Unfertilized Control Plots Research Articles

Validation of Fertilizer Requirement Map for Teff (<i>Eragrostis teff </i>(<i>Zucc.</i>)) at Lume District, East Shewa Zone, Oromia, Ethiopia

Ethiopia's teff production, a key cereal crop, has long suffered from blanket fertilizer recommendations that fail to account for the diverse soil conditions across the country. This often leads to suboptimal yields, falling short of the crop's true potential. To address this challenge, Batu Soil Research Center embarked on a ground breaking initiative: developing a phosphorus fertilizer requirement map specifically tailored to the Lume district. To validate the effectiveness of this map, field experiments were conducted across nine peasant associations within the district. Four different fertilizer treatments were compared: unfertilized control plots, plots receiving the conventional blanket recommendation of a uniform 100/100 NPS/Urea application, plots applying phosphorus based on the newly created map (P-map), and plots receiving phosphorus calculated based on individual soil analysis (P-required). The results were striking. P-map emerged as the clear winner, driving the highest yields of both grain (2178 kg ha<sup>-1</sup>) and biomass (6639 kg ha<sup>-1</sup>) compared to all other treatments. This impressive performance translated to a significant improvement in harvest index as well, reaching 34.11%. Notably, P-map surpassed not only the control group but also the blanket recommendation, highlighting the limitations of a one-size-fits-all approach. Economic analysis further solidified the case for P-map. For farmers in Lume district, adopting this map-based approach promises a 100% marginal rate of return, making it a highly profitable investment. This economic benefit, coupled with the substantial yield improvements, paves the way for a more sustainable and prosperous future for teff cultivation in the region. In conclusion, the fertilizer requirement map developed by Batu Soil Research Center holds immense potential for revolutionizing teff production in Ethiopia. By moving away from blanket recommendations and embracing a precision-driven approach, farmers in Lume district and beyond can unlock the full potential of this valuable crop, boosting their yields, income, and food security.

Assessment of soil microbial diversity and soil enzyme activities under inorganic input sources on maize and rice ecosystems

BackgroundTo increase crop productivity, modern agricultural practices comprises fertilizers, algaecides, herbicides and fungicides. ObjectiveThe purpose of this study was to evaluate the effects of soil microbial population and soil enzyme activity by the use of fertilizer in maize and inorganic input in the rice ecosystem. MethodsA field experiment (2021 to 2023) was carried out using synthetic fertilizer doses with maize crops followed by rice crops using inorganic inputs. Soil microbial population and enzyme activities were examined. ResultsMaize field experiment revealed that the plots treated with 75 % Standardized Dose of Fertilizer (SDF) of NPK had the highest populations of diazotrophs (124 × 105cfu / g), Phosphobacteria (66.33 × 105cfu / g), and Azospirillum (0.409 × 105 MPN / g) than 100 % and 150 % SDF of NPK. The soil enzyme activity was higher in the unfertilized control plot than fertilized plot. These experimental results revealed that a low amount of fertilizer and no fertilizers favour the growth of soil microorganisms and soil enzyme activities, respectively. Followed by the rice field experiment, revealed that the soil microbial population was decreased by the application of inorganic inputs viz., fertilizer, algaecide, herbicide and fungicide. However, the maximum soil microbial population was found in algaecide application followed by herbicide and fungicide. ConclusionThe field experiment concluded that soil microbial population and enzyme activity were affected by inorganic amendments. Less inorganic fertilizers and no fertilizers improve soil microbial activities and soil enzyme activities.

Pastures under dry climate can be cold spots for soil nitrous oxide emissions from grazing cattle excreta

Animal excreta is an important contributor to agricultural nitrous oxide (N2O) emissions – a potent greenhouse gas. Soil N2O emissions are episodic in nature and commonly subjected to large inter-annual and spatial variation. Thus, edaphic-climatic specific studies are needed to further our knowledge on global terrestrial N2O losses and to more accurately estimate national N2O emissions. For the Canadian Prairies, multi-year studies are needed for the determination of beef cattle dung and urine derived N2O emissions under semiarid and sub-humid climate and different soil types, a knowledge gap explored by the present study. We evaluated N2O emissions in dung, urine, and unfertilized control plots following six animal excreta applications in 2009/10 and 2010/11. The experiment was conducted in two locations: (i) Swift Current, Saskatchewan (semiarid prairies/brown Chernozem); and, ii) Lacombe, Alberta (sub-humid prairies/black Chernozem). Our results indicated that beef cattle dung-N derived N2O emission was negligible for all excreta applications on both sites as cumulative N2O emissions were not significantly different from the control plots (p > 0.05). Overall, cattle urine derived soil N2O emission was greater than emissions from dung and control plots, and subjected to large inter-annual variation. For the Swift Current site, 2010 experienced record-high precipitation that stimulated N2O emissions of up to 0.47% of the applied urine-N. Except for the applications exposed to record-high precipitation, the percentage of the urine-N lost as N2O at the Swift Current site was small, ranging from 0.00% to 0.01%. Similarly, for the Lacombe site, urine-N derived N2O emissions ranged from 0.00% to 0.12%, always lower than the 0.32% default IPCC (2019) emission factor used for cattle urine-N. Our results suggest that dry climate locations under near-normal or below-normal precipitation levels are natural “cold spots” for N2O emissions and could experience negligible cattle excreta derived soil N2O emissions.

Evaluation of the Dynamic Tube Method for Measuring Ammonia Emissions after Liquid Manure Application

Easy and inexpensive methods for measuring ammonia emissions in multi-plot field trials allow the comparison of several treatments with liquid manure application. One approach that might be suitable under these conditions is the dynamic tube method (DTM). Applying the DTM, a mobile chamber system is placed on the soil surface, and the air volume within is exchanged at a constant rate for approx. 90 s. with an automated pump. This procedure is assumed to achieve an equilibrium ammonia concentration within the system. Subsequently, a measurement is performed using an ammonia-sensitive detector tube. Ammonia fluxes are calculated based on an empirical model that also takes into account the background ammonia concentration measured on unfertilized control plots. Between measurements on different plots, the chamber system is flushed with ambient air and cleaned with paper towels to minimize contamination with ammonia. The aim of this study was to determine important prerequisites and boundary conditions for the application of the DTM. We conducted a laboratory experiment to test if the ammonia concentration remains stable while performing a measurement. Furthermore, we investigated the cleaning procedure and the effect of potential ammonia carryover on cumulated emissions under field conditions following liquid manure application. The laboratory experiment indicated that the premeasurement phase to ensure a constant ammonia concentration is not sufficient. The concentration only stabilized after performing more than 100 pump strokes, with 20 pump strokes (lasting approximately 90 s) being the recommendation. However, the duration of performing a measurement can vary substantially, and linear conversion accounts for those differences, so a stable concentration is mandatory. Further experiments showed that the cleaning procedure is not sufficient under field conditions. Thirty minutes after performing measurements on high emitting plots, which resulted in an ammonia concentration of approx. 10 ppm in the chamber, we detected a residual concentration of 2 ppm. This contamination may affect measurements on plots with liquid manure application as well as on untreated control plots. In a field experiment with trailing hose application of liquid manure, we subsequently demonstrated that the calculation of cumulative ammonia emissions can vary by a factor of three, depending on the degree of chamber system contamination when measuring control plots. When the ammonia background values were determined by an uncontaminated chamber system that was used to measure only control plots, cumulative ammonia emissions were approximately 9 kg NH3-N ha−1. However, when ammonia background values were determined using the contaminated chamber system that was also used to measure on plots with liquid manure application, the calculation of cumulative ammonia losses indicated approximately 3 kg NH3-N ha−1. Based on these results, it can be concluded that a new empirical DTM calibration is needed for multi-plot field experiments with high-emitting treatments.

Salt marsh vegetation change during a half-century of experimental nutrient addition and climate-driven controls in Great Sippewissett Marsh

Vegetative cover was mapped annually, 1976–2022, in experimental plots in Great Sippewissett Marsh, Cape Cod, USA, chronically fertilized at different doses, and subject to changes in sea level and other climate-related variables. Dominant species within areas of higher elevation in the plots followed different decadal trajectories: rise in sea level diminished cover of Spartina patens; higher N supplies increased cover of Distichlis spicata. The opportunistic growth response of D. spicata to high N supplies unexpectedly fostered increased platform accretion, a feature that persisted for succeeding decades and led to further changes in vegetation: D. spicata functioned as an effective ecosystem engineer with long-term ecological consequences. Shrubs usually found in upper marsh margins expanded into areas where D. spicata had stimulated accretion, then shaded and excluded D. spicata, but subsequently lost cover as sea level rise continued. Increased N supply converted stands of Spartina alterniflora, the dominant low marsh species, from short to taller ecophenotypes; sea level rise had minor effects on S. alterniflora, but during 2019–2022 appeared to reach a tipping point that fostered taller S. alterniflora and bare space even in un-fertilized control plots, and in Great Sippewissett Marsh in general. Model results anticipate that—in spite of potential accretion enhanced by vegetation and ecosystem engineer effects—there will be loss of high marsh, transient increases of low marsh, followed by loss of low marsh, and eventual conversion to shallow open water by the end of the century. Dire local projections match those of the plurality of recent reports from salt marshes around the world. Proposed management strategies may only delay unfortunate outcomes rather than maintain wetlands. Concerted reductions of warming from greenhouse gases, and lower N loads seem necessary to address the coming crises in wetlands—and many other environmental threats.

Role of fertilization regime on soil carbon sequestration and crop yield in a maize-cowpea intercropping system on low fertility soils

Achieving food security through intensive agricultural practices on low fertility soils is challenging as crop productivity is increasingly curtailed by the loss of soil structural stability and rapid depletion of soil organic carbon (SOC). As such, the conversion from traditional mono-cropping to legume-cereal intercropping, especially with integrated fertilization, may increase crop yields with the least ecological footprint. We set up a 2-year field experiment in a split-plot design with cowpea-maize monoculture and intercropping under different organic–inorganic fertilization regimes, including no fertilization (control), organic input only (compost), chemical input only (NPK), and multi-nutrient enriched compost (NPKEC). We observed that intercropped maize had a significantly higher biomass yield compared to the corresponding monoculture when fertilized with NPKEC fertilizer. However, cowpea biomass yield differences between monoculture and intercropped plots were comparable under all fertilization regimes. In contrast, the grain yield advantage of both maize and cowpea was significantly enhanced under the intercropping system compared to monoculture, with NPKEC showing the most significant effect among all fertilization regimes. When comparing the relative contribution of the fertilization regime to SOC, the NPKEC fertilizer provided the highest SOC-sequestration (0.30 Mg C/ha yr−1). At the same time, the effect of the cropping system on C-sequestration showed that intercropping provided the highest C-sequestration (0.17 Mg C/ha yr−1) compared to monocultures of both crops. Although compost application significantly increased mineral associated (MAOC) and particulate associated organic carbon (PAOC) concentrations compared to unfertilized control plots, NPKEC fertilization with intercropping system was the most effective combination causing the greatest increase of both soil C pools over time. Based on redundancy analysis (RDA), the positive association of MAOC and PAOC with C-sequestration suggests the importance of both organic fractions as primary C reservoirs conducting SOC storage. Importantly, although compost alone in association with intercropping had a lower C-sequestration, it was associated to a better soil structure as confirmed by its positive relationship with macro-and micro-aggregation, water stable aggregates (WSA), and mean weight diameter (MDA). Overall, our results indicate the importance of restoring soil structure in degraded soils through appropriate land management solutions, such as stoichiometrically balanced fertilization practices (NPKEC) and crop diversification (intercropping), in order to achieve significant gains in SOC storage and, ultimately, improve crop productivity.

Impact of Long-Term Nutrient Supply Options on Soil Aggregate Stability after Nineteen Years of Rice–Wheat Cropping System

Continuing soil degradation remains a serious threat to future food security. Soil aggregation can help protect soil organic matter from biodegradation; it affects soil physical (aeration), chemical (water infiltration), and biological (microbial) activities. The integrated plant nutrition system (IPNS) and organic farming (OF) options have been contemplated as a sustainable strategy to sustain soil aggregate stability under adverse climatic conditions and a possible tool to restore degraded soil systems. Results suggested that the application of plant nutrients based on IPNS and soil test crop response (STCR) including mineral fertilizers and organic manure (farmyard manure: FYM) improved soil aggregate stability and mean weight diameter (MWD) under rice–wheat cropping systems. A long-term (19 year) cropping system (rice–wheat) experiment was examined to identify best nutrient management practices. Seven nutrient supply options were applied: organic, mineral fertilizer in combination with IPNS, IPNS + B/IPNS + C to improve soil aggregate stability and MWD after completing 19 cropping cycles of rice–wheat cropping systems. Results showed that significantly higher (+31%) macroaggregates were dominant in the surface soil layer than in the subsurface soil. The significantly highest macroaggregates were observed under OF (60.12 g 100 g−1 dry soil) management practices followed by IPNS options. The MWD was significantly increased (+17%) between surface and subsurface soil. Maximum MWD was reported with OF (0.93 mm) management practices followed by the IPNS + C (0.78 mm), IPNS + B (0.77 mm), IPNS (0.70 mm), STCR (0.69 mm), NPK (0.67 mm), and unfertilized control (0.66 mm) plots. Overall, results suggest that the adoption of IPNS options, such as organic farming (OF), RDF, STCR, and inclusion of pulses (berseem and cowpea), significantly improved all soil aggregation fractions in the soil system and also offered an additional benefit in terms of soil sustainability.

Half-a-century effects of a slow-release nitrogen fertilizer, ureaformaldehyde, on stand growth and soil processes in a Scots pine stand

Slow-release nitrogen fertilizers have received little attention as alternatives to conventional fast-release fertilizers in N-limited boreal forests. Slow-release fertilizers better match the rate at which trees can uptake nutrients from the soil solution and are less likely to be vulnerable to losses to the environment. Ureaformaldehyde is a polymer that is synthesized from formaldehyde and urea and mainly used as a nitrogen fertilizer in lawns and greenhouse cultivations. Our goal was to assess ureaformaldehyde (UF) as a forest fertilizer. We aimed to determine its long-term effects on tree ring widths and stand basal area growth and how the effects differ from those of a conventional fast-release N fertilizer, ammonium nitrate (AN). We also attempted to determine whether the fertilizer additions changed soil organic matter properties in the long term. The study site was an unfertile Scots pine (Pinus sylvestris L.) stand with study plots with both fertilizer treatments that were performed 47 years ago and unfertilized control plots. As expected, AN addition resulted in a sharp increase in tree ring widths and the annual basal area increment that lasted for approximately seven years. UF addition caused a slower increase that lasted much longer, approximately 17 years. In addition, the UF addition showed indications that it slightly enhanced the growth even during the last decade. Our results also suggested that different fertilization treatments resulted in differences in tree size distribution. After almost a half century, some signs of UF-induced effects were still visible in soil organic matter; for instance, the humus layer in the UF treatment had a lower C-to-N ratio by 7 units than that in the humus layer of the AN treatment. In conclusion, slow-release ureaformaldehyde has a considerably longer effect on tree growth than conventional ammonium-nitrate fertilizer and, after almost a half century, there were signs that it still increased nitrogen availability for trees.

Impacts of long-term rice-based organic farming on fractions and forms of soil organic carbon and nitrogen in the Indo-Gangetic Plain

The present study aimed to appraise the long-term effects of organics, crop residues, and biofertilisers on soil carbon (C) and nitrogen (N) pools for sustainable crop production and changes in soil quality under long-term organic farming practices. Hence, we studied the soil C and N pools and their sensitivity indices as influenced by a different combination of farmyard manure, vermicompost, biofertilisers, and crop residue of rice, wheat, and mungbean, under long-term rice–wheat–mungbean (RWMCS) and rice–wheat (RWCS) cropping systems in an Inceptisol of India. Total soil organic C increased by 78% and 104% for RWMCS and 94% and 123% for RWCS with FYM + crop residue + biofertilisers and vermicompost + crop residue + biofertilisers, respectively over unfertilised control plots of RWMCS. The highly labile C and microbial biomass C were highly sensitive to management practices compared to total organic C and less labile C fractions. Integrated application of manures and crop residues in FYM + crop residue and VC + crop residue resulted in significantly higher total N, labile N, and mineral N for both cropping systems. Higher values of C and N management indexes were observed with FYM + crop residue + biofertilisers and VC + crop residue + biofertiliser in both cropping systems than other treatments. Integrated use of organic sources had higher N fractions than the unfertilised control plots, indicating that long-term conjoint use of organics, crop residues, and biofertilisers could sustain crop production and soil quality.

Response of bread wheat to sulfur and phosphorus fertilizers in the north central Ethiopia

BackgroundEmerging research evidences since few years back are indicating that sulfur (S) is becoming a limiting nutrient in some Ethiopian soils. However, these evidences are not sufficient to make a solid conclusion that some soils of Ethiopia have became deficient in S. There is also limited information on the interaction effects of S and phosphorus (P) on bread wheat in Ethiopia. Therefore, an experiment was conducted to evaluate the effects of S and P fertilizers; and their interaction on yield components and yield of bread wheat grown at Gerba and Deneba locations, Northern central Ethiopia. A factorial experiment consisting of three levels (0, 15 and 30 kg ha−1) of S and four levels (0, 11, 22 and 44 kg ha−1) of P was laid out in RCB design with three replications.ResultsResults revealed that yield components and yield of wheat were significantly affected by both main and interaction effects of S and P fertilizers in both locations. At Gerba, S applied at 15 and 30 kg ha−1 increased grain yield (GY) of wheat by 32 and 44% over untreated control treatment, respectively. The corresponding increases at Deneba were 29 and 37% over untreated control treatment, respectively. However, significantly higher GY was obtained with treatments involving combined application of S and P than that obtained with single application of S or P. GY gains due to S and P interaction effect ranged from 46–65 to 52–75% over untreated control treatment at Gerba and Deneba, respectively. Optimum GY of wheat was obtained with treatment involving 15 kg S ha−1 + 22 kg P ha−1.ConclusionThe results of this experiment revealed that application of P and S fertilizer has significantly increased yield component, grain and straw yield of wheat compared to unfertilized control plot, indicating insufficient soil P and S content for optimum production of wheat and this was confirmed by very low soil test values of S in both sites. Combined application of S and P produced significantly higher yield of wheat than that obtained with single application of S or P indicating synergistic interaction between these nutrients. In all cases, optimum grain and straw yield of wheat was obtained with treatment involving at 22 P + 15 S kg ha−1, while a partial budget analysis result revealed that a combination of 22P and 15S kg ha−1 produced the highest MMR (54.9%). Thus this treatment is found to be economically feasible treatment for bread wheat production in study area of the district.

Influence of Recycled Waste Compost on Soil Food Webs, Nutrient Cycling and Tree Growth in a Young Almond Orchard

Composting is an effective strategy to process agricultural and urban waste into forms that may be beneficial to crops. The objectives of this orchard field study were to characterize how a dairy manure compost and a food waste compost influenced: (1) soil nitrogen and carbon pools, (2) bacterial and nematode soil food webs and (3) tree growth and leaf N. The effects of composts were compared with fertilized and unfertilized control plots over two years in a newly planted almond orchard. Both dairy manure compost and food waste compost increased soil organic matter pools, as well as soil nitrate and ammonium at certain time points. Both composts also distinctly altered bacterial communities after application, specifically those groups with carbon degrading potential, and increased populations of bacterial feeding nematodes, although in different timeframes. Unique correlations were observed between nematode and bacterial groups within compost treatments that were not present in controls. Food waste compost increased trunk diameters compared to controls and had greater relative abundance of herbivorous root tip feeding nematodes. Results suggest that recycled waste composts contribute to biologically based nitrogen cycling and can increase tree growth, mainly within the first year after application.

Soil nutrients increase long-term soil carbon gains threefold on retired farmland.

Abandoned agricultural lands often accumulate soil carbon (C) following depletion of soil C by cultivation. The potential for this recovery to provide significant C storage benefits depends on the rate of soil C accumulation, which, in turn, may depend on nutrient supply rates. We tracked soil C for almost four decades following intensive agricultural soil disturbance along an experimentally imposed gradient in nitrogen (N) added annually in combination with other macro- and micro-nutrients. Soil %C accumulated over the course of the study in unfertilized control plots leading to a gain of 6.1MgCha-1 in the top 20cm of soil. Nutrient addition increased soil %C accumulation leading to a gain of 17.8MgCha-1 in fertilized plots, nearly a threefold increase over the control plots. These results demonstrate that substantial increases in soil C in successional grasslands following agricultural abandonment occur over decadal timescales, and that C gain is increased by high supply rates of soil nutrients. In addition, soil %C continued to increase for decades under elevated nutrient supply, suggesting that short-term nutrient addition experiments underestimate the effects of soil nutrients on soil C accumulation.

60 years of fertilization and liming impacts on soil organic carbon stabilization in a sub-tropical Alfisol.

Limited information is available on the C stabilization mechanism of tropical soils under different management practices including long-term organic manuring, mineral fertilization alone, or in combination with lime. Hence, to understand the effect of continuous application (for 60 years) of organic manure, fertilizer, and lime alone or in combination on an acidic Alfisol, stabilization of soil organic carbon (SOC) was evaluated under maize (Zea mays L.) wheat (Triticum aestivum L.) cropping. There were eight treatments that included farmyard manure (FYM) and nitrogen (N) applied in terms of FYM, additional dose of phosphorus (P) and potassium (K) applied in terms of inorganic fertilizer (FYM + P'K'), FYM + P'K' with liming (FYM + P'K' + L) and NPK alone. These treatments were laid in a randomized block design with three replications. Results indicated that FYM + P'K' plots had maximum amount of SOC inside large macroaggregates. The value was 33 and 92% greater than only minerally fertilized (NPK) and unfertilized control plots, respectively, whereas microaggregate-associated C was highest in plots with FYM + P'K' and lime (FYM + P'K' + L), which was 48 and 183% more than unfertilized control and NPK plots, respectively. Inside soil microaggregates, plots under FYM + P'K' had highest labile C, while NPK + L plots had highest recalcitrant C. Plots with organic amendments contained higher glomalin in large macroaggregates. Plots treated with FYM + P'K' had maximum intra-aggregate particulate organic matter within microaggregates inside macroaggregates (iPOM_mM), which was 28 and 74% higher than NPK and unfertilized control plots, respectively. Total C stock inside the protected microaggregates within macroaggregates was maximum for FYM + P'K' plots. It had 38, 67, and 171% higher C stock than NPK, FYM, and unfertilized control plots, respectively. Interestingly, despite estimated C input in FYM-treated plots was much higher than NPK plots, FYM-treated plots had less C stabilization within microaggregates and within microaggregates inside macroaggregates. Microaggregates within macroaggregates accounted for ~54% of the recalcitrant C content. Thus, macroaggregates stabilization through occlusion of microaggregates was accountable for sequestration of SOC and only FYM application did not promote that mechanism compared to NPK. Carbon stabilization within macroaggregates under FYM plots was mainly governed by amorphous iron oxide.

Global greenhouse vegetable production systems are hotspots of soil N2O emissions and nitrogen leaching: A meta-analysis.

Vegetable production in greenhouses is often associated with the use of excessive amounts of nitrogen (N) fertilizers, low NUE (15-35%), and high N losses along gaseous and hydrological pathways. In this meta-analysis, we assess the effects of application rate, fertilizer type, irrigation, and soil properties on soil N2O emissions and nitrogen leaching from greenhouse vegetable systems on the basis of 75 studies. Mean±standard error (SE) N2O emissions from unfertilized control plots (N2Ocontrol) and N leaching (NLcontrol) of greenhouse vegetable systems were 3.2±0.4 and 91±20kgN ha-1 yr-1, respectively, indicating legacy effects due to fertilization in preceding crop seasons. Soil organic carbon concentrations (SOC) and irrigation were significantly positively correlated with NLcontrol losses, while other soil properties did not significantly affect N2Ocontrol or NLcontrol. The annual mean soil N2O emission from fertilized greenhouse vegetable systems was 12.0±1.0kg N2O-N ha-1 yr-1 (global: 0.067Tg N2O-N yr-1), with N2O emissions increasing exponentially with fertilization. The mean EFN2O was 0.85%. The mean annual nitrogen leaching (NL) was 297±22kgN ha-1 yr-1 (global: 1.66TgN yr-1), with fertilization, irrigation, and SOC explaining 65% of the observed variation. The mean leaching factor across all fertilizer types was 11.9%, but 18.7% for chemical fertilizer. Crop NUE was highest, while N2O emissions and N leaching were lowest, at fertilizer rates <500kgN ha-1 year-1. Yield-scaled N2O emissions (0.05±0.01kg N2O-N Mg-1 yr-1) and nitrogen leaching (0.79±0.08kgN Mg-1 yr-1) were lowest at fertilizer rates <1000kgN ha-1 yr-1. Vegetables are increasingly produced in greenhouses, often under management schemes of extreme fertilization (>1500kgN ha-1 yr-1) and irrigation (>1200mm yr-1). Our study indicates that high environmental N2O and N leaching losses can be mitigated by reducing fertilization rates to 500-1000kgN ha-1 yr-1 (mean: ∼762kgN ha-1 yr-1) without jeopardizing yields.

Effects of Adapted N-Fertilisation Strategies on Nitrate Leaching and Yield Performance of Arable Crops in North-Western Germany

Groundwater pollution with nitrate is a big challenge for drinking water abstraction in regions with intensive agricultural land-use, specifically with high livestock densities on sandy soils in humid climates. Karst aquifers with high water flow velocities are extremely vulnerable to this problem. To cope with this situation, a field trial with an installation of ceramic suction cups under a randomised block design with a typical north-German cropping sequence of silage maize–winter wheat–winter barley was established in a karst water protection zone. Over three years, reduced nitrogen (N) application rates and N type (mineral or combined organic + mineral fertilisation) were tested for their effects on crop yields and leachate water quality below the root zone. Results showed no significant reductions in crop yields with 10/20% reduced N rates for cereals/maize and only slight reductions in cereal protein content. Nitrate concentration from adapted N rates was significantly lower in treatments with an application of organic fertilisers (−7.74 mg NO3-N l−1) with greatest potential after cultivation of maize; in only mineral fertilised plots the effect was smaller (−3.80 mg NO3-N l−1). Cumulative leaching losses were positively correlated with post-harvest soil mineral nitrogen content but even in unfertilised control plots losses &gt;50 kg N ha−1 were observed in some crop-years. Reduced N rates led to decreased leaching losses of 14% (6.3 kg N ha−1 a−1) with mineral and 29% (20.1 kg N ha−1 a−1) with organic + mineral fertilisation on average overall cops and years. The presented study revealed the general potential of adapted fertilisation strategies with moderately reduced N applications (−10/−20%) to increase leachate water quality without affecting significantly crop yields. However, regionally typical after-effects from yearlong high N surpluses in livestock intensive farming systems are a limiting factor.

Soil Organic Matter Degradation in Long-Term Maize Cultivation and Insufficient Organic Fertilization.

Soil organic matter carbon (CSOM) compounds degradation was observed in long-term field experiments with silage maize monoculture. Over a period of 26 years, the content of carbon in topsoil decreased by 22% in control unfertilized plots compared to 25% and 26% in treatments fertilized annually with mineral nitrogen. With annual wheat straw application (together with mineral N), the content of CSOM decreased by 8%. Contrary to that, the annual application of farmyard manure resulted in a CSOM increase of 16%. The ratio of carbon produced by maize related to total topsoil CSOM content ranged between 8.1–11.8%. In plots with mineral N fertilization, this ratio was always higher than in the unfertilized control plots. With the weaker soil extraction agent (CaCl2), the ratio of carbon produced by maize was determined to be 17.9–20.7%. With stronger extraction agent (pyrophosphate) it was only 10.2–14.6%. This shows that maize produced mostly unstable carbon compounds. Mineral N application resulted in stronger mineralization of original and stable organic matter compared to the unfertilized control. However, the increase of maize-produced carbon content in fertilized plots did not compensate for the decrease of “old” organic matter. As a result, a tendency to decrease total CSOM content in plots with mineral N applied was observed.

Long-term impacts of integrated nutrient management with equivalent nutrient doses to mineral fertilization on soil organic carbon sequestration in a sub-tropical Alfisol of India

Limited evidence is available on carbon sequestration potential of long-term integrated nutrient management (INM) versus mineral fertilization, when equivalent amounts of nutrients were added. Hence, this study was carried out to understand the impact of 60 years of INM with adjusted nutrient doses and mineral fertilization in an Alfisol in a maize (Zea mays L.)-wheat (Triticum aestivum L.) system on soil organic carbon (SOC) sequestration in surface (0–30 cm) and deep (30–60 cm) soil layers. Conventional tillage was done twice before sowing of both maize and wheat using a spade. In farmyard manure (FYM) and lime treated plots (FYMP'K'L: plots with nitrogen (N) applied in terms of FYM; additional dose of phosphorus (P) and potassium (K) and lime) total SOC concentration was nearly 83% higher than unfertilized control plots. The FYMP'K'L plots had ∼11% more total SOC concentration than plots treated with mineral fertilizer and lime (NPKL: recommended dose of N, P, K and lime) in the 0–30 cm soil layer. Labile C, including KMnO4-C, was more in plots with FYM than NPKL plots, whereas the recalcitrant C stock was more in NPKL than FYM treated plots. In the 0–60 cm soil layer, the labile C stock was highest in FYMP'K'L plots, but the recalcitrant C stock was highest in NPKL. Total SOC accumulation rate (over unfertilized control plots) was highest for FYMP'K'L plots (0.38 Mg ha−1 year−1) in the surface soil layer, whereas SOC sequestration rate was highest in NPKL plots (0.18 Mg ha−1 year−1) in the deep layer and in the 0–60 cm layer. Overall, although NPKL management practice had the highest C sequestration in the 0–60 cm layer, FYMP'K'L had the best CMI and labile C pools. Thus, resource poor farmers need not to use full doses of NPK and FYM for soil C management in the region.

Fertilization of Norway spruce forest with wood ash and nitrogen affected both tree growth and composition of chemical defence

AbstractWe fertilized a Norway spruce (Picea abies (L.) Karst.) stand on rich mineral soil with 3 t ha−1 of wood ash (ASH), 150 kg ha−1 of nitrogen (N) or a combination of wood ash and nitrogen (ASH + N), in addition to unfertilized control plots. After five growing seasons, we remeasured the trees and took core samples. Current- and previous-year needles were sampled and analyzed for total nitrogen and carbon, low-molecular weight phenolics and condensed tannins. Annual volume increment and standing volume were significantly higher in the ASH + N treatment than in control plots after 5 years. N gave a significant positive effect on basal area growth in the third year, after which the effect diminished. The ASH + N treated trees, on the other hand, showed an increasing basal area growth trend throughout the period. ASH reduced the total concentration of low-molecular weight phenolic compounds significantly in current-year needles. Phenolic acids increased under both ASH and ASH + N, while flavonoids decreased significantly under the same treatments compared to N. By including annual growth rate before fertilization in the analyses, the effect of N-treatment on flavonoids was positive only in trees with higher growth rates, and in those trees the concentration was higher than in both ASH-treated plots and controls. An acetophenone, constituting more than half of the total low-molecular weight phenolics concentration, was strongly reduced under all fertilization treatments. These results demonstrate that in addition to effects on tree growth, fertilization of the forest floor also has a strong influence on other metabolic processes of trees, with potential implications for ecosystem functioning.

Impact of nutrient supply on the relative development of yield components of winter wheat

In the long-term fertilization experiment, at Fülöpszállás, on calcic meadow chernozem soil we carried out experiments in seven growing seasons (2003/2004, 2004/2005, 2005/2006, 2006/2007, 2007/2008, 2008/2009, 2009/2010) with two winter wheat variety (GK Kalász, GK Petur,) in 4 replications, on 20 square meter random layout plots. The yield components were evaluated by kind of Sváb cumulative yield analysis. It can be determined that one-sided N, PK and NPK 2:1:1 rate applications had significant effect not only on yield of winter wheat, but also on yield components determining yield. Compare with the use of different nutrient rates it can be determined that in Fülöpszállás production site of high humus content, good P2O5 and K2O providing ability; in the case of one-sided N application only slightly, but under PK application higher increase in yield component could be realized compared to plants of unfertilized control plots. The NPK 2:1:1 rate application has spectacularly represented the cumulative effect of nutrients, as the appropriate rate of nutrients caused not only the aggregation of the effects of certain nutrient rates, but intensifying influences resulted in redoubling of its results. The higher rates of PK and certain 2:1:1 rate NPK treatments increase the values of yield components only to a lower extent compared to control treatment.

Long-term fertilisation impact on temperature sensitivity of aggregate associated soil organic carbon in a sub-tropical inceptisol

Understanding impact of long-term fertilisation on soil aggregation, carbon (C) stabilisation and temperature sensitivity of soil organic C (SOC) mineralisation are necessary to foresee C dynamics. The present study was conducted in an Inceptisol under wheat (Triticum aestivum) based cropping system, with the objective to quantify the effect of 44 years of integrated nutrient management on soil aggregation, enzymatic activity, and temperature sensitivity (Q10) of SOC. Treatments were: unfertilised control (UC), 100% recommended dose of nitrogen (N), N and phosphorus (NP), N, P and potassium (NPK), integrated application of NPK and farmyard manure (FYM) (NPKF) and 150% recommended dose of N, P and K (1.5NPK). The observed data were analysed using analysis of variance for randomized block design and Tukey’s HSD test (P < 0.05) was used for mean separation. In the 0–15 cm soil layer, plots under NPKF had ˜121 and 19% larger macroaggregate-associated C than UC and NPK plots, respectively. Irrespective of soil depth and temperature, higher cumulative C mineralisation was observed for NPKF (by ˜67-91%) and NPK (by ˜42-56%) treated plots than UC. Activation energies for SOC decomposition in 0–15 cm bulk soil were ˜205, and 258% higher in NPKF, and 1.5NPK, respectively, than UC plots. Mean Q10 of macroaggregate-C was higher than microaggregate-C. Aggregate-C of sub-surface soil was more temperature sensitive than surface soil, possibly due to higher recalcitrant/total SOC in the subsurface than surface layer. Thus, it reveals the need of better C management practices to augment the lability of C in subsurface soil layers. Plots under NPKF had higher β–glucosidase and fluorescein diacetate activities in bulk soils and aggregates over NPK in the both layers. NPKF application is recommended for improved soil aggregation, SOC protection within macroaggregates, enzyme activities in bulk soils and aggregates and capable for less proportional SOC decomposition than NPK or UC plots at higher temperature. Thus, soil management involving organic manure application and mineral fertilisers would enhance the activation energy of SOC and act as a barrier for SOC decomposition by facilitating soil aggregation and enhance SOC sequestration.