Explore the vast range of titles available.

Limited nutrient availability is one of the major challenges in organic farming. Little is known about nutrient budgets of organic farms, the underlying factors or effects on soil fertility. We therefore assessed farm gate nutrient budgets for nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg) and sulfur (S) of 20 organic farms in Germany and analyzed their soil nutri-ent status. In average, the budgets showed a surplus of N (19 kg ha−1), K (5 kg ha−1), S (12 kg ha−1), and Mg (7 kg ha−1), and a deficit of P (−3 kg ha−1). There was, however, high variability between farms (e.g. standard deviation up to ± 36 kg N ha−1), which was mainly explained by different degrees of reliance on biological N fixation (BNF) as N source. When farms obtained more than 60% of their N input through BNF, they had deficits of P (mean −8 kg P ha−1) and K (mean −18 kg K ha−1). Nutrient status of most soils was within the ad-vised corridor, but for P, K and Mg, 10–15% of fields were lower and 45–63% were higher than advised. Extractable soil nutrient contents did not correlate with the nutrient budgets, inputs or outputs. Only extractable soil P increased with increasing P inputs and outputs. Fur-thermore, a decrease in extractable soil P was detected with a prolonged history of organic farming, indicating a risk of soil P mining in organic farming systems. In conclusion, the study revealed nutrient imbalances in organic farming and pointed to P and K scarcity as a major challenge for organic farms with high reliance on BNF in the long term.

The continuous rise in the global demand for palm oil has resulted in large-scale expansion of industrial oil palm plantations-largely at the expense of primary and secondary forests. The potentially negative environmental impacts of these conversions have given rise to closer scrutiny. However, empirical data on the effects of conversion of forests to industrial oil palm plantations on soil organic carbon (SOC) stocks is scarce and patchy. We evaluated the changes in SOC stocks after conversion of tropical forest into oil palm plantations over the first and second rotation period in Sarawak, Malaysian Borneo. Soil samples were collected from three age classes of oil palm plantations converted from forest (49, 39 and 29 years ago respectively) with three replicate sites and four adjacent primary forest sites as reference. In each site under oil palm, the three management zones, namely weeded circle (WC), frond stacks (FS), and between palm (BP), were sampled separately. All soil samples were collected from five soil layers (0-5, 5-15, 15-30, 30-50 and 50-70 cm). Samples were analysed for SOC concentration, soil bulk density, pH and soil texture. Results showed SOC stocks declined by 42%, 24% and 18% after 29, 39 and 49 years of conversion respectively. Significant differences in SOC stocks were found among different management zones in the oil palm plantations, and the trend was similar for all age classes: FS > WC > BP, demonstrating the necessity of considering within-plantation variability when assessing soil C stocks. The largest differences between SOC stocks of the reference forest and converted plantations were found in the topsoil (0-15 cm depth) but differences were also found in the subsoil (>30 cm). Our results will contribute towards future modelling and life cycle accounting to calculate the carbon debt from the conversion of forest to oil palm plantations.

A continuous rise in the global demand for palm oil has resulted in the large‐scale expansion of oil palm plantations and generated environmental controversy. Efforts to increase the sustainability of oil palm cultivation include the recycling of oil mill and pruning residues in the field, but this may increase soil methane (CH4) emissions. This study reports the results of yearlong field‐based measurements of soil nitrous oxide (N2O) and CH4 emissions from commercial plantations in North Sumatra, Indonesia. One experiment investigated the effects of soil‐water saturation on N2O and CH4 emissions from inorganic fertilizers and organic amendments by simulating 25 mm rainfall per day for 21 days. Three additional experiments focused on emissions from (a) inorganic fertilizer (urea), (b) combination of enriched mulch with urea and (c) organic amendments (empty fruit bunches, enriched mulch and pruned oil palm fronds) applied in different doses and spatial layouts (placed in inter‐row zones, piles, patches or bands) for a full year. The higher dose of urea led to a significantly higher N2O emissions with the emission factors ranging from 2.4% to 2.7% in the long‐term experiment, which is considerably higher than the IPCC standard of 1%. Organic amendments were a significant source of both N2O and CH4 emissions, but N2O emissions from organic amendments were 66%–86% lower than those from inorganic fertilizers. Organic amendments applied in piles emitted 63% and 71% more N2O and CH4, respectively, than when spread out. With twice the dose of organic amendments, cumulative emissions were up to three times greater. The (simulated) rainwater experiment showed that the increase in precipitation led to a significant increase in N2O emissions significantly, suggesting that the time of fertilization is a critical management option for reducing emissions. The results from this study could therefore help guide residue and nutrient management practices to reduce emissions while ensuring better nutrient recycling for sustainable oil palm production systems. In an effort to increase the environmental sustainability of oil palm cultivation, gas samples were collected from three yearlong experiments that focused on N2O and CH4 emissions from urea, combination of enriched mulch with urea, and organic amendments applied in different doses and spatial layouts from commercial plantations in North Sumatra, Indonesia. The results showed that the combination of inorganic fertilizers and organic amendments could reduce N2O and CH4 emissions by a greater extent than the urea or organic amendments applied individually. These results could therefore help guide residue and nutrient management practices to reduce emissions for sustainable oil palm production systems.

Biostimulants (Bio-effectors, BEs) comprise plant growth-promoting microorganisms and active natural substances that promote plant nutrient-acquisition, stress resilience, growth, crop quality and yield. Unfortunately, the effectiveness of BEs, particularly under field conditions, appears highly variable and poorly quantified. Using random model meta-analyses tools, we summarize the effects of 107 BE treatments on the performance of major crops, mainly conducted within the EU-funded project BIOFECTOR with a focus on phosphorus (P) nutrition, over five years. Our analyses comprised 94 controlled pot and 47 field experiments under different geoclimatic conditions, with variable stress levels across European countries and Israel. The results show an average growth/yield increase by 9.3% (n=945), with substantial differences between crops (tomato > maize > wheat) and growth conditions (controlled nursery + field (Seed germination and nursery under controlled conditions and young plants transplanted to the field) > controlled > field). Average crop growth responses were independent of BE type, P fertilizer type, soil pH and plant-available soil P (water-P, Olsen-P or Calcium acetate lactate-P). BE effectiveness profited from manure and other organic fertilizers, increasing soil pH and presence of abiotic stresses (cold, drought/heat or salinity). Systematic meta-studies based on published literature commonly face the inherent problem of publication bias where the most suspected form is the selective publication of statistically significant results. In this meta-analysis, however, the results obtained from all experiments within the project are included. Therefore, it is free of publication bias. In contrast to reviews of published literature, our unique study design is based on a common standardized protocol which applies to all experiments conducted within the project to reduce sources of variability. Based on data of crop growth, yield and P acquisition, we conclude that application of BEs can save fertilizer resources in the future, but the efficiency of BE application depends on cropping systems and environments.

PurposeLife cycle assessments (LCAs) that attempt to provide advice on treatment options for phosphorus (P) containing organic waste products encounter problems related to the quantification of mineral P fertilizer substitution, P loss and crop P uptake after land application. The purpose of this study was to develop a relatively easy to use life cycle inventory model, known as PLCI, that could be used to estimate these values.MethodsA life cycle inventory model for P was developed, which estimates the effect of an application of organic waste followed by ordinary fertilizer management in the modeling period. This was compared with a simulation without the initial waste application. The difference in mineral P fertilizer application (substitution), P loss and crop P uptake was then calculated and expressed as a proportion of the amount of waste applied. As an example, the effect of an initial application of mineral fertilizer, sewage sludge and ash on two farm types was simulated. These results were applied in an LCA case study of different sewage sludge treatment options.Results and discussionFarm type influenced the P fertilizer substitution, loss and crop uptake factors. The application on an arable farm showed a substitution of 28 to 31%, relatively low P loss and a large spread in crop P uptake for the different P sources, compared with the pig farm. Application on a pig farm showed no mineral P substitution. For substitution, mineral fertilizer outperformed waste product fertilizer with a short modeling period, due to higher immediate P availability, which was not the case with a long period. The LCA case study showed that the P substitution factor had an influence on the environmental impact categories climate change and depletion of reserve-based abiotic resources while the P loss factor influenced freshwater eutrophication. Application of the P loss and substitution factors generated from the PLCI model resulted in higher environmental burdens and lower savings than using conventional factors.ConclusionsThe soil P status mainly affected P substitution and loss, with the fertilizer type only having a small influence when soils had a low P status. The PLCI model can facilitate more coherent and rigorous estimates of P substitution and loss to be used in LCA studies involving application of waste products on agricultural land. This is important since P substitution and loss can have an important influence on impact categories, such as freshwater eutrophication and resource depletion.

Phosphorus (P) is critical for food production. However, it has been managed unsustainably for decades and geopolitical challenges complicate its availability. While accessible P-rock deposits are linearly exploited, excessive fertilization practices lead to P loss from land to water, and thus, eutrophication. The release of legacy P from sediments to the water column, i.e. internal P loading, sustains global eutrophication issues. Sediment removal and its subsequent reuse as soil amendment can simultaneously lower internal P loadings and create a new P resource. However, the plant bioavailability of sedimentary P, especially Fe-P, is rather controversial. In this study, the direct P fertilizer effect of fresh lake sediment, lake sediment after Fe-P removal, amorphous Fe-P, and the reduced Fe-P mineral vivianite on barley was investigated and compared to the conventional mineral P fertilizer triple superphosphate (TSP). Fresh sediment, amorphous Fe-P, and vivianite fertilization significantly increased biomass and P uptake compared to the 0-control, while the Fe-P removal from the sediment reduced both effects. The P use efficiency was generally lower than for TSP and decreased in the order amorphous Fe-P > fresh sediment > vivianite > sediment after Fe-P removal. In a parallel soil incubation without barley growth P diffusion from the tested alternative substrates was not observed. We conclude that fresh lake sediment has P fertilizer potential with amorphous Fe-P as a significant contributor. Further, fertilization with fresh sediment and Fe-P can increase soil adsorptive capacities potentially reducing leaching but also creating dependency of plant P bioavailability on plant-soil interactive mechanisms.

Understanding the mobilization processes of phosphorus (P) in the plow layer are essential to quantify potential P losses and suggest management strategies to reduce P losses. This study is aimed at examining nonequilibrium exchange dynamics on the mobilization of slurry‐amended Br−, and dissolved and particulate P in slurry‐injected soils. We compared leaching from intact soil columns (20 cm diam., 20 cm high) under unsaturated flow (suction at the lower boundary of 5 hPa) subjected to continuous irrigation at 2 mm hr−1, and intermittent irrigation at 2 mm hr−1 and 10 mm hr−1 to with interruptions of 10 h duration simulate periodic precipitation events. Suction was increased to 20 hPa during interruptions to allow drainage of the largest pores. Irrigation interruptions induced fluctuations in leaching of nonreactive tracers, particles, and particulate P indicating nonequilibrium transport. A nonreactive tracer, 3H2O, applied with irrigation water, diffused from mobile to less mobile pore regions during interruptions, leading to a lower mass recovery during low‐intermittent (76.4%) compared with continuous irrigation (86.6%). In contrast, mass recovery of slurry‐injected Br− increased as Br− diffused from less mobile to mobile pore regions during low‐intermittent (53%–64%) compared with continuous irrigation (42%–47%). Despite high fluctuations during the leaching of particles and particulate P during low‐intermittent irrigation, accumulated values did not differ from continuous irrigation. Increased preferential flow during high‐intermittent irrigation lowered the mass exchange between pore regions of nonreactive tracers, particles, and particulate P compared with low‐intermittent irrigation. The leaching of dissolved inorganic and organic P was low during all of the experiments and scarcely affected by the irrigation regime. These results highlight that nonequilibrium exchange dynamics are important when evaluating processes affecting mobilization and transport in structured soils. Leaching experiments, including cycles of irrigation interruptions and gravitational drainage, thus, adds significantly to the understanding and interpretation of processes affecting mobilization and transport under natural conditions. Key Points Intermittent precipitation increased mobilization of nonreactive tracers Intermittent precipitation did not affect mobilization of phosphorus forms Mobilization of particles proved to be affected by different flow regimes

Abstract Background: Variations in sugar yield due to genotypic qualities of feedstock are largely undescribed for pilot-scale ethanol processing. Our objectives were to compare glucose and xylose yield (conversion and total sugar yield) from straw of five winter wheat cultivars at three enzyme loadings (2.5, 5 and 10 FPU g-1 dm pretreated straw) and to compare particle size distribution of cultivars after pilot-scale hydrothermal pretreatment. Results: Significant interactions between enzyme loading and cultivars show that breeding for cultivars with high sugar yields under modest enzyme loading could be warranted. At an enzyme loading of 5 FPU g-1 dm pretreated straw, a significant difference in sugar yields of 17% was found between the highest and lowest yielding cultivars. Sugar yield from separately hydrolyzed particle-size fractions of each cultivar showed that finer particles had 11% to 21% higher yields than coarse particles. The amount of coarse particles from the cultivar with lowest sugar yield was negatively correlated with sugar conversion. Conclusions: We conclude that genetic differences in sugar yield and response to enzyme loading exist for wheat straw at pilot scale, depending on differences in removal of hemicellulose, accumulation of ash and particle-size distribution introduced by the pretreatment.

Aims The aim of this study was to evaluate the effects of long-term mineral and organic fertilisation on crop performance and soil fertility. Methods The Long-Term Nutrient Depletion Trial (Denmark) was used to analyse changes in concentrations of Olsen-P, exchangeable potassium (K) and soil carbon (C). Yield responses (2010–2016) were evaluated making use of an early-season temperature model, fertilisation practices were evaluated by nutrient budgets, and nitrogen use efficiency by calculation of apparent recovery (ANR) in subplots receiving mineral N. Results Olsen-P (r 2  = 0.68, P  < 0.001) and exchangeable K (r 2  = 0.86, P  < 0.001) were correlated with the nutrient budgets. Soil C concentrations increased from 10.0 g kg −1 (1995) to between 11.1–14.6 g kg −1 (2016), with the greatest accumulation under slurry applications ( P  < 0.05, equalling 17–47% retention of slurry-C inputs). Relative yield responses of spring barley were associated with early season cold stress, but the model was not applicable to other crops. Increases of ANR in response to long-term phosphorus (P) applications were not significant. Conclusions Balanced fertilisation is an effective way to maintain nutrient availability, and to ensure high and stable crop productivity and efficient use of nutrients. Direct C inputs from animal slurry are a major driver for increases of soil C concentrations.

Background and Aims A number of root and root hair traits have been proposed as important for acquisition of P. However, it remains unknown whether these traits are most important in determining macro- and micronutrient uptake at low soil fertility. This study investigated the variations in root and root hair traits among spring wheat genotypes and examined which root and root hair traits are most important for high uptake of macro- and micronutrients. Methods Six spring wheat genotypes were grown in a soil with low nutrient availability. The root and root hair traits as well as the content of macro- and micronutrients were identified. Results A significant genetic variability in root and root hair traits was found. High root growth vigour and long and dense root hairs enhanced uptake of macro- and micronutrients under low soil nutrient availability. Root growth vigour, however, was a better predictor of early nutrient acquisition than root hair length and density. Conclusions Selection and breeding for high root growth vigour and long and dense root hairs is a promising strategy to ensure efficient acquisition of both macro- and micronutrients in the early establishment of spring wheat in nutrient-limited soil and low nutrient input cropping systems.