Vegetable Crop Residues Research Articles

Organic vegetable crop residue decomposition in soils

Soil organic carbon (SOC) is an important property that influences soil chemical, physical, and biochemical processes and is a key indicator of soil health. Rapid decomposition of crop residues incorporated into soil reduces the potential of carbon (C) sequestration in the Southeast United States where SOC is very low rending residue management very critical. We investigated the C contents and the decomposition of cultivars of popular organic vegetable crops [southern pea (Vigna unguiculata), squash (Cucurbita maxima), sweet potato [Ipomoea batatas (L.) Lam] and tomato (Solanum lycopersicum)] in two soils under laboratory conditions. The C contents of the crop residues were determined by using a wet chemistry method. A non-linear regression model was used to determine the potentially mineralizable C (C0) and the first-order rate constant (k) of the decomposition following incubation of soils treated with the vegetable crop residues for 30 days at room temperature. The average C contents varied between 304 and 437 g kg−1. On average, the sweet potato cultivars showed a greater C0 (19.4 g C kg−1) in Cecil soil than in Hartsells soil while tomato cultivars showed the least C0 (15.9 g C kg−1) in Hartsells soil. The k values showed that squash cultivars decomposed faster (0.106 day-1) than any other crop, whereas southern pea cultivars decomposed the least in Cecil and Hartsells soils. Strong relationships between C0, k, and C/N were established. Organic growers are environmentally conscious framers who wants to mitigate the greenhouse effect and global warming by adopting cropping systems that would sequester more C into the soil. Thus, identifying and selecting vegetable crop cultivars that would incorporate more C in soil is of a great interest to them. These findings have potentials of guiding organic growers in selecting crop cultivars that would increase OC sequestration in soils.

Application of Anaerobic Digestion Model No. 1 for modeling anaerobic digestion of vegetable crop residues: Fractionation of crystalline cellulose

Abstract Crystalline cellulose is fully resistant during anaerobic digestion (AD), which brings uncertainty to the use of mathematical models to simulate the dynamic AD process of lignocellulosic waste. In present study, a modified mathematical model, with crystalline cellulose as the primary consideration, was established based on Anaerobic Digestion Model No.1 to simulate the anaerobic bioconversion of vegetable crop residues (VCR) under mesophilic condition. In this model, VCR was divided into inert fraction (contained lignin and crystalline cellulose), as well as biodegradation parts of slowly hydrolysis fraction (SHF, contained hemicellulose and amorphous cellulose), and readily hydrolysis fraction (RHF, contained other organic components in the VCR). Data from a series of batch experiments have been used for the calibration and verification of this model. As a result, the calibrated model was found to match reasonably well the methane production data of three different VCRs, which implies that it was feasible to fractioned VCR into three fractions (SHF, RHF and inert part), and the operation that classified crystalline cellulose into the inert part, while regarded amorphous cellulose as SHF was appropriate. In order to be suitable for simulating the AD process of more other types of lignocellulosic waste, the model needs further modification and inspection. • A novel feedstock characterization method was proposed to modify ADM1. • Methane production of three vegetable crop residues were simulated by ADM1. • The interaction of several sensitive parameters was evaluated.

Burial and Compaction of Sandy Soils to Prevent Emergence of Adult Stable Fly (Diptera: Muscidae) at the Soil Surface.

Stable fly (Stomoxys calcitrans L.) remain a significant pest affecting livestock and rural communities on the Swan Coastal Plain around Perth, Western Australia. Vegetable crop residues remaining after harvest enable stable fly development. Left untreated they can produce from several hundred to >1,000 stable fly/m2 of post-harvest residues. We studied the effect of burial and compaction of sandy soils on adult emergence of stable fly and house fly (Musca domestica L.) (Diptera: Muscidae). Adults of both fly species can move up through 50 cm of loose, dry sand, however at depths greater than 60 cm, emergence rapidly declines with <5% of adults surviving under 100 cm of soil. Burial of stable fly larvae and pupae under 15 cm of soil followed by compaction using a static weight dramatically reduced adult emergence. Moist soil compacted at ≥3 t/m2 completely prevented stable fly emergence whereas house fly emergence was not affected. One t/m2 of compaction resulted in <5% emergence of stable fly buried as pupae. Soil that was easily compactible (i.e., high silt, fine sand and clay content) reduced stable fly emergence more than soil with more coarse sand and low clay content. This study demonstrates the potential for a novel and chemical-free option for controlling stable fly development from vegetable crop post-harvest residue. Field trials are needed to confirm that burial and compaction of vegetable post-harvest residues using agricultural machinery can dramatically reduce the subsequent emergence of adult stable fly on a large scale.

Effect of Crop Residue Removal and Straw Addition on Nitrous Oxide Emissions from a Horticulturally Used Soil in South Germany

Core Ideas The main aim was to reduce N2O emission through crop residue removal or N immobilization through straw addition in fall. Annual N2O emission was reduced by 74% through removal of vegetable crop residues in fall. N2O emission in the removal treatment was as low as in the unfertilized control. Straw addition in autumn failed to reduce N2O emission (p = 0.057). Vegetable production, such as cauliflower (Brassica oleracea var. botrytis L.) or broccoli (Brassica oleracea var. italica P.), is often associated with high N surpluses, posing the risk for substantial N losses. Straw addition in autumn to immobilize surplus N over winter or removal of vegetable crop residues were shown to reduce nitrate leaching efficiently. However, the effect of these management measures on the release of nitrous oxide (N2O) is still unclear. We determined N2O fluxes from a vegetable field with a silty texture in southern Germany over 2 yr in the following treatments: no N fertilization (−N), conventional N fertilization without (CON), and N fertilization with crop residue removal (−CR) or straw addition (+S). Marketable fresh matter yields and N uptake showed only minor differences among all N‐fertilized treatments. Enhanced N2O fluxes occurred over a period of nearly 6 mo in the first year in autumn and winter after crop residue incorporation. Positive correlations between N2O fluxes and driving soil variables suggested denitrification as the major N2O source. Cumulative N2O emission ranged between 5.2 (−CR) and 37.2 kg N2O–N ha−1 yr−1 (CON). Crop residue removal reduced N2O emission in CON very efficiently by 74%. Straw addition reduced N2O emission in only 1 yr. The N2O emission factors were 4.3, 1.9, and 3.1 for CON, −CR, and +S, respectively. The high N2O reduction by crop residue removal seems to be promising in terms of mitigation, but long‐term effects, such as missing humus reproduction, should be considered in future studies.

Evaluation of Biochemical Methane Potential and Kinetics on the Anaerobic Digestion of Vegetable Crop Residues

There is a lack of literature reporting the measurement and prediction of biochemical methane potential (BMP) of vegetable crop residues (VCRs) and similarly, the kinetic assessment on the anaerobic digestion process of VCR is rarely investigated. In this paper, the BMP tests of five different vegetable (snap bean, capsicum, cucumber, eggplant, and tomato) crop residues were conducted at feed to inoculum ratio (F/I) of 2.0 under mesophilic (36 ± 1 °C) conditions. A series of single-variable and multiple-variable regression models were built based on organic components (hemicellulose, cellulose, lignin, total fat, total sugar, and crude protein) for BMP prediction. Three kinetic models, including the first-order kinetic model, the Chen and Hashimoto model, and the modified Gompertz model, were used to simulate the methane yield results of VCR and obtain valuable model parameters simultaneously. As a result, the BMPs and volatile solids (VS) degradation degree of different VCRs were respectively in the range of 94.2–146.8 mL g−1 VS and 40.4–49.9%; the regression prediction models with variables lignin (R2 = 0.704, p = 0.076), variables crude protein and lignin (R2 = 0.976, p = 0.048), and variables total fat, hemicellulose, and lignin (R2 = 0.999, p = 0.027) showed the best performance on BMP prediction among the single-factor, two-factor, and three-factor models, respectively. In addition, compared to the other two kinetic models, the modified Gompertz model could be excellently fitted (R2 = 0.986–0.998) to the results of BMP experiment, verification deviations within 0.3%.

Potential benefits of near critical and supercritical pre-treatment of lignocellulosic biomass towards anaerobic digestion.

Vegetable crop residues, such as sugarcane bagasse (SCB), despite their limited biodegradability, are potential materials for anaerobic processes because of their low cost, high availability, and sugar content. The difficulty of biodegrading this type of material is primarily related to its chemical composition and to the complex interactions between its compounds (cellulose, hemicelluloses, and lignin). Thus, the following supercritical and near critical carbon dioxide (CO2) pre-treatments were evaluated with and without the addition of sodium hydroxide (NaOH): (i) 40°C/70 kgf·cm-2; (ii) 60°C/200 kgf·cm-2; and (iii) 80°C/200 kgf·cm-2, aiming to enhance the anaerobic biodegradability of SCB. The methanogenic production of SCB increased in all cases in which the material was pre-treated, except the case in which NaOH was used together with a high temperature. The condition using CO2 at 60°C/200 kgf·cm-2 was highlighted with a lignin removal of 8.07% and an accumulated methane production of 0.6498 ± 0.014 LN (273.15K, 1.01325 × 105 Pa), 23.4% higher than the value obtained with the untreated material. This condition also showed the highest net energy at the energy balance that was calculated for comparison with the tested conditions. The results showed that pre-treatments with near critical and supercritical fluids have the potential to reduce structural obstacles of lignocellulosic materials and to enhance their anaerobic biodegradability.

Substrates across horticultural and livestock industries that support the development of stable fly, Stomoxys calcitrans (Diptera: Muscidae)

AbstractThis study examined a multitude of potential substrates across horticultural and livestock industries that supported the development of the stable fly, Stomoxys calcitrans (Linneaus) (1081 samples from over 100 properties (2010–2016)). Stable fly developed in high numbers from vegetable crop residues left after harvest, notably celery and leeks as well as several brassica crops, lettuce and silverbeet. Unmarketable vegetables (reject produce) and processing waste provided another source of stable fly development, in particular from carrot production (green tops and processing washings) as well as beetroot and daikon leaves, reject zucchinis, rockmelons, eggplants, turnips and squashes. Reject produce from mostly solanaceous plants either did not support any or rarely supported the development of adult stable fly. Reject vegetable produce fed to livestock presented a source for stable fly to develop in the vegetable/manure mix, especially from carrots and corn cobs. Large accumulations of cattle dung in feedlot situations, hay feeding out sites, wet grain feed and exposed silage produced the highest numbers of stable fly from livestock industries. Cattle dung from rangeland pastures, pig manure and horse manure rarely if ever supported the development of stable fly. Only cattle dung that had aged or pig manure that had been mixed with straw and left to age allowed for any stable fly development. Miscellaneous sources of stable fly development include rotting lawn clippings, rotting weeds, ageing olive pressing residue, and to a lesser extent, rotting wild melons and seaweed.

Co-ensiling, co-composting and anaerobic co-digestion of vegetable crop residues: Product stability and effect on soil carbon and nitrogen dynamics

Nitrogen (N)-rich vegetable crop residues left in the field may result in a high risk for N losses during autumn. Removal and conservation of these residues followed by reuse in the field could contribute to improved recycling of nutrients, but some form of processing is required to allow storage before re-application. We have compared co-ensiling, co-composting and anaerobic co-digestion as conservation and valorization options for fresh crop residues. We studied (1) the product quality and stability and (2) the short-term effects of application of these silages, composts and digestates on soil C and N mineralization and N2O emissions. Ensiling resulted in highly biodegradable products with a low pH (4.2-5.2) and more NH4+-N compared to composts. Consequently, soil incorporation of silages resulted in higher net C mineralization (up to 47% after 82days) and microbial biomass C (up to 93μgCg−1 soil after six weeks), and temporary N immobilization (up to 42mgkg−1 soil). Digestates and composts led to lower C mineralization rates (between 2 and 27%) and microbial biomass C (max. 51μgCg−1 soil) and no net N immobilization nor mineralization. Application of digestates resulted in high mineral N contents (47–192mgkg−1 soil) and a decrease of the soil pH. In all three treatments, short-term N2O losses after soil application were very small (<0.11kgNha−1 after 12days). Growers can choose the most appropriate treatment option and application moment and location, depending on the local soil and crop requirements and the on-farm facilities. Furthermore, we conclude that the parameters biodegradation potential (based on the biochemical composition) and oxygen uptake rate have potential as less time-consuming proxies for C mineralization to assess the product stability.

Emissions of nitrous oxide and ammonia after cauliflower harvest are influenced by soil type and crop residue management

The decomposition of vegetable crop residues, e.g. from Brassica species, can cause substantial nitrous oxide (N2O) and ammonia (NH3) emissions due to their high nutrient and water contents. One promising approach to reduce these harmful emissions is optimizing post-harvest crop residue management. So far published results on the effects of different crop residue placement techniques on N2O and NH3 emissions do not give a consistent picture. One of the key issues is the diverse experimental conditions, in particular with respect to soil characteristics. Therefore, we studied the effects of cauliflower residue management, i.e. no residues (control), surface application (mulch), incorporation by mixing (mix), incorporation by ploughing (plough), on N2O and NH3 emissions in a 7.5-months field study, using a unique open-air facility featuring three different soils with contrasting soil texture (loamy sand, silt loam, sandy clay loam). Cauliflower residues caused the highest N2O emissions after ploughing (2.3–3.4 kg N2O–N ha−1, 1.5–2.2 % of residue-N), irrespective of the soil type. In contrast, ammonia emissions were only affected by the residue placement technique in loamy sand, which exhibited the highest emissions in the mulch treatment (1.9 kg NH3–N ha−1, 1.2 % of residue-N). In conclusion, under the given conditions incorporating crop residues by ploughing appears to produce the highest N2O emissions in a range of soils, whereas surface application may primarily increase NH3 emissions in coarse-textured soils.

Effect of the nitrification inhibitor (DMPP) on soil nitrous oxide emissions and yield in a lettuce crop in Queensland, Australia

The use of nitrification inhibitors, in combination with ammonium based fertilisers, has been promoted recently as an effective method to reduce nitrous oxide (N2O) emissions from fertilised agricultural fields, whilst increasing yield and nitrogen use efficiency. However, to date no data is available on the use of nitrification inhibitors in sub-tropical vegetable systems. A field experiment investigated the effect of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) on N2O emissions and yield from lettuce production in sub-tropical Australia. Soil N2O fluxes were monitored continuously over 120 days with a fully automated system. Measurements were taken from three subplots for each treatment within a randomized complete blocks design. Cumulative N2O emissions over the 120 day observation period amounted to 191, 93 and 46 g-N ha-1 in the conventional fertiliser (CONV), the DMPP treatment and the zero fertiliser (0N) respectively. Consequently, the use of DMPP decreased seasonal N2O emissions by more than 50%, but had no significant impact on lettuce yield. The temporal variation of N2O fluxes showed only low emissions over the lettuce cropping period in all treatments, but significantly elevated emissions were observed in the CONV fertilized and DMPP treatment postharvest, following lettuce residues being incorporated into the soil. This study highlights that DMPP can substantially reduce N2O emissions from vegetable cropping systems. It also emphasizes that N input from vegetable crop residues incorporated into the soil after harvest can lead to substantially elevated N2O emission. Hence, in such systems post-harvest emissions need to be in the centre of attention for developing N2O mitigation strategies.

Effect of ensilaged vegetable crop residue amendments on soil carbon and nitrogen dynamics

Vegetable crop residues aid in maintaining soil quality and fertility, but pose a high risk of N-losses during autumn. Removal and conservation of these residues followed by a timely reapplication in spring may aid in synchronizing nutrient demand and availability. Crop residues of four vegetables were co-ensilaged with maize straw in a 1:1 ratio on volume base. Silage of leek and white cabbage were incubated with soil for measuring C and N mineralization and N fertilizer replacement value (NFRV). Vegetable crop residue silage promoted microbial activity when reapplied to the soil. This led to a temporary N immobilization up to 30% of the applied N after 14 days. A limited remineralization of up to +4% took place after 115 days which was confirmed by the positive NFVR. Nitrogen (N) losses during co-ensilage of vegetable crop residues were small and may help reduce N losses in intensive vegetable crop rotations during winter.

Nitrogen cycling and management in intensive horticultural systems

Vegetables are important horticultural commodities with high farm gate values and nutritional quality. For many vegetables, growers apply large amounts of N fertilizer (>200 kg N ha−1) to increase yield and profits, but such high N fertilizer applications can pose a significant threat for N loss and environmental contamination via denitrification, volatilization, leaching, runoff, and erosion. Nitrogen losses can reduce air and water quality by contributing to greenhouse gas emissions, ground-level ozone and particulate matter production, ground and surface water contamination, and eutrophication. The processes governing N loss include a complex of biological, physical, and chemical factors, which are impacted by management practices, climatic conditions and soil properties. Therefore, we reviewed and evaluated various management practices for minimizing N loss in N-intensive vegetable production within a temperate climate. Most soil nutrient management practices have focused on reducing N loss throughout the growing season, but the risk for N loss is very high after harvesting vegetables with low N harvest indices, low C:N ratios, and high quantities of N in crop residues, such as most Brassicaoleracea L. crops. Amending soil with organic C material may present a novel strategy for reducing N losses after harvest by 37 %, compared to the typical practice of incorporating N-rich vegetable crop residues. Research must focus on testing new and innovative methods of minimizing post-harvest N loss in intensive horticulture.

Review of Alternative Management Options of Vegetable Crop Residues to Reduce Nitrate Leaching in Intensive Vegetable Rotations

Vegetable crop residues take a particular position relative to arable crops due to often large amounts of biomass with a N content up to 200 kg N ha−1 left behind on the field. An important amount of vegetable crops are harvested during late autumn and despite decreasing soil temperatures during autumn, high rates of N mineralization and nitrification still occur. Vegetable crop residues may lead to considerable N losses through leaching during winter and pose a threat to meeting water quality objectives. However, at the same time vegetable crop residues are a vital link in closing the nutrient and organic matter cycle of soils. Appropriate and sustainable management is needed to harness the full potential of vegetable crop residues. Two fundamentally different crop residue management strategies to reduce N losses during winter in intensive vegetable rotations are reviewed, namely (i) on-field management options and modifications to crop rotations and (ii) removal of crop residues, followed by a useful and profitable application.

국내 주요 시설채소 부산물의 메탄 생산 퍼텐셜

본 연구는 안성시 관내에서 발생하는 농산부산물 바이오매스 중 오이, 토마토, 파프리카 작물 잔사를 수거하여 실험에 공시하고 각 부산물의 발생특성과 메탄 생산 퍼텐셜을 조사 분석하였다. 농산부산물의 에너지 자원화 기준으로는 메탄생산량을 설정하고, 부산물별 메탄 퍼텐셜을 시험하였으며 측정된 메탄 퍼텐셜을 기초자료로 활용하여 단위면적당 바이오매스 발생량, 바이오가스 생산량 및 비료가치를 조사 분석하였다. 실험적 메탄 퍼텐셜은 농산부산물별로 <TEX>$0.170{\sim}0.354Nm^3\;kg^{-1}\;VS_{added}$</TEX>의 값을 보였으며, 그중 파프리카 열매가 가장 높은 메탄 생산 퍼텐셜을 보였으며, 오이 줄기가 가장 낮은 메탄 생산 퍼텐셜을 보였다. 시설 원예에서 기인하는 바이오매스별 메탄생산량은 줄기 부위가 잎이나 열매 부위 보다 낮은 값을 나타내는 경향을 보였다. 시설 재배지의 단위면적당 바이오매스 발생량은 오이 30.5 > 토마토 28.3 > 파프리카 <TEX>$21.5Mg\;ha^{-1}$</TEX>순 이었으며, 단위면적당 메탄생산량은 오이 782.5 > 파프리카 686.8 > 토마토 <TEX>$645.0Nm^3\;ha^{-1}$</TEX>순 이었다. Number of crop residues generated at large amount in agriculture can be utilized as substrate in methane production by anaerobic digestion. Greenhouse vegetable crop cultivation that adopting intensive agricultural system require the heating energy during winter season, meanwhile produce waste biomass source for the methane production. The purpose of this study was to investigate the methane production potential of greenhouse vegetable crop residues and to estimate material and energy yield in greenhouse system. Cucumber, tomato, and paprika as greenhouse vegetable crop were used in this study. Fallen fruit, leaf, and stem residues were collected at harvesting period from the farmhouses (Anseong, Gyeonggi, Korea) adopting an intensive greenhouse cultivation system. Also the amount of fallen vegetables and plant residues, and planting density of each vegetable crop were investigated. Chemical properties of vegetable waste biomass were determined, and theoretical methane potentials were calculated using Buswell's formula from the element analysis data. Also, BMP (Biochemical methane potential) assay was carried out for each vegetable waste biomass in mesophilic temperature (<TEX>$38^{\circ}C$</TEX>). Theoretical methane potential (<TEX>$B_{th}$</TEX>) and Ultimate methane potential (<TEX>$B_u$</TEX>) off stem, leaf, and fallen fruit in vegetable residues showed the range of <TEX>$0.352{\sim}0.485Nm^3\;kg^{-1}VS_{added}$</TEX> and <TEX>$0.136{\sim}0.354Nm^3\;kg^{-1}VS_{added}$</TEX> respectively. The biomass yields of residues of tomato, cucumber, and paprika were 28.3, 30.5, and <TEX>$21.5Mg\;ha^{-1}$</TEX> respectively. The methane yields of tomato, cucumber, and paprika residues showed 645.0, 782.5, and <TEX>$686.8Nm^3\;ha^{-1}$</TEX>. Methane yield (<TEX>$Nm^3\;ha^{-1}$</TEX>) of crop residue may be highly influenced by biomass yield which is mainly affected by planting density.

Management of stable fly and other nuisance flies breeding in rotting vegetable matter associated with horticultural crop production

Stable-fly (Stomoxys calcitrans L., Diptera: Muscidae) and other nuisance flies breeding in horticultural substrates around the Perth metropolitan area of Western Australia were investigated with regard to their larval habitats and relative abundances. Substrates were found to comprise either crop residue (i.e. stalks, leaves and fruit) left in or on the ground after harvesting, or harvested crop waste (i.e. reject produce or processing scraps dumped into open pits or fed to livestock). Stable-flies were the predominant species (>85%) developing from a wide variety of trashed vegetable crop residues. Other flies developing from these materials included house-fly, lesser house-fly, false stable-fly, blue-bodied blow-fly, black carrion-fly and flesh-flies. Stable-fly development was reduced by >90% when crop residues were sprayed with diazinon or chlorpyrifos, either prior to or immediately after incorporation of the residue into soil. Untreated crop residues yielded several hundred to >1,000 stable flies/m2 of production. Insecticides applied several weeks after crop residue incorporation into soil did not significantly reduce stable-fly emergence.

Effects of nitrogen mineralization on paddy rice yield under low nitrogen input conditions in irrigated rice-based multiple cropping with intensive cropping of vegetables in southwest China

The farm household responsibility system (FHRS) was adopted in Chinese rural areas during the economic reform in the early 1980s. Since then, many farm households have increased cropping intensity by using large quantities of nitrogen (N) fertilizers in their responsible fields to increase agricultural income. However, intensive cropping systems with low N input are still common in remote places of the southwestern region of China. Maintenance and improvement of soil quality in intensive cropping systems is critical for sustaining agricultural productivity and environmental quality for future generations. The effects of intensive cropping of vegetables on paddy rice (Oryza sativa L.) yield using small quantities of N fertilizers through N mineralization of paddy soil in irrigated rice-based multiple cropping systems were studied in 15 paddy fields in Sichuan Province, China for 3 years. Intensification of vegetable cropping with negative N balance and removal of vegetable crop residues has greatly decreased total N (TN) contents in paddy soil leading to low levels of effective cumulated soil temperature and thickness of plow layer. As a result, the N mineralization in paddy field during paddy rice growing period was decreased. In addition to the low levels of chemical fertilizer N input and residual mineral N input, the lower level of N mineralization in paddy fields and low N recovery efficiency decreased the amount of N accumulated in aboveground biomass of paddy rice at maturity, resulting in limited rice yields. The amount of mineralized N only correlated with TN (partial correlation analysis). Therefore, in paddy fields with very low N input, the N mineralization in paddy soil during the paddy rice-growing period was the major limiting factor affecting the total yield increases. In addition, a decline in soil fertility can be determined using TN as an indicator. To improve paddy rice yield and avoid soil deterioration, the development and adoption of rational soil management programs are needed. These include input of plant residues, conscientious soil tillage for the maintenance of soil temperature and thickness of the plow layer, and the split application of fertilizer for the improvement of N recovery efficiency.

Manipulating Nitrogen Release from Nitrogen‐Rich Crop Residues using Organic Wastes under Field Conditions

Following mineralization of N‐rich crop residues, large amounts of mineral N can be released into the soil. Manipulating N mineralization of crop residues may be an option to reduce NO3− in soil. The potential to manipulate the N release from vegetable crop residues by using organic wastes was tested under field conditions. At the start of the experiment, cauliflower (Brassica oleracea L. var. botrytis L.) residues (∼73 Mg fresh matter ha−1) together with an immobilizer waste (∼5 Mg C ha−1 of straw, green waste compost, sawdust, or paper sludge) were incorporated into a silt loam soil. After 154 d, a remineralizing waste (∼1 Mg C ha−1 of vinasse or dairy sludge) was incorporated. During the field experiment, the mineral N content in the soil was measured at regular time intervals, and net N release, NO3− leaching, and denitrification were simulated using a N mineralization–immobilization model coupled to a NO3− leaching model. Straw, green waste compost, and sawdust were able to immobilize between 54 and 68% of the N released by the cauliflower residues and reduced NO3− leaching by 56 to 68%. Paper sludge released an extra amount of N due to its low C/N ratio. No consistent remineralization of N could be found in any of the treatments, probably due to an unsuitable composition of the remineralizer wastes. Manipulating N release of N‐rich crop residues by using organic wastes may be a suitable method to reduce NO3− leaching; however, stimulating remineralization of immobilized N by the start of the following spring may not be easy to achieve.

Manipulating the N release from N‐rich crop residues by using organic wastes on soils with different textures

AbstractThe potential to manipulate the N release from vegetable crop residues (cauliflower, leek) by using organic wastes was tested under field conditions on three soil textures during 2 years (silt loam, sandy loam and loamy sand). During the first year, incorporation of green waste compost and sawdust did not significantly increase microbial biomass N and did not lead to a significant N immobilization of crop residue‐N. During the second year, straw did increase microbial biomass N and showed a good N immobilization potential in all textures. The largest increase in microbial biomass N and the greatest N immobilization occurred in the loamy sand soil. The texture effect was probably because of better incorporation of the crop residues and immobilizer wastes in the loamy sand soil compared with the other textures. During spring, there was no consistent remineralization of immobilized N after the addition of malting sludge or vinasses in either year. This could be a result of the limited amount of N immobilized and available for remineralization in the first year or an unsuitable composition of the remineralizer wastes.

Influence of nitrification inhibitors on soil N dynamics after incorporation of vegetable crop residues: A field study

Influence of nitrification inhibitors on soil N dynamics after incorporation of vegetable crop residues: A field study

Influence of DCD and DMPP on soil N dynamics after incorporation of vegetable crop residues

We have investigated the effect of two nitrification inhibitors, 3,4-dimethylpyrazole phosphate (DMPP) and dicyandiamide (DCD), on the accumulation of \({\text{NH}}^{{\text{ + }}}_{{\text{4}}} {\text{ - N}}\) and \({\text{NO}}^{ - }_{3} - {\text{N}}\) after incorporation of cauliflower residues in incubation experiments. Cauliflower leaves were incubated with soil and DCD or DMPP at two application rates [8.93 and 17.9 mg active component (ac) kg−1 for DCD; 0.89 and 1.79 mg ac kg−1 for DMPP]. Both doses of DCD and DMPP increased \({\text{NH}}^{ + }_{4} - {\text{N}}\) on average by 18.9 and 26.0 mg N kg−1 for DCD1 (during 30 days) and DCD2 (during 45 days), respectively, and on average by 14.4 mg N kg−1 for DMPP1 and DMPP2 during a period of at least 95 days. In DCD-treated soils, \({\text{NO}}^{{\text{ - }}}_{{\text{3}}} {\text{ - N}}\) data followed an S-shaped curve, indicating that nitrification restarted during the experiment: inhibition was on average 24% during 35 days for DCD1 and on average 45% during 49 days for DCD2. Thereafter, \({\text{NO}}^{ - }_{3} - {\text{N}}\) amount in DCD-treated soils exceeded that of the cauliflower-only treatment by 31% for DCD1 and 78% for DCD2, probably due to a nitrogen release from DCD itself and a priming effect induced by DCD. In DMPP-treated soils, \({\text{NO}}^{ - }_{3} - {\text{N}}\) data followed a linear pattern since nitrification was inhibited during the complete incubation (95 days): inhibition was on average 56 and 64% for DMPP1 and DMPP2, respectively. DMPP did not affect the N mineralization of the crop residues. Under favourable conditions, DCD is able to inhibit the nitrification from crop residues for 50 days and DMPP for at least 95 days. Hence, especially DMPP shows a potential to reduce \({\text{NO}}^{ - }_{3} \) leaching after incorporation of crop residues.