Nitrogen Fertilizer Replacement Value of Concentrated Liquid Fraction of Separated Pig Slurry Applied to Grassland

Seven grassland experiments on sandy and clay soils were performed during a period of 4 years to estimate the nitrogen (N) fertilizer replacement value (NFRV) of concentrated liquid fractions of separated pig slurry (mineral concentrate: MC). The risk of nitrate leaching when applying MC was compared to when applying mineral fertilizers. Grassland yields in 2009–2012 fertilized with MC were compared with grassland fertilized with two mineral fertilizers: granulated calcium ammonium nitrate and liquid ammonium nitrate (LAN). The mineral fertilizers comprised 50% nitrate-N and 50% ammonium-N, and MC comprised 95–100% ammonium-N. Treatment application rates included zero N and three incremental rates of N fertilization. The liquid fertilizers were shallow injected (0–5 cm). The NFRV of MCs was 75% on sandy and 58% on clay soil with granulated ammonium nitrate as reference, and 89% on sandy and 92% on clay soil with LAN as reference. Risk of nitrate leaching after application of MC, measured in residual soil mineral N post-growing season and N in the upper groundwater in the following spring, was equal to that for mineral fertilizers.     

Role of organic fractions on C decomposition and N mineralization of animal wastes in soil

The relative contributions of water-soluble, water-non-soluble, Van Soest-soluble, and neutral detergent fiber (NDF) fractions of pig slurry (PS), cattle slurry (CS), cattle farmyard manure (FYM), and composted cattle farmyard manure (CFYM) to the overall C and N mineralization of the raw wastes were studied by incubating treated soil for 107 days at 15°C under non-limiting N conditions. The C or N mineralization of soluble fractions was calculated from the difference between C or N mineralization of the raw and non-soluble fractions. The organic N content of raw wastes ranged from 15 to 32 mg N g⁻¹ dry matter and organic C to organic N ratio from 13 to 29. The water-soluble fraction (SOL_W) was close to 100 mg C g⁻¹ raw waste C for CS, FYM, and CFYM but reached 200 mg C g⁻¹ for PS. The Van Soest-soluble fraction (SOL_VS) was the main fraction for PS, CS, and CFYM (>500 mg C g⁻¹ raw waste C) but only 303 mg C g⁻¹ raw waste C for FYM. Both soluble and non-soluble fractions contributed to C decomposition of slurries, with half to more than half of the decomposed C derived from the degradation of soluble compounds. Most of the C decomposed from FYM was derived from the large NDF fraction, but the contribution from the water-soluble C to the decomposition was also significant. Carbon mineralization of CFYM was due to the degradation of the NDF fraction, whereas soluble C did not contribute. Amounts of N mineralized or immobilized by raw wastes and non-soluble fractions at the end of incubation were significantly correlated (P < 0.01) with their organic C to organic N ratio. The contribution of the Van Soest-soluble fraction to N mineralization varied greatly between the four wastes. Finally, large differences in the C degradability and N availability of the water and Van Soest-soluble fractions were demonstrated.     

Nitrogen and phosphorus in runoff from grassland with buffer strips following application of fertilizers and manures

Abstract. We examined whether nitrogen (N) and phosphorus (P) export was enhanced from grassland receiving inorganic fertilizer and manures typical of intensive livestock production. Buffer strips were included in the study to determine if they could reduce nutrient export. Hillslope plots receiving granular inorganic fertilizer, liquid cattle slurry and solid cattle manure (FYM) were compared using rainfall simulation for 4 storms on consecutive days at 22 mm h^-1 and 35 minutes duration. The plots were hydrologically isolated in a randomized block layout of 4 treatments × 3 replicates and measured 30 × 5m; the upper 20m received either fertilizer, slurry or FYM, while the lower 10 m acted as an unfertilized grass buffer strip. Nitrogen and P export in surface runoff from grassland receiving inorganic fertilizer exceeded that from FYM or slurry treatments; concentrations up to46mgN1-^-1 and 15 mgP1^–1 were recorded.
Sixty eight % and 62% of the N from FYM and slurry respectively, was exported in organic form. Seventy four % (FYM) and 39% (slurry) of the P was in particulate or dissolved organic form. The buffer strip reduced N export in surface runoff by 94% and P export by 98% from inorganic fertilizer plots. A 75% reduction in N export was recorded from the buffer zone below slurry plots but only a 10% reduction in P, with most P remaining in the particulate or dissolved organic fraction. There was no significant difference in N export from the buffer zone between the inorganic fertilizer treatment and the untreated control.     

Pig slurry treatment modifies slurry composition,N2O,and CO2 emissions after soil incorporation

The treatment of manures may improve their agricultural value and environmental quality, for instance with regards to greenhouse gases mitigation and enhancement of carbon (C) sequestration. The present study verified whether different pig slurry treatments (i.e. solid/liquid separation and anaerobic digestion) changed slurry composition. The effect of the slurry composition on N₂O and CO₂ emissions, denitrification and soil mineral nitrogen (N), after soil incorporation, was also examined during a 58-day mesocosm study. The treatments included a non-treated pig slurry (NT), the solid fraction (SF), and the liquid fraction (LF) of a pig slurry and the anaerobically digested liquid fraction (DG). Finally, a non-fertilized (N0) and a treatment with urea (UR) were also present.The N₂O emissions measured represented 4.8%, 2.6%, 1.8%, 1.0% and 0.9% of N supplied with slurry/fertilizer for NT, LF, DG, SF and UR, respectively. Cumulative CO₂ emissions ranged from 0.40 g CO₂-C kg^?1 soil (0.38 Mg CO₂-C ha^?1) to 0.80 g CO₂-C kg^?1 soil (0.75 Mg CO₂-C ha^?1). They were highest for SF (56% of C applied), followed by NT (189% of C applied), LF (337% of C applied) and DG (321% of C applied). Ammonium was detected in the soil for all treatments only at day one, while nitrate concentration increased linearly from day 15 to day 58, at a rate independent of the type of slurry/fertilizer applied. The nitrate recovery at day 58 was 39% of the N applied for NT, 19% for SF, 52% for LF, 67% for DG, and 41% for UR. The solid fraction generally produced higher potential denitrification fluxes (75.3 for SF, 56.7 for NT, 53.6 for LF, 47.7 for DG and 39.7 mg N₂O + N₂-N kg^?1 soil for UR). The high variability of actual denitrification results obfuscated any treatment effect.We conclude that treatment strongly affects slurry composition (mainly its C, fibre and NH₄⁺ content), and hence N₂O and CO₂ emission patterns as well as denitrification processes and nitrate availability. In particular, the solid fraction obtained after mechanical separation produced the most pronounced difference, while the liquid fraction and the anaerobically digested liquid fraction did not show significant difference with respect to the original slurry for any of the measured parameters. Combining data from the different fractions we showed that separation of slurry leads to reduced N₂O emissions, irrespective of whether the liquid fraction is digested or not. Furthermore, our results suggested that the default emission factor for N₂O emissions inventory is too low for both the non-treated pig slurry and its liquid fraction (digested or not), and too high for the separated solid fraction and urea.     

Does acidification increase the nitrogen fertilizer replacement value of bio‐based fertilizers?

Acidification of manure, digestate and their processed derivatives has been proposed as a technique to, amongst others, mitigate ammonia emissions related to application in the field. The current study investigated whether acidification of (1) pig slurry (PS), (2) liquid fraction of pig slurry (LFPS), (3) digestate (DIG), and (4) liquid fraction of digestate (LFDIG) increases their nitrogen (N) fertilizer replacement value (NFRV) as compared to non‐acidified counterparts, a synthetic N fertilizer (calcium ammonium nitrate; CAN) and an unfertilized control. Product performance was evaluated from the perspective of (1) crop development (yield, nutrient uptake, and crop quality assessment) via a pot experiment with Lactuca sativa L. and (2) soil N dynamics [net N release (N_rel,net) and net N mineralization] via a soil incubation experiment. Crop yield of pots receiving bio‐based fertilizers performed ‘on par' with CAN as compared to unfertilized control, implying that bio‐based fertilizers derived from digestate or manure could potentially play a role in replacing synthetic N fertilizers. However, our findings also suggest that acidification did not result in an increased use efficiency of applied N. NFRVs of acidified products were below those of non‐acidified products and CAN, with crop yield on average 6–13% and 11–18% lower compared to non‐acidified products and the CAN treatment, respectively. A possible explanation for lower performance as compared to non‐acidified products could be an inhibitory delay in the N_rel,net, which in our experimental design proved to be negative for crops with short production cycles. This pattern was revealed in the incubation experiments in which N_rel,net in acidified products remained below that of non‐acidified, in this study tentatively attributed to immobilization of mineral N. However, this negative effect on N availability should be reaffirmed in crops with longer production cycles. Finally, some interesting findings with regard to plant composition also warrant further in‐depth investigation, e.g ., Zn uptake by lettuce in acidified treatments was significantly higher than that of non‐acidified treatments. This implies that product pre‐treatment may play a future role in biofortification and amelioration of (trace) element composition of crops (arguably for crops with longer production cycles). Improving crop nutritional value by increased uptake of micronutrients is receiving increasing attention.     

Application technique affects the potential of mineral concentrates from livestock manure to replace inorganic nitrogen fertilizer

It has been suggested that mineral concentrates (MCs) produced from livestock manure might partly replace inorganic N fertilizers, thereby further closing the nitrogen (N) cycle. Here, we quantified nitrogen use efficiency (NUE) and N loss pathways associated with MCs, compared with inorganic fertilizer and manure. In a 26‐day greenhouse experiment with ryegrass (Lolium perenne L.), the effects of application technique (surface application vs. injection) and N source (control, two types of MC, three inorganic fertilizers or pig slurry) were compared. We measured yield, ammonia volatilization, nitrous oxide emission and denitrification. With surface application, NUE for MCs (38% for MC1 and 22% for MC2) was significantly lower than for calcium ammonium nitrate (CAN; 61%) and comparable with PS (25%). This was most likely due to higher ammonia emissions. After injection, the NUE of MC was comparable with that of CAN. Denitrification and N₂O emission from surface‐applied MC were comparable with those from surface‐applied PS. After injection, MC behaved similarly to inorganic fertilizers. We conclude that MCs should be injected to maximize NUE and to fulfil their potential as inorganic fertilizer replacement. Significant NUE differences between MCs suggest the possibility for further optimization of the MC production process.     

Leaching of nitrate and phosphorus after autumn and spring application of separated solid animal manures to winter wheat

Animal slurry can be separated into solid and liquid manure fractions to facilitate the transport of nutrients from livestock farms. In Denmark, untreated slurry is normally applied in spring whereas the solid fraction may be applied in autumn, causing increased risk of nitrate and phosphorus (P) leaching. We studied the leaching of nitrate and P in lysimeters with winter wheat crops (Triticum aestivum L.) after autumn incorporation versus spring surface application of solid manure fractions, and we compared also spring applications of mineral N fertilizer and pig slurry. Leaching was compared on a loamy sand and a sandy loam soil. The leaching experiment lasted for 2 yr, and the whole experiment was replicated twice. Nitrate leaching was generally low (19–34 kg N/ha) after spring applications of mineral fertilizer and manures. Nitrate leaching increased significantly after autumn application of the solid manures, and the extra nitrate leached was equivalent to 23–35% of total manure N and corresponded to the ammonium content of the manures. After spring application of solid manures and pig slurry, only a slight rise in N leaching was observed during the following autumn/winter (<5% of total manure N). Total P leaching was 40–165 g P/ha/yr, and the application of solid manure in autumn did not increase P leaching. The nitrogen fertilizer replacement value of solid manure N was similar after autumn and spring application (17–32% of total N). We conclude that from an environmental perspective, solid manure fractions should not be applied to winter wheat on sandy and sandy loam soils under humid North European conditions.     

Aggregate associated carbon, nitrogen and sulfur and their ratios in long-term fertilized soils

Farmyard manure (FYM) and fertilizer applications are important management practices used to improve nutrient status and organic matter in soils and thus to increase crop productivity and carbon (C) sequestration. However, the long-term effects of fertilization on C, nitrogen (N) and sulfur (S) associated with aggregates, especially on S are not fully understood. We investigated the effects of more than 80 years of FYM (medium level of 40 Mg ka⁻¹ and high level of 60 Mg ka⁻¹) and mineral fertilizer (NPKS and NK) on the concentrations and pools of C, N, and S and on their ratios in bulk soil, dry aggregates and water stable aggregates on an Aquic Eutrocryepts soil in South-eastern Norway. A high level of FYM and NPKS application increased the proportion of small dry aggregates (<0.6 mm) by 8%, compared with the control (without fertilizer). However, both medium and high level of FYM application increased the proportion of large water stable aggregates (>2 mm) compared with mineral fertilizer (NPKS and NK). The total C and N pools in bulk soils were also increased in FYM treatments but no such increase was seen with mineral fertilizer treatments. The increased total S pool was only found under high level of FYM application. Water stable macroaggregates (>2 and 1–2 mm) and microaggregates (<0.106 mm) contained higher concentrations of C, N and S than the other aggregate sizes, but due to their abundance, medium size water stable aggregates (0.5–1 mm) contained higher total pools of all three elements. High level of FYM application increased the C concentration in water stable aggregates >2, 0.5–1 and <0.106 mm, and increased the S concentration in most aggregates as compared with unfertilized soils. Higher C/N, C/S and N/S ratios were found both in large dry aggregates (>20 and 6–20 mm) and in the smallest aggregates (<0.6 mm) than in other aggregate sizes. In water stable aggregates, the C/N ratio generally increased with decreasing aggregate size. However, macroaggregates (>2 mm) showed higher N/S ratios than microaggregates (<0.106 mm). We can thus conclude, that long-term application of high amounts of FYM resulted in C, N and S accumulation in bulk soil, and C and S accumulation in most aggregates, but that the accumulation pattern was dependent on aggregate size and the element (C, N and S) considered.     

The impact of exogenous organic matter on SOM contents and microbial soil quality

Eight fertilization strategies were compared in a field trial on Alfisol in Belgium (humid temperate climate): cattle slurry (CSL); farmyard manure (FYM); vegetable, fruit and garden waste compost (VFG); high C/N farm compost (FCP1); low C/N farm compost (FCP2); exclusively mineral fertilizer (MIN N); no fertilization (NF+), no fertilization and no crop (NF?). After five growing seasons, VFG resulted in the highest soil organic C (1.46% SOC) and total N contents (0.117%TN). SOC and TN contents of the MIN N plots, on the other hand, remained unchanged and were even similar to those of NF+ plots, despite greater biomass production on the MIN N plots than on the NF+ plots. Application of organic matter mostly increased dehydrogenase, β-glucosidase and β-glucosaminidase activity, but only FYM raised the activity of all three enzymes significantly compared to MIN N. Of the five organic amendments tested, only VFG suppressed Rhizoctonia solani (65% suppressiveness). Plots treated with FCP1, on the other hand, were highly conducive to R. solani (28.3% suppressiveness). Suppressiveness against R. solani probably depended on the maturity and cellulose content of the organic amendments. Highest microbial biomass C contents were found in the VFG plots. PLFA 16:1ω5c contents sensitively reacted to the different treatments and were significantly higher in VFG than in MIN N plots (3.84 and 2.20 nmol g^?1 dry soil, respectively). Finally, a soil quality index was developed using stepwise canonical discriminant analysis. β-glucosaminidase and β-glucosidase activity, and TN content were the most important parameters of the index. According to this index, FYM resulted in a significantly higher soil quality than the other treatments. We conclude that farmyard manure seems to be the preferred organic amendment for maintaining soil quality in arable fields under temperate climatic conditions.     

Slurry field management and ammonia emissions under Mediterranean conditions

In Spain, farmers are interested in applying pig (Sus scrofa domesticus) slurry (PS) to their fields throughout the year. During the spring and summer months, ammonia (NH₃) volatilization may be high. We studied the potential range of NH₃ losses under a warm and a hot period of the year, using available field practices, and two strategies: PS directly incorporated into the soil, in spring (I‐spring); and PS applied by splash‐plate, in summer time (SP‐summer), both to bare soil. Measurements were conducted, after PS application, using the micrometeorological mass balance integrated horizontal flux method. The cumulative NH₃‐N volatilization was 35% (I‐spring) and 60% (SP‐summer) of total ammonium nitrogen applied, and half of the total NH₃‐N losses happened by 17 h and 8 h, respectively, after application. Incorporation strategy was less effective in avoiding NH₃ losses than is described in the literature. This fact has important consequences for the implementation of NH₃ mitigation measures in Mediterranean agricultural systems.     

Manure management practices applied to a seven‐course rotation on a sandy soil: effects on nitrate leaching

This experiment tested whether it was possible to incorporate broiler litter (BL) or cattle farmyard manure (FYM) into a 7‐yr arable rotation on a sandy soil without causing an increase in nitrate‐nitrogen (NO₃‐N) leaching. Four manure treatments (with adjusted fertilizer inputs), varying in frequency and timing of application, were imposed on the rotation and compared with a control that received inorganic fertilizer according to recommended rates. Over seven winters, the annual average NO₃‐N leached from the inorganic fertilizer treatment (control) was 39 kg/ha in 183 mm drainage. Total manure N loadings over the period of the experiment ranged between 557 and 1719 kg/ha (80–246 kg/ha/yr) for the four treatments. Three of the four manure treatments significantly increased NO₃‐N leaching over the rotation (P < 0.001). Annual applications of FYM (1719 kg/ha manure N or 246 kg/ha/yr) increased NO₃‐N leaching by 39%. We hypothesize that this was due to increased mineralization of the organic N accumulating from repeated FYM applications. BL applied each year (1526 kg/ha manure N or 218 kg N/ha/yr) increased NO₃‐N leaching by 52% above the control; BL applied 5 of 7 yr (972 kg/ha manure N or 139 kg N/ha/yr on average) and including inadvisable autumn applications increased leaching by 50%. BL applied in late winter or early spring every 2–3 yr (557 kg/ha manure N or 80 kg N/ha/yr on average) resulted in NO₃‐N leaching similar to the control. This suggests that to avoid additional NO₃‐N leaching from manure use in an arable rotation, manure should not be applied every year and autumn applications should be avoided; there are real challenges where manure is used on an annual basis.     

Enhancing phosphorus availability,soil organic carbon,maize productivity and farm profitability through biochar and organic–inorganic fertilizers in an irrigated maize agroecosystem under semi‐arid climate

Biochar amendments offer promising potential to improve soil fertility, soil organic carbon (SOC) and crop yields; however, a limited research has explored these benefits of biochar in the arid and semi‐arid regions. This two‐year field study investigated the effects of Acacia tree biomass‐derived biochar, applied at 0 and 10 t ha^?1 rates with farmyard manure (FYM) or poultry manure (PM) and mineral phosphorus (P) fertilizer combinations (100 kg P ha^‐1), on maize (Zea mays L.) productivity, P use efficiency (PUE) and farm profitability. The application of biochar with organic–inorganic P fertilizers significantly increased soil P and SOC contents than the sole organic or inorganic P fertilizers. Addition of biochar and PM as 100% P source resulted in the highest soil P (104% increase over control) and SOC contents (203% higher than control). However, maize productivity and PUE were significantly higher under balanced P fertilizer (50% organic + 50% mineral fertilizer) with biochar and the increase was 110%, 94% and 170% than 100%‐FYM, 100%‐PM and 100% mineral fertilizer, respectively. Maize productivity and yield correlated significantly positively with soil P and SOC contents These positive effects were possibly due to the ability of biochar to improve soil properties, P availability from organic–inorganic fertilizers and SOC which resulted in higher PUE and maize productivity. Despite the significant positive relationship of PUE with net economic returns, biochar incorporation with PM and mineral fertilizer combination was economically profitable, whereas FYM along biochar was not profitable due to short duration of the field experiments.     

Nitrous oxide emissions from grassland in an intensive dairy farm in the Basque Country of Spain

Abstract. Intensively managed grasslands are potentially a large source of N₂O in the North Coast of Spain because of the large N input, the wet soil conditions and mild temperatures. To quantify the effect of fertilizer type and management practices carried out by farmers in this area, field N₂O losses were measured over a year using the closed chamber technique. Plots received two types of fertilizer: cattle slurry (536 kg N ha^–1) and calcium ammonium nitrate (140 kg N ha^–1). N₂O losses were less in the slurry treatment than after mineral fertilizer. This was probably due to high, short‐lived peaks of N₂O encountered immediately following mineral N addition. In contrast, the seasonal distribution of N₂O losses from the slurry amended plot was more uniform over the year. The greater N₂O losses in the mineral treatment might have been enhanced by the combined effect of mineral fertilizer and past organic residues present from previous organic amendments. Weak relationships were found between N₂O emission rates and soil nitrate, soil ammonium, soil water content and temperature. Better relationships were obtained in the mineral treatment than in the slurry plots, because of the wider range in soil mineral N. Water filled pore space (WFPS) was a key factor controlling N₂O emissions. In the > 90% WFPS range no relationships were found. The best regressions were found for the mineral treatment in the 40–65% WFPS range, 49% of the variance being explained by soil nitrate and ammonium content. In the 65–90% WFPS range, 43% of the variance was explained by nitrate only, but the inclusion of soil ammonium did not improve the model as it did in the 40–65% WFPS range. This fact indicates that nitrification is likely to be an important process involved in N₂O emissions at the 40–65% WFPS.     

Phosphorus Enriched Organic Amendments can Increase Nitrogen Use Efficiency in Wheat

Although nitrogen (N) has the highest requirement for plant growth, N use efficiency (NUE) seldom exceeds 40%. NUE may be improved by integrated application of fertilizer N and enriched organic amendments. The present experiment aimed to test the extent of increase in NUE by integrated application of fertilizer N farmyard manure (FYM) and rock phosphate enriched compost (RPEC). Mineralization kinetics and N release from FYM and RPEC were studied by an incubation experiment. Results revealed that maximum potentially mineralizable N as well as N release (283.9, 186.7 mg kg^?1 soil, respectively) were from RPEC + fertilizer N treated soils, followed by FYM + fertilizer N. Maximum yield, N uptake, and N recovery were obtained from RPEC + fertilizer N treated soils followed by FYM + fertilizer N. Soils treated with RPEC had shown significantly higher dehydrogenase activity than FYM treated soils. Thus, RPEC might increase yield as well as NUE over FYM. N uptake by plant at maximum tillering stage and flowering stage of wheat correlated positively (R² > 0.85) with the decay rate (k and kN₀) parameter of incubation experiment suggesting their relevance as indicators of plant available N.     

Nitrate leaching loss following application of organic manures to sandy soils in arable cropping.

Abstract. Experiments were set up at two sites to measure nitrogen (N) leaching loss from applications of separated pig/cattle slurry and cattle farmyard manure(FYM), during winters 1990/91–1993/94 (site A) and from broiler litter and FYM, during winters 1990/91–1992/93 (site B). The manures were applied at a target rate of 200 kg ha^-1 total N during the autumn and winter to overwinter fallow or top dressed onto winter rye. The total N in leachate was calculated from leachate N concentrations, in samples collected using ceramic cups buried at 90 cm, and an estimate of drainage volume. Nitrogen losses were greatest following manure applications in September, October and November but losses following applications in December or January were not significantly elevated above those from untreated controls. Losses were consistently lower from FYM than from broiler litter or separated slurry. The presence of a cover crop (winter rye) significantly reduced overall N leaching compared with the fallow, but only reduced the manure N leaching losses at one site during one winter when a high proportion of drainage occurred late. The incorporation of a nitrification inhibitor (DCD) with manures applied in October did not significantly reduce the manure N leaching.     

Nitrogen mineralization and CO2 and N2O emissions in a sandy soil amended with original or acidified pig slurries or with the relative fractions

The following six pig slurries obtained after acidification and/or solid/liquid separation were used in the research: original (S) and acidified (AS) pig slurry, nonacidified (LF) and acidified (ALF) pig slurry liquid fraction, and nonacidified (SF) and acidified (ASF) pig slurry solid fraction. Laboratory incubations were performed to assess the effect of the application of these slurries on N mineralization and CO₂ and N₂O emissions from a sandy soil. Acidification maintained higher NH₄ ⁺-N contents in soil particularly in the ALF-treated soil where NH₄ ⁺-N contents were two times higher than in LF-treated soil during the 55–171-day interval. At the end of the incubation (171 days), 32.9 and 24.2 mg N kg⁻¹ dry soil were mineralized in the ASF- and SF-treated soils, respectively, but no mineralization occurred in LF- and S-treated soils, although acidification decreased N immobilization in ALF- (−25.3 mg N kg⁻¹ soil) and AS- (−12.7 mg N kg⁻¹ soil) compared to LF- (−34.4 mg N kg⁻¹ soil) and S-treated (−18.6 mg N kg⁻¹ soil) soils, respectively. Most of the dissolved CO₂ was lost during the acidification process. More than 90% of the applied C in the LF-treated soil was lost during the incubation, indicating a high availability of the added organic compounds. Nitrous oxide emissions occurred only after day 12 and at a lower rate in soils treated with acidified than nonacidified slurries. However, during the first 61 days of incubation, 1,157 μg N kg⁻¹ soil was lost as N₂O in the AS-treated soil and only 937 in the S-treated soil.     

Residual effects of pig slurry applied to a Mediterranean soil on yield and N uptake of a subsequent wheat crop

Abstract. In areas of intensive pig farming, fresh pig slurry is often applied annually to the same fields. Thus, to avoid nitrogen (N) losses correct fertilizer practice should take account of residual effects of slurry on the following crops. The residual effects of different rates of slurry applied during three years were evaluated in subsequent wheat crops. The experiment was conducted on an irrigated Mediterranean Typic Xerofluvent soil, where plots were left unfertilized or fertilized with 150 kg N ha⁻¹ as ammonium nitrate. Grain yield and grain N uptake increased with slurry rates in both fertilized and unfertilized treatments. The increases in the unfertilized treatments were interpreted as a nitrogen effect of the previous 1996–98 slurry applications. The equivalent mineral N released from the pig slurry was underestimated by two existing decay-series approaches. Although decay-series are useful tools for estimating manure residual effects they should be adjusted for local conditions. A significant positive relationship was detected between apparent N use efficiency of the slurry and the total amount of applied organic N, which was interpreted as a specific residual effect rather than due to the N dose of previously applied pig slurry.     

The fate of nitrogen,phosphorus and potassium in long‐term experiments in Skierniewice

On the basis of long‐term fertilization experiments in Skierniewice, being conducted since 1923 at the Experimental Field of Warsaw Agricultural University, the fate (or balance) of nitrogen for a period of 35 years and that of phosphorus and potassium for 20 years, was studied. The balance includes N, P and K rates applied in mineral fertilizers and farmyard manure (FYM), uptake of these nutrients by the crop plants and the changes in the content of total N and total P and of slow release K in the soil during that time. The nitrogen balance shows a loss of this nutrient of 11—14 kg N ha^—1 y^—1, which corresponds to 15% of the applied ammonium nitrate on fields without FYM but to 23% on fields with FYM, in spite of crop yields being considerably greater on fields treated with FYM. The phosphorus balance indicated that in the 0—70 cm soil layer less than 4% of P from superphosphate was not found. In the treatment not fertilized with potassium for many years, the plants took up 49 kg K ha^—1 y^—1 from slow release forms because the fraction of available K did not change during that period. When calculating the potassium balance only 1.6% of K from potash salt were not found in plots without FYM but 12.3% of the applied KCl were not recovered in treatments with FYM. The comparison of the P‐ and K‐uptake from organic and mineral fertilizer in the two crop rotations indicates a higher P‐ and K‐efficiency from FYM than from inorganic fertilizer.     

华北潮土冬小麦-夏玉米轮作包气带氮素淋溶机制

合理水氮管理可以实现作物目标产量和品质、维持土壤肥力和降低环境污染。然而,自20世纪90年代以来,我国农田过量施氮和大水漫灌等问题突出,引起农业面源污染日趋加重,地下水硝酸盐污染成为一个普遍现象。本文以华北潮土区冬小麦-夏玉米体系为研究对象,采用数据整合和文献分析的方法,阐明了典型农田硝态氮淋溶的时空特征及影响因素,研究了地表裂隙和土壤大孔隙对硝态氮淋溶的影响,定量了氮素在地表-根层-深层包气带-地下水的垂直迁移通量及过程。结果表明,农户常规管理的冬小麦-夏玉米轮作体系氮素盈余较高(299～358kg·hm~(-2)·a~(-1)),导致土壤根区和深层包气带累积了大量的硝态氮。冬小麦季硝态氮的迁移主要受灌溉影响,以非饱和流为主,且迁移距离较短;春季单次灌溉量低于60 mm,可以有效控制水和硝态氮淋溶出根区。冬小麦耕作和灌溉引起的地表裂隙对水氮运移的贡献不大。雨热同期的夏玉米季,土壤水分经常处于饱和状态,再降雨就可以导致硝态氮淋溶出根层进入深层包气带。夏玉米季极易发生硝态氮淋溶事件(占全年总淋溶事件的81%左右),硝态氮淋溶量占全年总淋溶量的80%左右,且单次淋溶事件的淋溶量较高。大孔隙优先流对夏玉米季根区硝态氮淋溶的贡献率在71%左右,这些硝态氮脱离了作物根系吸收范围,反硝化作用对硝态氮去除具有一定作用。在华北气候-土壤条件下,特别应注意冬小麦收获后土壤不应残留过多硝态氮,以避免夏玉米季降雨发生大量淋溶;夏玉米季需要注意施氮与作物需氮的匹配。由于夏玉米追肥困难,生产上提倡一次性施肥措施,控释肥应该能够发挥更大作用。未来气候变化,导致夏季极端高强度降雨事件的频率增加,将会加剧包气带累积硝态氮通过饱和流或优先流向地下水的迁移。合理的水氮管理是从源头上减少硝态氮向深层包气带和地下水迁移的主要措施。     

Uptake of cobalt and manganese by winter wheat from a sandy loam soil with and without added farmyard manure and fertilizer nitrogen

Abstract

The influence of three rates of nitrogen (N) fertilizer on the availability of native cobalt (Co) and manganese (Mn) for winter wheat grown on a sandy loam soil with (FYM) and without (Non‐FYM) farmyard manure was studied in a field experiment Increased N fertilization resulted in higher rates of Co and Mn uptake by the crop. The effect was higher in the field which received farmyard manure compared to that which has not. Winter wheat developed significant (P<0.01) differences in the rate of uptake for Co and Mn between the two fields. The main vareiation between the sites couled be explained by the history of FYM application which was able to explain 28% of the total nitrate (NO₃) cocentration found in the soil solution.