Cereal yield and quality as affected by nitrogen availability in organic and conventional arable crop rotations: A combined modeling and experimental approach

The effects of nitrogen (N) availability related to fertilizer type, catch crop management, and rotation composition on cereal yield and grain N were investigated in four organic and one conventional cropping systems in Denmark using the FASSET model. The four-year rotation studied was: spring barley–(faba bean or grass-clover)–potato–winter wheat. Experiments were done at three locations representative of the different soil types and climatic conditions in Denmark. The three organic systems that included faba bean as the N fixing crop comprised a system with manure (stored pig slurry) and undersowing catch crops (OF + C + M), a system with manure but without undersowing catch crops (OF ? C + M), and a system without manure and with catch crops (OF + C ? M). A grass-clover green manure was used as N fixing crop in the other organic system with catch crops (OG + C + M). Cuttings of grass-clover were removed from the plots and an equivalent amount of total-N in pig slurry was applied to the cropping system. The conventional rotation included mineral fertilizer and catch crops (CF + C + F), although only non-legume catch crops were used. Measurements of cereal dry matter (DM) at harvest and of grain N contents were done in all plots. On average the FASSET model was able to predict the yield and grain N of cereals with a reasonable accuracy for the range of cropping systems and soil types studied, having a particularly good performance on winter wheat. Cereal yields were better on the more loamy soil. DM yield and grain N content were mainly influenced by the type and amount of fertilizer-N at all three locations. Although a catch crop benefit in terms of yield and grain N was observed in most of the cases, a limited N availability affected the cereal production in the four organic systems. Scenario analyses conducted with the FASSET model indicated the possibility of increasing N fertilization without significantly affecting N leaching if there is an adequate catch crop management. This would also improve yields of cereal production of organic farming in Denmark.     

Nitrogen use efficiency and residual effect of fertilizers with nitrification inhibitors

Blending fertilizers with nitrification inhibitors (NI) is a technology to reduce nitrogen (N) losses. The application of NI could increase the soil N supply capacity over time and contribute to an enhancement of N use efficiency (NUE) in some cropping systems. The objectives were to determine in a field experiment located in Central Spain (i) the effect of NI-fertilizers applied to maize (Zea mays L.) during two seasons on yield, N content and NUE compared to conventional fertilizers, (ii) the soil residual effect of NI-fertilizers in a non-fertilized sunflower (Helianthus annuus L.) planted during a third season, and (iii) the possible sources of residual N via laboratory determinations. The maize was fertilized with ammonium sulfate nitrate (ASN) and DMPP (3,4-dimethylpyrazole phosphate) blended ASN (ENTEC^®) at two levels (130 and 170 kg N ha⁻¹). A control treatment with no added N fertilizer was included to calculate NUE. The second year, DMPP application allowed a 23% reduction of the fertilizer rate without decreasing crop yield or grain quality. In addition, the sunflower planted after the maize scavenged more N in treatments previously treated with ENTEC^® than with traditional fertilizers, increasing NUE in the cropping systems. After DMPP application, N was conserved in non-ready soil available forms during at least one year and subsequently released to meet the sunflower crop demand. The potential N mineralization obtained from aerobic incubation under controlled conditions of soil samples collected before sunflower sowing was higher for ENTEC^® than ASN or control treatments. A higher δ¹⁵N in the soil indicated larger non-exchangeable NH₄⁺ fixation in soils from the plots treated with ENTEC^® or ASN-170 than from the ASN-130 or the control. These results open the opportunity to increase NUE by designing crop rotations able to profit from the effect of NI on the soil residual N.     

Biological nitrogen fixation in three long-term organic and conventional arable crop rotation experiments in Denmark

Biological nitrogen (N) fixation (BNF) by legumes in organic cropping systems has been perceived as a strategy to substitute N import from conventional sources. However, the N contribution by legumes varies considerably depending on legumes species, as well as local soil and climatic conditions. There is a lack of knowledge on whether the N contribution of legumes estimated using short-term experiments reflects the long-term effects in organic systems varying in fertility building measures. There is also limited information on how fertilizer management practices in organic crop rotations affect BNF of legumes. Therefore, this study aimed to estimate BNF in long-term experiments with a range of organic and conventional arable crop rotations at three sites in Denmark varying in climate and soils (coarse sand, loamy sand and sandy loam) and to identify possible causes of differences in the amount of BNF. The experiment included 4-year crop rotations with three treatment factors in a factorial design: (i) rotations, i.e. organic with a year of grass-clover (OGC), organic with a year of grain legumes (OGL), and conventional with a year of grain legumes (CGL), (ii) with (+CC) and without (−CC) cover crops, and (iii) with (+M) and without (−M) animal manure in OGC and OGL, and with (+F) mineral fertilizer in CGL. Cover crops consisted of a mixture of perennial ryegrass and clover (at the sites with coarse sand and sandy loam soils) or winter rye, fodder radish and vetch (at the site with loamy sand soil) in OGC and OGL, and only perennial ryegrass in CGL at all sites. The BNF was measured using the N difference method. The proportion of N derived from the atmosphere (%Ndfa) in aboveground biomass of clover grown for an entire year in a mixture with perennial ryegrass and harvested three times during the growing season in OGC was close to 100% at all three sites. The Ndfa of grain legumes in both OGL and CGL rotations ranged between 61% and 95% depending on location with mostly no significant difference in Ndfa between treatments. Cover crops had more than 92% Ndfa at all sites. The total BNF per rotation cycle was higher in OGC than in OGL and CGL, mostly irrespective of manure/fertilizer or cover crop treatments. There was no significant difference in total BNF between OGL and CGL rotations, but large differences were observed between sites. The lowest cumulated BNF by all the legume species over the 4-year rotation cycle was obtained at the location with sandy loam soil, i.e. 224–244, 96–128, and 144–156 kg N ha⁻¹ in OGC, OGL and CGL, respectively, whereas it was higher at the locations with coarse sand and loamy sand soil, i.e. 320–376, 168–264, and 200–220 kg N ha⁻¹ in OGC, OGL and CGL, respectively. The study shows that legumes in organic crop rotations can maintain N₂ fixation without being significantly affected by long-term fertilizer regimes or fertility building measures.     

The effect of tillage system and residue management on grain yield and nitrogen use efficiency in winter wheat in a cool Atlantic climate

The effects of soil tillage and straw management systems on the grain yield and nitrogen use efficiency of winter wheat (Triticum aestivum L. em. Thell.) were evaluated in a cool Atlantic climate, in central Ireland between 2009 and 2011. Two tillage systems, conventional tillage (CT) and reduced tillage (RT) each with and without incorporation of the straw of the preceding crop, were compared at five levels of fertiliser N (0, 140, 180, 220 and 260 kg N ha⁻¹).CT had a significantly higher mean grain yield over the three years but the effect of tillage varied between years. Yields did not differ in 2009 (Year 1), while CT produced significantly higher grain yields in 2010 (Year 2), while RT produced the highest yields in 2011 (Year 3). Straw incorporation had no significant effect in any year.Nitrogen application significantly increased the grain yields of all establishment treatment combinations. Nitrogen use efficiency (NUE) ranged from 14.6 to 62.4 kg grain (85% DM) kg N ha⁻¹ and decreased as N fertiliser rate was increased.The CT system had a significantly higher mean NUE over the three years but the effect of tillage varied with years. While there was no tillage effect in years 1 and 3, CT had a significantly higher NUE than RT in year 2. Straw management system had minimal effect on NUE in any year.The effect of tillage and N rate on soil mineral N content also varied between years. While there was no tillage effect in years 1 and 3, RT had significantly larger soil N contents than CT in the spring before N application, and post-harvest in year 2. N application rates had no effect on soil N in year 1, increased residual N content in year 2 and had an inconsistent effect in year 3. Straw management had no significant effect on soil mineral N content.These results indicate that RT establishment systems can be used to produce similar winter wheat yields to CT systems in a cool Atlantic climate, providing weather conditions at establishment are favourable. The response to nitrogen is similar with both tillage systems where the crop is successfully established. Straw management system has very little effect on crop performance or nitrogen uptake.     

Optimisation of fertiliser rates in crop production against energy use indicators

Optimising mineral nitrogen (N) use in crop production is inevitable target as mineral fertilisers reflect one of the highest inputs both in terms of economy and energy. The aim of the study was to compare the relationship between the rate of N fertiliser application and different measures of energy parameters exemplary data for spring-wheat in boreal climate condition in Estonia in 2006–2010. The effect of mineral N with rates 0, 40, 80, 120 and 160 kg N ha⁻¹ was studied on the background of composted cow manure and without organic fertilisers. Univalent parameters, energy gain (EG) (energy output − energy input) and energy ratio (ER) (energy output/energy input) were calculated. To aggregate parameters with different units (ER and EG) we proposed two standardisation approaches for combined indices. ER maximisation gave both organic fertilisation background optimum N norms significantly lower than EG (p < 0.05) optimisation. Both the new combined indices gave optimum N norms in between the rate of ER an EG. Composted cow manure background did not affect mineral N optimisation significantly. We suggest optimisation of mineral N according to bi-dimensional parameters as they capture important features of production efficiency and are more objective using as advisory tool for sustainable production systems.     

Winter cereal yields as affected by animal manure and green manure in organic arable farming

The effect of nitrogen (N) supply through animal and green manures on grain yield of winter wheat and winter rye was investigated from 1997 to 2004 in an organic farming crop rotation experiment in Denmark on three different soil types varying from coarse sand to sandy loam. Two experimental factors were included in the experiment in a factorial design: (1) catch crop (with and without), and (2) manure (with and without). The four-course crop rotation was spring barley undersown with grass/clover – grass/clover – winter wheat or wheat rye – pulse crop. All cuttings of the grass–clover were left on the soil as mulch. Animal manure was applied as slurry to the cereal crops in the rotation in rates corresponding to 40% of the N demand of the cereal crops.Application of 50 kg NH₄–N ha^?1 in manure increased average wheat grain yield by 0.4–0.9 Mg DM ha^?1, whereas the use of catch crops did not significantly affect yield. The use of catch crops interacts with other management factors, including row spacing and weed control, and this may have contributed to the negligible effects of catch crops. There was considerable variation in the amount of N (100–600 kg N ha^?1 year^?1) accumulated in the mulched grass–clover cuttings prior to ploughing and sowing of the winter wheat. This was reflected in grain yield and grain N uptake. Manure application to the cereals in the rotation reduced N accumulation in grass–clover at two of the locations, and this was estimated to have reduced grain yields by 0.1–0.2 Mg DM ha^?1 depending on site. Model estimations showed that the average yield reduction from weeds varied from 0.1 to 0.2 Mg DM ha^?1. The weed infestation was larger in the manure treatments, and this was estimated to have reduced the yield benefit of manure application by up to 0.1 Mg DM ha^?1. Adjusting for these model-estimated side-effects resulted in wheat grain yields gains from manure application of 0.7–1.1 Mg DM ha^?1.The apparent recovery efficiency of N in grains (N use efficiency, NUE) from NH₄–N in applied manure varied from 23% to 44%. The NUE in the winter cereals of N accumulated in grass–clover cuttings varied from 14% to 39% with the lowest value on the coarse sandy soil, most likely due to high rates of N leaching at this location. Both NUE and grain yield benefit in the winter cereals declined with increasing amounts of N accumulated in the grass–clover cuttings. The model-estimated benefit of increasing N input in grass–clover from 100 to 500 kg N ha^?1 varied from 0.8 to 2.0 Mg DM ha^?1 between locations. This is a considerably smaller yield increase than obtained for manure application, and it suggests that the productivity in this system may be improved by removing the cuttings and applying the material to the cereals in the rotation, possibly after digestion in a biogas reactor.Cereal grain protein content was increased more by the N in the grass–clover than from manure application, probably due to different timing of N availability. Green-manure crops or manures with a relatively wide C:N ratio may therefore be critical for ensuring sufficiently high protein contents in high yielding winter wheat for bread making.     

The effect of organic and conventional management on the yield and quality of wheat grown in a long-term field trial

The performance of winter wheat was evaluated under organic (ORG) and conventional (CON) management systems in the Nafferton Factorial Systems Comparison (NFSC) long-term field trial. The present study separates out the crop protection and fertility management components of organic and conventional production systems using two levels each of crop protection (CP) and fertility management (FM). The experimental design provided the four combinations of crop protection and fertility (CON-CP CON-FM, CON-CP ORG-FM, ORG-CP CON-FM and ORG-CP ORG-FM) to evaluate their effects on yield, quality (protein content and hectolitre weight) and disease levels during the period 2004–2008. The conventional management system (CON-CP CON-FM) out-yielded the organic management system (ORG-CP ORG-FM) in all years by an average of 3.1 t ha⁻¹, i.e. 7.9 t ha⁻¹ vs. 4.8 t ha⁻¹. Fertility management was the key factor identified limiting both yield and grain protein content in the ORG management system. The CON-FM produced on average a 3% higher protein content than ORG-FM in all years (12.5% vs. 9.7%). However the ORG-CP system produced higher protein levels than CON-CP although it was only in 2008 that this was statistically significant. In contrast to protein content it was ORG-FM which produced a higher hectolitre weight than the CON-FM system (71.6 kg hl⁻¹ vs. 71.0 kg hl⁻¹). The clear and significant differences in yield and protein content between the ORG-FM and CON-FM systems suggest a limited supply of available N in the organic fertility management system which is also supported by the significant interaction effect of the preceding crop on protein content. The pRDA showed that although fertilisation had the greatest effect on yield, quality and disease there was also a considerable effect of crop protection and the environment.     

Steps toward alternative farming system in rice

An experiment was conducted on rice, in old alluvial soil zone, with bio-fertilizer and different doses of organic manure and chemical fertilizer to develop an alternative farming system which is productive, profitable, enhances soil health and conserves the natural resources over a long term. The experiment was conducted for four consecutive years (2007–2010) and it has been observed that 40% N and 25% P chemical fertilizer can safely be supplemented by low-cost, natural resource based bio-fertilizer (Azotobacter sp. and PSB) at 12 kg ha⁻¹ and organic manure (FYM) at 10.00 t ha⁻¹ to achieve long-term sustainability in rice cultivation that is more productive and profitable.     

Achieving legislation requirements with different nitrogen fertilization strategies: Results from a long term experiment

The Nitrates Directive (91/676/EEC, Anonymous, 1991) was developed in Europe to limit environmental threats from intensive livestock farming and N fertilizer applications to crops. It imposed several rules on farmers and public bodies, one of which was nutrient fertilization plan adoption. Here we use results from the Tetto Frati (Northern Italy) Long-Term Experiment to verify the terms and coefficients in the official Italian guidelines and evaluate the limitations imposed to organic fertilization amounts. For this purpose, we mined long-term experimental data of crop yield, N uptake, N use efficiency, and soil organic matter content from miscellanea cropping systems fertilized with farmyard manure (FYM) and bovine slurry (SLU), typical of a dairy farm in Northern Italy. N fertilization efficiency indicators (Removal to Fertilizer ratio, Apparent Recovery and Nitrogen Fertilizer Replacement Value) indicated that in the long run, FYM behaved similarly to urea, and better than SLU. Even N supply rates as high as 250 kg N ha⁻¹ were justified by high rates of crop removal. In fact, among the terms of the mass-balance equation, SOM mineralization was found to be most relevant, followed by meadow rotation residual effects. We conclude that a revised Nitrates Directives application scheme could be more relaxed in its application limit of manure-N, but should be more ambitious in setting efficiency coefficients for manure fertilization.     

Organic amendment and minimum tillage in winter wheat grown in Mediterranean conditions: Effects on yield performance,soil fertility and environmental impact

The experiment was conducted to evaluate the agronomic benefit of the application of organic fertilizers combined with different soil tillage on quantitative and qualitative components of winter wheat (Triticum durum Desf., cv. ‘Simeto’) and on chemical soil fertility parameters. The environmental impact, due to heavy metals introduced in soil-plant system, was further investigated. Soil tillage treatments consisted of conventional (CT) and minimum tillage (MT). Fertilization treatments were: mineral at 100 kg N ha⁻¹ (N_min); municipal solid waste compost at 100 kg N ha⁻¹ (N_comp); 50 kg N ha⁻¹ of both compost and mineral fertilizers (N_mix); sewage sludge at 100 kg N ha⁻¹ (N_ss). These treatments were compared with an unfertilized control (N₀). No significant difference was observed between the two soil tillage treatments for quantitative yield production, while among the fertilization treatments N_ss did not show any significant difference compared to N_min. At the end of the research, the fertility of the soil (oxidable carbon, total nitrogen, available phosphorus) was on average higher in N_comp and N_ss treatments compared to the N₀ and N_min ones. The overall distribution of heavy metals in soil-plant system respect to the different fertilizer treatments has not allowed to grouped their effects with Principal Components Analysis. This result showed that the amount of potential pollutants applied by organic amendments did not modified the dynamic equilibrium of the soil–plant system. The MT, as well as the fertilization with the application of sewage sludge (N_ss), allowed to reach productive performance similar to conventional management (CT with N_min). Here we demonstrate that, in the short term period, sustainable agronomical techniques can replace the conventional one with environmental benefit.     

Nitrogen uptake and N-use efficiency of Mediterranean cotton under varied deficit irrigation and N fertilization

Efficient N management is essential to optimize yields and reduce degradation of the environment, but requires knowledge of deficit irrigation effects on crop yields and crop N outputs. This study assessed the N content and N-use efficiency of cotton over the 2008 and 2009 growing seasons in a single field site of the Thessaly Plain (central Greece). The experiment consisted of nine treatments with three fertilizer rates (60, 110 and 160 kg N ha⁻¹) split into three irrigation levels (approx. 1.0, 0.7 and 0.4 of the amount applied by the producer). Reduced water supply induced a shift in the distribution of N within the plant with seeds becoming an N sink under conditions of water stress. Total crop N increased linearly with irrigation level and reached a maximum average of 261 and 192 kg N ha⁻¹ in 2008 and 2009, respectively. Fertilizer application did not trigger a crop N or yield response and indicated that N inputs were in excess of crop needs. Variation in weather patterns appeared to explain annual differences of nitrate-N in the top soil and N uptake by the crop.The index of lint production efficiency (iNUE) detected crop responses caused by irrigation and annual effects, but failed to account for excessive N inputs due to mineral fertilizer applications. A maximum average iNUE of 9.6 was obtained under deficit irrigation, whereas an iNUE of 8.1 was obtained under 40 cm irrigation when crop N uptake was not excessive (192 kg ha⁻¹ in 2009). In contrast, NUE, as an estimator of N recovery efficiency, identified excessive fertilizer inputs as N losses to the environment and indicated that 60 kg N ha⁻¹ was a rate of high N removal efficiency and long-term N balance. However, NUE failed to account for crop N responses to irrigation and weather/management patterns. In this case study, neither index was able to detect all the factors influencing the N mass balance and both were required in order to provide a comprehensive evaluation of the environmental performance of our cropping system.     

Delayed permanent water rice production systems do not improve the recovery of 15N-urea compared to continuously flooded systems

Crop recovery of nitrogen (N) fertiliser in flooded rice systems is low relative to fertiliser N recoveries in aerobic crops, and the N losses have environmental consequences. Recent water shortages across the globe have seen a move towards alternative water management strategies such as delayed permanent water (DPW, also known as delayed flood). To investigate whether N fertiliser regimes used in DPW systems result in greater recovery of N fertiliser than traditional continuously flooded (CF) rice systems, we conducted a multi-N rate field trial using ¹⁵N-labelled urea. Around 27% of the ¹⁵N-labelled fertiliser was recovered in aboveground biomass at maturity, regardless of water regime or N fertiliser rate, and approximately 20% recovered in the soil to 300 mm depth. Plants in the CF system accumulated more total N at each rate of applied N fertiliser than plants in the DPW system due to greater exploitation of native soil N reserves, presumably because the earlier application of N fertiliser in the CF systems led to greater early growth and higher crop N demand. The greater crop biomass production as a result of higher N uptake in the CF system did not increase grain yields above those observed in the DPW system, likely due to cold weather damage. In the following season at the same site, a single N rate (150 kg N ha⁻¹) trial found no significant differences in crop N uptake, biomass yields, grain yields or ¹⁵N-labelled urea recovery in DPW, CF and drill sown-CF (DS-CF) treatments. However, owing to higher ¹⁵N fertiliser recovery in the 0–100 mm soil horizon, total plant + soil recovery of ¹⁵N was significantly higher in the CF treatment (63%) than the DS-CF and DPW treatments (around 50% recoveries). The loss of 40–50% of the applied N (presumably as NH₃ or N₂) in both seasons regardless of watering regime suggests that new fertiliser N management strategies beyond optimising the rate and timing of urea application are needed, particularly in light of increasing N fertiliser prices.     

Effects of irrigation and nitrogen fertilization on the greenhouse gas emissions of a cropping system on a sandy soil in northeast Germany

Irrigation induces processes that may either decrease or increase greenhouse gas emissions from cropping systems. To estimate the net effect of irrigation on the greenhouse gas emissions, it is necessary to consider changes in the crop yields, the content of soil organic carbon and nitrous oxide emissions, as well as in emissions from the use and production of machinery and auxiliary materials. In this study the net greenhouse gas emissions of a cropping system on a sandy soil in northeast Germany were calculated based on a long-term field experiment coupled with two-year N₂O flux measurements on selected plots. The cropping system comprised a rotation of potato, winter wheat, winter oil seed rape, winter rye and cocksfoot each under three nitrogen (N) fertilization intensities with and without irrigation. Total greenhouse gas emissions ranged from 452 to 3503 kg CO_2-eq ha⁻¹ and 0.09 to 1.81 kg CO_2-eq kg⁻¹ yield. Application of an adequate amount of N fertilizer led to a decrease in greenhouse gas emissions compared to zero N fertilization whereas excessive N fertilization did not result in a further decrease. Under N fertilization there were no significant differences between irrigation and non-irrigation. Increases in greenhouse gas emissions from the operation, production and maintenance of irrigation equipment were mainly offset by increases in crop yield and soil organic carbon contents. Thus, on a sandy soil under climatic conditions of north-east Germany it is possible to produce higher yields under irrigation without an increase in the yield-related greenhouse gas emissions.     

Evaluation of monocropped and intercropped grain legumes for cover cropping in no-tillage and reduced tillage organic agriculture

Intensive tillage by means of mouldboard ploughing can be highly effective for weed control in organic farming, but it also carries an elevated risk for rapid humus decomposition and soil erosion. To develop organic systems that are less dependent on tillage, a two-year study at Reinhardtsgrimma and Köllitsch, Germany was conducted to determine whether certain legume cover crops could be equally successfully grown in a no-till compared with a reduced tillage system. The summer annual legumes faba bean (Vicia faba L.), normal leafed field pea (Pisum sativum L.), narrow-leafed lupin (Lupinus angustifolius L.), grass pea (Lathyrus sativus L.), and common vetch (Vicia sativa L.) were examined with and without sunflower (Helianthus annuus L.) as a companion crop for biomass and nitrogen accumulation, symbiotic nitrogen fixation (N₂ fixation) and weed suppression. Total cover crop biomass, shoot N accumulation and N₂ fixation differed with year, location, tillage system and species due to variations in weather, inorganic soil N resources and weed competition. Biomass production reached up to 1.65 and 2.19 Mg ha⁻¹ (both intercropped field peas), and N₂ fixation up to 53.7 and 60.5 kg ha⁻¹ (both common vetches) in the no-till and reduced tillage system, respectively. In the no-till system consistently low sunflower performance compared with the legumes prevented significant intercropping effects. Under central European conditions no-till cover cropping appears to be practicable if weed density is low at seeding. The interactions between year, location, tillage system and species demonstrate the difficulties in cover crop species selection for organic conservation tillage systems.     

Effect of biogas digestate,animal manure and mineral fertilizer application on nitrogen flows in biogas feedstock production

The expansion of biogas feedstock cultivation may affect a number of ecosystem processes and ecosystem services, and temporal and spatial dimensions of its environmental impact are subject to a critical debate. However, there are hardly any comprehensive studies available on the impact of biogas feedstock production on the different components of nitrogen (N) balance. The objectives of the current study were (i) to investigate the short-term effects of crop substrate cultivation on the N flows in terms of a N balance and its components (N fertilization, N deposition, N leaching, NH₃ emission, N₂O emission, N recovery in harvested product) for different cropping systems, N fertilizer types and a wide range of N rate, and (ii) to quantify the N footprint of feedstock production in terms of potential N loss per unit of methane produced. In 2007/08 and 2008/09, two field experiments were conducted at two sites in Northern Germany differing in soil quality, where continuous maize (R1), maize–whole crop wheat followed by Italian ryegrass as a double crop (R2), and maize–grain wheat followed by mustard as a catch crop (R3) were grown on Site 1 (sandy loam), and R1 and a perennial ryegrass ley (R4) at Site 2 (sandy soil rich in organic matter). Crops were supplied with varying amounts of N (0–360 kg N ha⁻¹, ryegrass: 0–480 kg N ha⁻¹) supplied as biogas digestate, cattle slurry, pig slurry or calcium-ammonium nitrate (CAN).Mineral-N fertilization of maize-based rotations resulted in negative N balances at N input for maximum yield (Nopt), with R2 having slightly less negative balances than R1 and R3. In contrast, N balances were close to zero for cattle slurry or digestate treatments. Thus, trade-offs between substrate feedstock production and changes of soil organic matter stocks have to be taken into consideration when evaluating biogas production systems. Nitrogen losses were generally dominated by N leaching, whereas for the organically fertilized perennial ryegrass ley the ammonia emission accounted for the largest proportion. Nitrogen balance of the ryegrass ley at Nopt was close to zero (CAN) or highly positive (cattle slurry, digestate). Nitrogen footprint (NFP) was applied as an eco-efficiency measure of N-loss potential (difference of N input and N recovery) related to the unit methane produced. NFP ranged between −11 and +6 kg N per 1000 m³ methane at Nopt for maize-based rotations, without a significant impact of cropping system or N fertilizer type. However, for perennial ryegrass ley, NFP increased up to 65 kg N per 1000 m³. The loose relation between NFP and observed N losses suggests only limited suitability for NFP.     

An analysis of agricultural sustainability of cropping systems in arable and dairy farms in an intensively cultivated plain

In Lombardy region (northern Italy) agricultural systems are mostly based on cereals and forage crops, and are normally intensively cultivated. To monitor and analyse the most important agri-environmental issue of this area (water pollution by nitrates and plant protection products, non-renewable fossil energy exploitation, weed dynamics), we conducted an integrated agronomic, environmental and economic assessment of arable and dairy farming using indicators.The structural and management data about farming and cropping systems were collected by periodic interviews over a 3-year period in seven (three arable and four dairy) representative farms.The nitrogen surplus calculated at field scale ranged from low (27 kg N ha^?1) to high (339 kg N ha^?1) values, depending by the amount of chemical and organic fertilisers applied. Fossil inputs ranged from 11.2 to 46.0 GJ ha^?1; the highest values were due to the high use of machinery and chemical inputs. The efficiency factor in energy transformation (an indicator of the dependence of food and feed production on non-renewable energy) ranged from 5.0 to 12.2. Large variability was also observed for economic performance (gross margin; from -364 to 1078 € ha^?1). The lowest values were observed where the total costs of production (fixed and variable) were elevated. The simplification of cropping systems was responsible for a high probability of weed populations development. The values of Load Index, an indicator describing the potential toxicity of plant protection products on non-target organisms, showed an elevated use of active substances due to the dominance of maize.The indicator-based assessment, founded on a relatively simple data collection procedure, described crop management by combining different aspects into few quantities and highlighted its critical environmental issues. The work represents a starting point for improving cropping system management in the study area; the same procedure could be re-applied if data about improved management scenarios were available.     

Effects of input management and crop diversity on non-renewable energy use efficiency of cropping systems in the Canadian Prairie

Although producers’ prime objective may be to increase net returns, many are also interested in conserving and enhancing the quality the soil, water and air resources through adopting more environmentally friendly production practices. This study compared non-renewable energy inputs, energy output, and energy use efficiency of nine dryland cropping systems comprised of a factorial combination of three methods of input management [high (HIGH), i.e., conventional tillage plus full recommended rates of fertilizer and pesticides; reduced (RED), i.e., conservation tillage plus reduced rates of fertilizer and pesticides; and organic (ORG), i.e., conventional tillage plus N-fixing legumes and non-chemical means of weed and pest control]; and three crop rotation systems with varying levels of cropping diversity [a fallow-based rotation with low crop diversity (LOW); a diversified rotation using annual cereal, oilseed and pulse grains (DAG); and a diversified rotation using annual grains and perennial forages (DAP)]. The study was conducted over the 1996–2007 period on a Dark Brown Chernozemic soil (Typic Boroll) in the Canadian Prairies. As expected, total direct plus indirect energy input was the highest for the HIGH and RED input treatments (3773 MJ ha^?1 year^?1), and 50% less for ORG management. Most of the energy savings came from the non-use of inorganic fertilizers and pesticides in the ORG management treatments. Further, total energy use was the highest for the DAG treatments (3572 MJ ha^?1 year^?1), and similar but about 18% lower for the DAP and LOW crop diversity treatments compared to DAG. Thus, overall, the HIGH/DAG and RED/DAG systems had the highest energy requirements (4409 MJ ha^?1 year^?1) and ORG/DAP had the lowest (1806 MJ ha^?1 year^?1). Energy output (calorimetric energy content) was typically the highest for the HIGH input treatments (26,541 MJ ha^?1 year^?1), was about 4% less with RED, and 37% less with ORG management. The latter reflected the lower crop yields obtained with organic management. Similarly, energy output was the highest for the DAP treatments (25,008 MJ ha^?1 year^?1), about 5% less for DAG, and 20% less for the LOW crop diversity treatments. The higher energy output with the DAP treatments largely reflected that the entire harvested biomass of the forage crops was included in energy output, while for grain crops only the seed was included. The straw and crop residues from annual crops were returned to the land to protect the soil from erosion and to maintain soil organic matter as this is the recommended practice in this semi-arid region. In contrast to energy output and to net energy produced, energy use efficiency (measured as yield of grain plus forage produced per unit of energy input or as energy output/energy input ratio) was the highest for the ORG input treatments (497 kg of harvested production GJ^?1 of energy input, and an energy output/energy input ratio of 8.8). We obtained lower, but generally similar energy use efficiency for the HIGH and RED input treatments (392 kg GJ^?1 and ratio of 7.1). Thus, overall, ORG/DAP was the most energy efficient cropping system, while RED/LOW and RED/DAG generally ranked the lowest in energy use efficiency. Our findings support the current movement of producers toward ORG management as a means of reducing the reliance on non-renewable energy inputs and improving overall energy use efficiency of their cropping systems. Our results also suggest that moving away from traditional monoculture cereal rotations that employ frequent summer fallowing, toward extended and diversified crop rotations that use reduced tillage methods, although resulting in an increase in energy output, will not significantly reduce the overall reliance on non-renewable energy inputs, nor enhance energy use efficiency, unless perennial legume forages and/or legume grain crops are included in the cropping mix.     

Radiation interception and radiation use efficiency of potato affected by different N fertigation and irrigation regimes

Three years of field experiments were carried out to explore the response of potato dry matter production, accumulated intercepted photosynthetic active radiation (Aipar) and radiation use efficiency (RUE) to five N levels providing 0, 60, 100, 140 and 180 kg N ha⁻¹ and three drip irrigation strategies, which were full, deficit and none irrigation. Results showed that, irrespective of years, dry matter production and Aipar were increased by prolonged N fertigation, even though N fertigation was carried out from middle to late growing season. The highest total and tuber dry matter and accumulated radiation interception in all three years were obtained when potatoes were provided with 180 kg N ha⁻¹. RUE on the other hand was not affected by N regime. Thus, increases in total dry matter production with increasing N levels were essentially caused by higher Aipar. The strongest response to N fertilization occurred when most N was applied early in the growing season and the latest N fertilization should be applied no later than 41–50 days after emergence. Deficit irrigation, which received ca.70% of irrigation applied to full irrigation, did not reduce radiation interception and radiation use efficiency.     

White lupine as a beneficial crop in Southern Europe. II. Nitrogen recovery in a legume–oat rotation and a continuous oat–oat

One experiment lasting for two years was carried out at Pegões (central Portugal) to estimate the impact of mature white lupine residue (Lupinus albus L.) on yield of fodder oat (Avena sativa L. cv. Sta. Eulalia) as the next crop in rotation, comparing with the continuous cultivation of cereal, under two tillage practices (conventional tillage and no-till) and fertilized with five mineral nitrogen (N) rates, with three replicates. Oat as a first crop in the rotation provided more N to the agro-ecosystem (63 kg N ha⁻¹) than did lupine (30–59 kg N ha⁻¹). This was at a cost of 100 kg of mineral N ha⁻¹, whereas lupine was grown without addition of N. A positive response of oat as a second crop was obtained per kg of lupine-N added to the system when compared with the continuous oat–oat. The cereal also responded positively to mineral N in the legume amended soil in contrast with the oat–oat sequence where no response was observed, partly due to the fast mineralization rate of lupine residue and a greater soil N immobilization in the continuous oat system. Each kg N ha⁻¹ added to the soil through the application of 73 kg DM ha⁻¹ mature lupine residue (above- and belowground material) increased by 72 kg DM ha⁻¹ the oat biomass produced as the second crop in rotation when 150 kg mineral N ha⁻¹ were split in the season, independent of tillage practice. Mature legume residue conserved in the no-tilled soil depressed the yield of succeeding cereal but less than the continuous oat–oat for both tillage practices, where the application of mineral N did not improve the crop response.     

Nitrogen fertilisation of irrigated maize under Mediterranean conditions

Nitrogen fertilisation of maize (Zea mays L.) has become an important economic and environmental issue, especially in high-yielding irrigated Mediterranean areas. Producers have traditionally applied more N fertiliser than required and, as a result, some environmental problems have appeared in recent decades. A 4-year study (2002–2005) was conducted and six N rates (0, 100, 150, 200, 250 and 300 kg N ha^?1 year^?1) were compared. Before planting 50 kg N ha^?1 were applied. The rest of the N was applied in two sidedresses, the first at V3–V4 developing stage and the second at V5–V6. Yield, biomass, grain N uptake, plant N uptake and SPAD-units were greatly influenced by both N fertilisation rate and soil NO₃^?-N content before planting and fertilising [Nini (0–90 cm)]. At the beginning of the experiment, Nini was very high (290 kg NO₃^?-N ha^?1) and there was therefore no yield response to N fertilisation in 2002. In 2003, 2004 and 2005, maximum grain yields were achieved with 96, 153 and 159 kg N ha^?1, respectively. Results showed that N fertilisation recommendations based only on plant N uptake were not correct and that Nini should always be taken into account. On the other hand, the minimum amount of N available for the crop [N applied with fertilisation plus Nini (0–90 cm)] necessary to achieve maximum grain yields was 258 kg N ha^?1. This value was similar to plant N uptake, suggesting that available N was able to predict N maize requirements and could be an interesting tool for improving maize N fertilisation.