soil decreased extractable N and, consequently, contributed to decreasing NO3-N leaching without impacting negatively on N uptake by plants.  相似文献   

7.
A field study was conducted in the sub-humid tropical region of India to examine the effect of different nitrogen (N) management strategies on nitrate leaching, nitrous oxide (N2O) emission and N use efficiency in aerobic rice. Treatments were: control (no N), 120 kg N ha?1 applied as prilled urea (PU) in conventional method, 120 kg N ha?1 applied as neem coated urea (NCU) in conventional method, N applied as PU on the basis of leaf colour chart (LCC) reading, N applied as NCU on the basis of LCC reading, and 120 kg N ha?1 applied as PU and farm yard manure (FYM) in 1:1 ratio. Results showed that 3.4–16.1 kg NO3-N ha?1 was leached below 45 cm depth and 0.61–1.12 kg N2O-N ha?1 was emitted from aerobic rice during the growing season. NCU when applied conventionally reduced nitrate-nitrogen (NO3-N) leaching and N2O emission by 18.6% and 21.4%, respectively However when applied on the basis of LCC reading NCU reduced NO3-N leaching by 39.8% as compared to PU applied in conventional method. NCU when applied on the basis of LCC reading synchronized N supply with demand and reduced N loss, which resulted in higher yield and N use efficiency.  相似文献   

8.
Nitrate (NO3?) can contribute to surface water eutrophication and is deemed harmful to human health if present at high concentrations in the drinking water. In grazed grassland, most of the NO3?‐N leaching occurs from animal urine‐N returns. The objective of this study was to determine the effectiveness of a nitrification inhibitor, dicyandiamide (DCD), in decreasing NO3? leaching in three different soils from different regions of New Zealand under two different rainfall conditions (1260 mm and 2145 mm p.a.), and explore the relationships between NO3?‐N leaching loss and ammonia oxidizing bacteria (AOB) and ammonia oxidizing archaea (AOA). The DCD nitrification inhibitor was found to be highly effective in decreasing NO3?‐N leaching losses from all three soils under both rainfall conditions. Total NO3?‐N leaching losses from the urine patch areas were decreased from 67.7–457.0 kg NO3?‐N/ha to 29.7–257.4 kg NO3?‐N/ha by the DCD treatment, giving an average decrease of 59%. The total NO3?‐N leaching losses were not significantly affected by the two different rainfall treatments. The total NO3?‐N leaching loss was significantly related to the amoA gene copy numbers of the AOB DNA and to nitrification rate in the soil but not to that of the AOA. These results suggest that the DCD nitrification inhibitor is highly effective in decreasing NO3? leaching under these different soil and rainfall conditions and that the amount of NO3?‐N leached is mainly related to the growth of the AOB population in the nitrogen rich urine patch soils of grazed grassland.  相似文献   

9.
Approximately 40% of New Zealand's land mass is fertilized grassland with entirely non‐native plants, but currently there is substantially increased interest in restoration of native plants into contemporary agricultural matrices. Native vegetation is adapted to more acid and less fertile soils and their establishment and growth may be constrained by nutrient spillover from agricultural land. We investigated plant–soil interactions of native N‐fixing and early successional non N‐fixing plants in soils with variable fertility. The effects of soil amendments of urea (100 and 300 kg N ha?1), lime (6000 kg CaCO3 ha?1), and superphosphate (470 kg ha?1) and combinations of these treatments were evaluated in a glasshouse pot trial. Plant growth, soil pH, soil mineral N, Olsen P and nodule nitrogenase activity in N‐fixing plants were measured. Urea amendments to soil were not inhibitory to the growth of native N‐fixing plants at lower N application rates; two species responded positively to combinations of N, P and lime. Phosphate enrichment enhanced nodulation in N‐fixers, but nitrogen inhibited nodulation, reduced soil pH and provided higher nitrate concentrations in soil. The contribution of mineral N to soil from the 1‐year old N‐fixing plants was small, in amounts extrapolated to be 10–14 kg ha?1 y?1. Urea, applied both alone and in conjunction with other amendments, enhanced the growth of the non N‐fixing species, which exploited mineral N more efficiently; without N, application of lime and P had little effect or was detrimental. The results showed native N‐fixing plants can be embedded in agroecology systems without significant risk of further increasing soil fertility or enhancing nitrate leaching.  相似文献   

10.
Nitrate leaching from intensively and extensively grazed grassland measured with suction cup samplers and sampling of soil mineral‐N I Influence of pasture management Leaching of nitrate (NO3—) from two differently managed cattle pastures was determined over four winters between 1993 and 1997 using ceramic suction cup samplers (with min. 34 cups ha—1); additionally, vertical soil mineral‐N content in 0—0.9 m (Nmin) was measured at the beginning and end of two winters (with min. 70 different sample cores ha—1). The experimental site in the highlands north‐east of Cologne, Germany, is characterized by high annual precipitation (av. 1,362 mm between 1993 and 1996). An intensive continuous grazing management (1.3 ha, fertilized with 250 kg N ha—1 yr—1, average stocking density 4.9 LU ha—1, = [I]) was tested against an extensive continuous grazing system (2.2 ha, av. 2.9 LU ha—1; no N‐fertilizer but an estimated proportion of Trifolium repens up to 15 % of total dry matter in the final year, = [E]). The results can be summarized as follows: (1) Mean leaching losses of NO3‐N, estimated from suction cup sampling and balance of drainage volume, were 85 kg NO3‐N ha—1 [I] and 15 kg NO3‐N ha—1 [E] during three wet winters with drainage volumes between 399 and 890 mm; in a dry winter with 105 mm calculated percolation, nitrate leaching decreased by a factor of 5 for both grazing treatments. (2) Although the amount of mineral N in soil (Nmin) sampled in late autumn showed differences between intensive and extensive grazing, the Nmin method permits no certain indication of the risk of NO3 leaching. For example, during the winter period 1994/95 a reduction of mineral N in the soil (0—0.9 m) in both grazing treatments was found (—33 [I] / —8 [E] kg NO3‐N ha—1 and —26 [I] / —21 [E] kg NH4‐N ha—1) whereas during the winter 1996/97 an increase in almost all mean mineral N values occurred (+10 [I] / +2 [E] kg NO3‐N ha—1 and +10 [I] / —10 [E] kg NH4‐N ha—1). (3) In spite of the differences between both methods, the experiment shows that NO3‐N leaching under extensive grazing could be reduced almost to levels close to those under mown grassland.  相似文献   

11.
Abstract. The repeated application of pig slurry to agricultural soils may result in an accumulation of salts and a risk of aquifer pollution due to nitrate leaching and salinization. Under Mediterranean conditions, a field experiment on a sandy loam soil (Typic Xerofluvent) was performed with maize (Zea mays) in 1998, 1999 and 2001 to study the effects of applying optimal (P1) and excessive rates (P3) of pig slurry on soil salinization, nitrate leaching and groundwater pollution. The rate of pig slurry was established considering the optimal N rate for maize in this soil (170, 162 and 176 kg N ha?1 for 1998, 1999 and 2001, respectively). Pig slurry treatments were compared to an optimal N rate supplied as urea (U) and a control treatment without N fertilizer (P0). The composition of the slurries showed great variability between years. Mean NO3? leaching losses from 1998 to 2001 were 329, 215, 173 and 78 kg N ha?1 for P3, P1, U and P0 treatments, respectively. The amount of total dissolved salts (TDS) added to the soil in slurry application between 1998 and 2001 was 2019 kg TDS ha?1 for the P1 treatment and 6058 kg TDS ha?1 for the P3 treatment. As a consequence, the electrical conductivity (EC) of the slurry‐treated soils was greater than that of the control soil. The EC correlated significantly with the sodium concentration of the soil solution. Over the entire experimental period, 2653, 2202 and 2110 kg Na ha?1 entered the aquifer from the P3, P1 and P0 treatments, respectively. The P3 treatment did not significantly increase grain production in 1999 and 2001 compared with that achieved with the optimal N rate treatment (P1). This behaviour shows the importance of establishing application guidelines for pig slurry that will reduce the risk of soil and groundwater pollution.  相似文献   

12.
Compost amendment to agricultural soils has been reported to reduce disease incidence, conserve soil moisture, control weeds, or improve soil fertility. Application rate and placement of compost largely depends on the proposed beneficial effects and the rate may vary from 25 to 250 Mg ha?1 (N content up to 4 percent). Application of high rates of compost with high N or P levels may result in excessive leaching of nitrate, ammonium, and phosphate into the groundwater. Leaching could be a serious concern on the east coast of Florida with its inherent high annual rainfall, sandy soils and shallow water table. In this study, five composts (sugarcane filtercake, biosolids, and mixtures of municipal solid wastes and biosolids) were applied on the surface of an Oldsmar sand soil (in 7.5 cm diameter leaching columns) at 100 Mg ha?1 rate and leached with deionized water (300 ml day?1, for five days; equivalent to 34 cm rainfall). The concentrations of NO3-N, NH4-N, and PO4-P in leachate reached as high as 246, 29, and 7 mg L?1, respectively. The amount of N and P leached accounted for 3.3-15.8 percent of total N and 0.2-2.8 percent of total P in the compost. The leaching peaks of NO3-N occurred following the application of only 300-400 ml water (equivalent to 6.8-9.1 cm rainfall).  相似文献   

13.
Abstract

Inhibition of nitrification in soil results in a decreased ratio of nitrate‐nitrogen (NO3‐N) to ammonium‐nitrogen (NH4‐N). If the conditions for NO3‐N loss by leaching or denitrification exist, nitrification inhibitors should increase concentrations of total inorganic soil nitrogen (N) (TISN) (NH4‐N + NO3‐N). This can then result in plants taking up more N and developing more crop yield or biomass. This study examined whether inhibition of nitrification by dicyandiamide (DCD) would result in increased concentrations of TISN under field conditions. The effects of DCD on soil N were evaluated in hyperthermic sandy soils planted to potato (Solanum tuberosum L., cv. Atlantic). Treatments were factorial combinations of N as ammonium nitrate (NH4NO3) at 67, 134, and 202 kg N ha‐1 and DCD at 0, 5.6, and 11.2 kg DCD ha‐1. Soil NH4‐N, NO3‐N, and TISN concentrations were determined for up to five potato growth stages at two locations for two years for a total of 16 determinations (cases), i.e., four were not determined. The N form ratio [NO3‐N/(NH4‐N + NO3‐N] x 100 was decreased in 10 of 16 cases, indicating that nitrification was inhibited by DCD. With two of these 10 cases, TISN concentration increased, but with four others, TISN concentration decreased with at least one N rate. With four of these 10 cases, inhibition of nitrification had no effect on TISN concentration. Under the conditions of these field studies, DCD inhibited nitrification more often than not. Inhibition of nitrification was, however, more likely to reduce TISN concentration than to increase it. This may have been due to DCD effects on immobization of applied NH4‐N.  相似文献   

14.
Nitrogen (N) surpluses from fertilizer application can cause major environmental harm including pollution of surface water, groundwater, and air. To assess such negative externalities, N balances are a complex but useful tool to predict surpluses and to measure effects of nutrient optimization strategies in agriculture. The Yaqui Valley in north‐western Mexico is representative for thousands of square kilometres of intensive, irrigated wheat production under arid conditions worldwide and has been targeted for conservation agriculture in recent years. For these cropping systems, detailed N balances are scarce and often incomplete. To help fill this knowledge gap, data from a long‐term experiment were collected in 2013/14 on a Vertisol to examine the impact of three tillage‐straw management practices (CTB: conventionally tilled beds; PB‐straw: permanent raised beds with residue retention; PB‐burn: permanent raised beds with residue burning) on N dynamics. Tillage had significant effects on soil NO3‐N, NH4‐N, and total N contents across the cropping period. Soil total N content was at all sampling depths lowest in CTB. Soil NO3‐N in the 0–90 cm profile was highest in PB‐burn over the cropping period and ranged from 77 kg ha?1 in the bed before pre‐planting fertilizer application up to 269 kg ha?1 in the furrow after the second fertilizer application. Annual simple N balances were +59 kg N ha?1 in CTB, +39 kg N ha–1 in PB‐straw, and +46 kg N ha?1 in PB‐burn. Residual mineral soil N was significantly affected by tillage‐straw management and lowest for PB‐straw (+205 kg N ha?1) and highest for CTB, and for PB‐burn (+283 kg N ha?1 each) in the 0–90 cm soil profile. Soil NO3‐N moved out of the effective wheat root zone, as indicated by the high residual NO3‐N content at 30–90 cm depth, which is an important pathway of N leaching. Quantifiable N losses through leaching and volatilization averaged 100 kg N ha?1. Our findings suggest that there is potential for substantial reductions in N inputs in all tillage‐straw systems to decrease N losses and to reduce mineral residual soil N, but care should be taken to avoid reducing grain protein content, which in PB straw was already below the quality standard. A knowledge transfer of the European “Nmin” concept is advisable in this region to regulate N fertilizer over‐application.  相似文献   

15.
中国太湖地区稻麦轮作农田硝态氮动态与氮素平衡   总被引：1，自引：0，他引：1  
Nitrate-nitrogen (NO 3--N) dynamics and nitrogen (N) budgets in rice (Oryza sativa L.)-wheat (Triticum aestivum L.) rotations in the Taihu Lake region of China were studied to compare the effects of N fertilizer management over a two-year period. The experiment included four N rates for rice and wheat, respectively: N1 (125 and 94 kg N ha-1 ), N2 (225 and 169 kg N ha-1 ), N3 (325 and 244 kg N ha-1 ), and N0 (0 kg N ha-1 ). The results showed that an overlying water layer during the rice growing seasons contributed to moderate concentrations of NO 3--N in sampled waters and the concentrations of NO 3--N only showed a rising trend during the field drying stage. The NO 3--N concentrations in leachates during the wheat seasons were much higher than those during the rice seasons, particularly in the wheat seedling stage. In the wheat seedling stage, the NO 3--N concentrations of leachates were significantly higher in N treatments than in N0 treatment and increased with increasing N rates. As the NO 3--N content (below 2 mg N L-1 ) at a depth of 80 cm during the rice-wheat rotations did not respond to the applied N rates, the high levels of NO 3--N in the groundwater of paddy fields might not be directly related to NO 3--N leaching. Crop growth trends were closely related to variations of NO 3--N in leachates. A reduction in N application rate, especially in the earlier stages of crop growth, and synchronization of the peak of N uptake by the crop with N fertilizer application are key measures to reduce N loss. Above-ground biomass for rice and wheat increased significantly with increasing N rate, but there was no significant difference between N2 and N3. Increasing N rates to the levels greater than N2 not only decreased N use efficiency, but also significantly increased N loss. After two cycles of rice-wheat rotations, the apparent N losses of N1, N2 and N3 amounted to 234, 366 and 579 kg N ha-1 , respectively. With an increase of N rate from N0 to N3, the percentage of N uptake in total N inputs decreased from 63.9% to 46.9%. The apparent N losses during the rice seasons were higher than those during the wheat seasons and were related to precipitation; therefore, the application of fertilizer should take into account climate conditions and avoid application before heavy rainfall.  相似文献   

16.
Dairy manure (DM) rates of [0 (DM0), 30 (DM30)), 60 (DM60) Mg ha?1] and three nitrogen (N) rates [0 (N0), 125 (N125), 250 (N250) kg ha?1] were tested in a sandy clay loam, to evaluate their effects on growth and yield of wheat crop (Triticum aestivum L.), residual nitrate nitrogen (NO3-N) and phosphorus (P) concentrations in the surface soil, and selected soil physical measurements [saturated hydraulic conductivity (Ksat), and bulk density (BD)]. Increasing N and DM rates gave higher wheat yields, increased concentrations of residual NO3-N and P in the surface soil and improved Ksat and BD. Highest grain yield of 3.8 Mg ha?1 (70.3% more than the control) was observed in DM60 × N250 treatment. Residual accumulation of N-NO3 and P in the surface soil at high N and/or DM application rates suggests the need to carefully manage N and DM inputs on farm fields to avoid environmental contamination.  相似文献   

17.
Abstract

Plant growth in saline soils is regulated by the availability of nitrogen (N). High soil nitrate (NO3)‐N can lead to poor water quality. Many workers think that NO3‐N as a source for N can contribute to better plant growth in saline soils. The purpose of this work was to determine the necessity of NO3‐N and the ratio of NO3/ammonium (NH4) in the N fertilizer which gives higher productivity of the biomass yield of corn. Corn (Zea mays L.) plants (Var. LG11) were grown under saline soil conditions (8.5 dS m‐1), soils taken from the Euphrates valley (ACSAO Research Station) at Deir‐Ez‐Zor, east of Syria, from the surface layer of soil (0–25 cm). Five levels of N were applied in two forms, ammonium sulfate [15(NH4)2SO4] with enrichment (1.5% a) as the NH4‐N form and calcium nitrate [Ca(NO3)2] as the NO3‐N form, besides fixed amounts of phosphorus (P) and potassium (K) for all N treatments. The corn plants were harvested at the flowering stage (56 days old), oven dried, weighed, and analyzed for total N and 15N recovery. The results indicated that the dry matter weight for treatments which received a combination of NH4‐N and NO3‐N gave higher dry matter yield than a single treatment of one source of N. But, NO3‐N was more effective in improving yield than NH4‐N. Nitrogen recoveries on the basis of added and absorbed N derived from fertilizer were significantly more affected by NO3‐N than NH4‐N.  相似文献   

18.
The point at which nitrogen (N) applied approaches 100% recovery in the soil once plant and microbial sinks have been saturated has not been determined in winter wheat (Triticum aestivum L.) production systems. In dryland winter wheat, subsoil accumulation has not been found to occur until N rates exceed that required for maximum yield. Many conventional N rate experiments have not properly evaluated subsoil N accumulation due to the lack of equally spaced N rates at the high end of the spectrum over which accumulation is expected to occur. Therefore, the objectives of this study were to (i) determine when soil profile accumulation efficiencies reach 100% in continuous winter wheat production and (ii) to evaluate the potential for nitrate‐nitrogen (NO3 ‐N) leaching in continuous winter wheat when extremely high rates of fertilizer N are used. Two field experiments (T505 and T222) were conducted for two years using ten N rates (preplant‐incorporated) ranging from 0 to 5376 kg N ha1. No additional preplant fertilizer was applied in the second year. Following the first and second year wheat harvest, soil cores were taken to 2.4 m and bulk density, ammonium‐nitrogen (NH4‐N) and NO3‐N were determined. Crop N‐use efficiency (NUE) (N uptake treated ‐ N uptake check/rate applied) and soil profile inorganic N accumulation efficiencies (NAE) [net inorganic N accumulation in the soil profile/(fertilizer applied ‐ net N removed in the crop)] changed with fertilizer rate and were inversely related. Priming (increased net mineralization of organic N pools when low rates of fertilizer N are applied) may have occurred since increased NUE was observed at low N rates. The highest N‐accumulation efficiencies were at N rates of 168 and 448 kg ha‐1 in experiments T505 and T222, respectively. At both T222 and T505, no subsoil accumulation of NH4‐N or NO3‐N beyond 100 cm was observed for any of the N treatments when compared to the 0‐N check, even when N rates exceeded 448 kg ha‐1.  相似文献   

19.
Abstract

Field studies were conducted for four to seven years on two soils, Tangi silt loam (Typic Fragiudalf, fine‐silty, mixed, thermic) and Dexter loam (Ultic Hapludalf, fine‐silty, mixed, thermic), to determine the effects of phosphorus (P) applications on growth and nitrogen (N) content of white clover (Trifolium repens L.) and subterranean clover (Trifolium subterranum L.) and on ammonium (NH4 +)‐ and nitrate (NO3 ‐)‐N, total N, and organic carbon (C) levels in the soils at the end of the study. Phosphorus applications consistently and significantly increased forage yields and led to significantly higher N yields by the clovers. Increases in plant yields and N2‐fixation, however, were not reflected in higher soil N and C levels. On Tangi soil, NH4 +‐ and NO3 ‐‐N levels were lowest where no P was applied but no statistically significant differences (P < 0.05) were found among P rates above 20 kg/ha. On the Dexter soils, no significant differences were found at any P application level. Significant differences due to higher clover yields at increasing P rates were not found in total N or organic C . levels in either soil. Greenhouse evaluations showed no differences in bermuda‐grass yield, N concentration, or total N recovery despite increasing subclover yields in the field during the previous seven years. Harvesting nearly all above ground clover growth caused plant roots to be the major N and C contributor to the soil. It is possible that root production was not increased in proportion to forage production as P applications increased. Perhaps increased microbial activities and some leaching losses also minimized accumulations of N and C released by clover roots.  相似文献   

20.
Abstract

Fertilizer N recommendations for small grains are frequently based on soil test N but data is limited for irrigated spring wheat. The relative grain yield response of irrigated spring wheat to N as affected by inorganic soil N (NO3‐N and NH4‐N), yield potential and market class was evaluated in thirteen Southern Idaho field experiments involving N rates. Experiments were conducted on silt loam soils from 1978 to 1986. Preplant soil NO3‐N and NH4‐N to a depth of 60 cm and ranging from 27 to 142 kg/ha accounted for approximately 73% of the relative yield variability. NO3‐N and NH4‐N were significantly correlated (r=.72). NH4‐N with NO3‐N did not account for more of the relative yield variability than using NO3‐N alone.

Inorganic N in the first 30 cm and the second 30 cm were significantly correlated (r=.69) but N in the first depth increment accounted for more of the relative yield variability. The linear regression coefficient relating inorganic N in the first 30 cm to relative yield of unfertilized spring wheat was almost twice as high as the coefficient for the second 30 cm increment (.50 vs .27). Results indicate that inorganic N below 30 cm should be weighted differently than N in the first 30 cm when determining the N requirements of irrigated spring wheat.

Yield potential significantly affected the relative yield response to N. The response to N was not significantly affected by spring wheat market class (hard red vs soft white).

For estimating fertilizer N requirements, the results provide little justification for the current widespread practices of (1) using the combined NH4‐N and NO3‐N inorganic soil test N values when NO3‐N alone has as much predictive value and (2) assigning equal weight to inorganic soil N at all sampling depths.  相似文献   

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