Substitution Of Mineral Fertilizers Research Articles

Assessment of Beef Manure Economic Value by the Method of Equivalent Green and Mineral Fertilizer Substitution

The imperative of sustainable agricultural development, coupled with growing challenges related to climate change reaffirms the importance of manure and increases the demand for it. Due to the underdeveloped market for manure, there is a problem in assessing its economic value, requiring appropriate research on this topic. Thus, this research aimed to assess the manure’s economic value using the method of equivalent substitution. For this purpose, the chemical composition of manure was determined by standard agrochemical analyses concerning the content of the most important mineral elements—nitrogen (N), phosphorus (P2O5), and potassium (K2O). These elements ranged from 0.49–0.60%, 0.15–1.10%, and 0.70–1.07%, respectively, and the content of organic matter ranging from 20.88 to 27.00%. Subsequently, the cost of equivalent substitution was calculated taking into account market prices for commercial fertilizers and organic matter based on the cost of an adequate quantity of white mustard—Sinapis alba L. fresh mass. The average cost of equivalent substitution for manure was determined to be 28.60 USD/t. The results of the applied t-test indicate that there is no statistically significant difference between the market prices of beef manure and the calculated prices of its substitution (t = −1.4069; df = 12; p = 0.1848), which implies that white mustard green manure could replace the deficit in animal-derived manure. Since both animal and green manures unambiguously should be prioritized over chemical fertilizers, future studies will reveal which other crops are applicable for further increments of green manure to make up for insufficient availability of animal manure.

Efficiency of the compensatory scheme of using Organic Acid Nano-Complex microfertilizers in spring wheat cultivation technology

In recent years, significant advances in nanotechnology have increased the ability to produce nanoparticles of physiologically important metals on a large scale, which are now used to improve fertilizer formulations to increase uptake by plant cells and minimize nutrient losses. Fertilizers with nanostructure can increase the efficiency of nutrient use through mechanisms such as targeted delivery, slow or controlled release. The aim of the research is to substantiate a compensatory scheme for the use of biodynamic nanofertilizers (nanocomplex micronutrient fertilizers with organic acids) by partially replacing the main macrofertilizers in the spring wheat fertilization system. The research was conducted on the basis of the educational and scientific laboratory Department of Plant Industry of the National University of Life and Environmental Sciences of Ukraine. In research, there were used the methods of field experiments of A.O. Rozhkov, notching method and scanning method for determination of leaf surface area. The studies showed that it is possible to replace within 30-40% of the recommended amount of mineral fertilizers with biodynamic nanofertilizers in the spring wheat fertilization system. In general, the use of nanofertilizers increased wheat growth and improved yield and yield components. Substitution of mineral fertilizers, Innoparmis Agroscience Biodynamic fertilizers, provides a more favourable 86-88% survival rate of spring wheat plants during the growing season. By replacing 34% of the recommended rate of mineral fertilizers, the content of photosynthetic pigments in wheat leaves increases by 5% and the leaf surface area increases by 7%. The created compensatory schemes for the use of biodynamic nanofertilizers by partial (34% in the wheat fertilization system) replacement of the main macronutrients can increase the yield of spring wheat by 9.9%. The proven possibility of replacing mineral fertilizers with biodynamic nanofertilizers in the fertilization system of agricultural crops will reduce environmental pollution and the economic dependency of using mineral fertilizers against the background of their rapid increase in price in recent years

Changes in P forms and fractions due to the addition of stover and biochar to growing crops in soils amended with stover and its biochar

IntroductionTo comprehend soil P transformation and crop P uptake, it is necessary to understand how the long-term substitution of mineral fertilizers with stover or biochar affects soil properties and P forms. However, the effects of large-scale continuous stover or biochar application on soil P forms and fractions and the response of P uptake by corn are largely unknown. The purpose of this study was to investigate the role of stover and its biochar in the variation of P forms and Hedley-P fractions. MethodsA five-year field experiment in brown soil was carried out using the following treatments: non-fertilizer (CK), chemical fertilizer (NPK), chemical fertilizer + corn stover (SNPK), and chemical fertilizer + biochar (CNPK). Hedley fractionation and 31P nuclear magnetic resonance spectroscopy were used to determine P compounds. Results and discussionThe greatest increases in P uptake occurred during the CNPK treatment, specifically orthophosphate and Resin-P, and coincided with increases in total inorganic P and Hedley-P fractions. On the other hand, total organic P accumulation was found to be highest in the SNPK treatment, as was total inositol hexakisphosphate and orthophosphate diester accumulation. Treatments with SNPK and CNPK significantly increased adenosine monophosphate and DNA. However, no difference was found between NaHCO3-Pi and NaOH-Pi of the NPK, SNPK, and CNPK treatments. Decreasing chemical fertilizer and partially replacing it with biochar in brown soil may increase crop P uptake by degrading applied organic P forms and multiplying inorganic P forms.

Effects of Different Fertilization Methods on Double-Rice Yield and Bacterial Community in Paddy Soil

Fertilizer regimes have profound effects on crop yield, soil fertility, and microbial community structure. However, the impacts of partially substituting mineral nitrogen (N) with organic N and/or controlled-release mineral N and combining with micronutrient fertilizers on soil properties and microbial communities are still unclear in double-rice systems. The objective of this study was to compare rice yield, soil nutrient condition, and bacterial alpha and beta diversity in paddy soil that had been subjected to four fertilizer treatments from 2012 to 2016. The treatments were FP: farmers’ practice with 100% urea N; T1: 64% urea N + 16% manure N; T2: T1 + micronutrient fertilizers; and T3: 40% urea N + 24% controlled-release N + 16% manure N + micronutrient fertilizers. The results showed that there were no considerable differences between rice yields under fertilizer treatments, meaning that reducing farmers’ practice N by 20% did not decrease rice yield. Soil organic matter, total N, pH, and microbial biomass receiving manure did not increase significantly compared with FP. Bacterial beta diversities did not alter under the four treatments. Only two (Verrucomicrobia and Aminicenantes) out of eleven dominant phyla considerably varied under manure treatments. These results indicate that 20% reduction and partial substitution of mineral fertilizer with manure can maintain double-rice yield in paddy soil with limited effects on soil properties and bacterial community structure.

Agricultural biogas plants as a hub to foster circular economy and bioenergy: An assessment using substance and energy flow analysis

Today's agro-food system is typically based on linear fluxes (e.g., mineral fertilizers importation) when a circular approach should be privileged. The production of biogas as a renewable energy source and digestate as an organic fertilizer is essential for the circular economy in agriculture. This study investigates the current utilization of biomass in agricultural anaerobic digestion plants in Switzerland in terms of mass, nutrients, and energy flows to assess its contribution to the circular economy and climate change mitigation through the substitution of mineral fertilizers and fossil fuels. We quantify the system and its benefits in detail and examine potential future developments using different scenarios. Today, agricultural anaerobic digestion provides 1300 TJ/a of biogas. Our results demonstrate that the system could be largely expanded and provide ten times more biogas by 2050 while saving significant mineral fertilizer amounts (over 10 kt/a of dry mass nutrients yielding 38 kt/a of CO2 equivalent).

Life cycle assessment of digestate post-treatment and utilization

Three digestate utilization scenarios for bio-fertilizer production are evaluated with life cycle assessment. The aim is to determine the environmental performance of the digestate post-treatment with the goal to decrease the loss of nitrogen and phosphorus, support circular nutrient management, and increase the substitution of mineral fertilizers. The functional unit (FU) of the study is the utilization of 1 kg dry matter raw digestate, in three scenario designs. Scenario 1 (S1) describes a system where the raw digestate is directly spread on soil. In scenario 2 (S2) the raw digestate is processed by centrifugation with two recovered phases (liquid and solid digestate), which are spread on agricultural soil. In scenario 3 (S3) a more advanced post-treatment system is modelled, where the raw digestate is phase separated with centrifugation followed by drying of the solid digestate and further processing of the liquid digestate with a membrane filtration and a reverse osmosis unit. The studied scenarios show a global warming potential ranging from −0.14 (S3) to −0.36 (S1) kg CO2 eq per FU. The fossil resource depletion per FU was decreased in scenario 1 (−0.053 kg oil eq) and scenario 2 (−0.049 kg oil eq) but increased in scenario 3 (0.002 kg oil eq). The terrestrial acidification potential ranges from 0.09 (S3) to 0.18 (S1) kg SO2 per FU. The digestate post-treatment is a sustainable solution able to tackle the problem of excess nutrients and their management in agricultural areas. It could replace conventional nitrogen removal processes (aerobic biological treatment) by a valorization chain keeping the nutrients in closed loop.

Manure application accumulates more nitrogen in paddy soils than rice straw but less from fungal necromass

Microbial processes involving in nitrogen (N) assimilation mediate the continuous supply of mineral N for crop growth and the reactive N loss in intensively managed agriculture soils. This study aimed to reveal the microbial assimilation role in N accumulation in paddy soils under partial substitution of mineral fertilizer with organic materials (straw or manure), by quantifying the microbial N derived from living biomass and necromass. Rice rhizosphere and bulk soils were collected at a 31-year field trial including five fertilization treatments: no fertilizer (Control), mineral fertilizer alone (NPK), 20% mineral fertilizer substituted by rice straw (NPKS), and 30% and 60% mineral fertilizer substituted by manure (NPKLM and NPKHM, respectively). Incorporation of organic materials increased the total soil N by 22–76% compared to NPK, with a greater increase under manure- than rice straw-treated soils. Both organic inputs enhanced the amounts of living biomass and necromass N by 1.1–1.5 times via stimulating the activity of N cycling genes (chiA, AOA, narG, nirK, nirS, nosZ, nifH) in bulk soils. Although the pools of living biomass and necromass N in soils with manure amendments were 12–34% and 13–22% higher, than those with rice straw incorporation, their corresponding contributions to total N were 7.2–7.4% and 6.2–15% lower, respectively, suggesting a weaker relative microbial contribution in soil N accrual with manure amendments. Rice rhizosphere processes strengthened the role of microbial participation in soil N accumulation, particularly with organic inputs. The relative contribution of fungal necromass N to total N as well as the ratios of fungi to bacteria in both living biomass and necromass were lower under manure amendments than rice straw incorporation. As a whole, as compared with the incorporation of rice straw, the greater N accumulation in paddy soil with manure amendments is associated with the relatively weaker accumulation of fungal necromass and stronger retention of organic debris without microbial processing.

Changes in degree of phosphorus saturation and risk of P loss upon twelve years of manuring and reduced tillage

Adoption of minimum tillage and application of fertilizer integrated with farmyard manure in the long-term has been envisaged to sustain rice-based cropping systems in the Indo-Gangetic plains of India. However, substitution of mineral fertilizer based on crop N requirement results not only in increase of the total P load but also in the distribution of P fractions and soil properties that influence P adsorption. A twelve year old experiment consisting of two tillage (conventional, CT and minimum, MT tillage) and three fertilization treatments (100% inorganic fertilization, IF, 100 and 50% organic fertilization, OF) was examined to unravel the relationship between tillage and manuring effects on distribution of soil P forms vis-à-vis soil test P and how it relates to degree of P saturation (DPS). Reduced tillage intensity and organic fertilization resulted in increase of all P fractions and soluble P. Olsen-P varied from 3.4 to 59.4 mg kg−1 and was exponentially (NH4F-P/NaOH-P) or linearly (Occ-P/H2SO4-P) related to P fractions by direct or indirect effects. Increase in pH and total organic carbon coupled with increase in P load especially in OF and MT treatments resulted in decrease in the P maximum adsorption capacity (PMAC) and P bonding energy of the soil. Consequently, the degree of phosphorus saturation increased with decrease in PMAC and a change point was noted at 13.62% DPS above which soluble P increased more rapidly. Olsen P, which is used as an index of P availability, increased with reduction of tillage and organic manure addition and was closely associated with all the P fractions and DPS. The Olsen P at the change point DPS was 50.4 mg kg−1 which indicated risk of P losses and hence could be used as an index for risk assessment and identify soils that need to be managed agronomically and environmentally to avoid P losses to the environment.

Effect of digestate from anaerobic digestion on Sorghum bicolor L. production and circular economy

The aim of the research was determination the efficiency of application 50 t ha-1 digestate from the process of anaerobic digestion on the productivity of sorghum (Sorghum bicolor L.) on moderately degraded (calcic gleysol) and fertile (chernozem) agricultural land, in southern Banat, Republic of Serbia. In the field experiment during three years digestate amendment led to an increase in the number of leaves by 28.56% and plant height by 5.34%, which led to an increase in yield by 3.40%. The maximum yield was 2018 (41.74 DM t ha-1) on chernozem. The yield of sorghum was lower on calcic gleysol compared to chernozem by 5.43% and was in positive, medium and very significant dependence on precipitation (0.61) and in positive significant correlation with digestate (0.53) and plant height (0.59). Biogas yield reach 157.05 Nm3 t-1 (9582 Nm3 ha-1) on chernozem with digestate. Digestate had a statistically significant positive effect on all tested characteristics of sorghum as well as biogas yield during all three experimental years. The use of digestate as a by-product in the process of producing biogas based on silage of sorghum, allows the substitution of mineral fertilizers and remediation of damaged soil, which contributes to sustainability from the bio-economic and environmental aspects.

Long-term mineral fertilizer substitution by organic fertilizer and the effect on the abundance and community structure of ammonia-oxidizing archaea and bacteria in paddy soil of south China

Ammonia oxidation in the soil is related to nitrogen (N) availability for plants, nitrate loss, and N fertilizer use efficiency, which is important for studies on the N cycle of paddy field ecosystems. Substitution of partial mineral N fertilizer with organic amendments is commonly considered to optimize fertilization practices and reduce the application of mineral N fertilizer in the paddy fields. However, little is known about the effects of this type of fertilization on the relative contribution of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) to soil nitrification. Therefore, a 34-year field trial including five fertilization regimes (CK, without fertilizer; NPK, mineral NPK fertilizer; NPKM1, 70% inorganic N + 30% organic N + PK; NPKM2, 50% inorganic N + 50% organic N + PK; NPKM3, 30% inorganic N + 70% organic N + PK; P: phosphorus, K: potassium) was conducted. AOA and AOB abundance and community structures were determined by quantitative PCR and high-throughput sequencing analyses. Although the abundance of AOA and AOB increased with the increase in the percentage (30%–70%) of organic N substitution, the abundance ratio of AOA to AOB (133.9–84.7) decreased. Soil potential nitrification rate (PNR) increased dramatically (p < 0.05) after replacing chemical N with organic N, and with the increase in the substitution ratio of organic N in paddy soils. AOA and AOB both correlated significantly (p < 0.05) with PNR, but the contribution of AOB to PNR exceeded that of AOA. Soil carbon (C) to N ratio was the best predictor (43.0%) for AOA abundance, while total N and NH4+-N incorporating models were the best predictors (90.3%) for AOB abundance. Variations in AOA composition correlated strongly with fertilizer-induced changes in soil pH and ammonia concentration, whereas the AOB community was only markedly correlated with pH (p = 0.004). The substitution of 30%–70% of mineral N with organic N could increase the soil pH to 5.54–5.87, and that of ammonia concentration to 8.37–24.1 μM, which was the main reason that AOB contributed more to PNR than AOA. These results indicate that the organic substitution fertilizer regime had much stronger effects on the abundance and composition of AOB than AOA, and the potential contribution of AOB to ammonia oxidation in paddy soils should not be ignored after mineral N partial substitution by organic N.

Greenhouse gas emissions from broiler manure treatment options are lowest in well-managed biogas production

The production of broiler meat has increased significantly in the last decades in Germany and worldwide, and is projected to increase further in the future. As the number of animals raised increases, so too does the amount of manure produced. The identification of manure treatment options that cause low greenhouse gas emissions becomes ever more important. This study compares four treatment options for broiler manure followed by field spreading: storage before distribution, composting, anaerobic digestion in a biogas plant and production of biochar. For these options potential direct and indirect greenhouse gas emissions were assessed for the situation in Germany. Previous analyses have shown that greenhouse gas balances of manure management are often strongly influenced by a small number of processes. Therefore, in this study major processes were represented with several variants and the sensitivity of model results to different management decisions and uncertain parameters was assessed. In doing so, correlations between processes were considered, in which higher emissions earlier on in the process chain reduce emissions later. The results show that biogas production from broiler manure leads to the lowest greenhouse gas emissions in most of the analysed cases, mainly due to the emission savings related to the substitution of mineral fertilizers and the production of electricity. Pyrolysis of the manure and subsequent field spreading as a soil amendment can lead to similarly low emissions due to the long residence time of the biochar, and may even be the better option than poorly managed biogas production. Composting is the treatment option resulting in highest emissions of greenhouse gases, due to high ammonia volatilization, and is likely worse than untreated storage in this respect. These results are relatively insensitive to the length of transport required for field spreading, but high uncertainties are associated with the use of emission factors.

Substitution of Mineral Fertilizer with Organic Fertilizer in Maize Systems: A Meta-Analysis of Reduced Nitrogen and Carbon Emissions

Organic fertilizer is an effective substitute for mineral fertilizer that improves crop yield and is environmentally friendly. However, the effects of substitution often vary due to complicated interactions among the organic fertilizer substitution rate (Rs), total nutrient supply, and type of cropping system used. We performed a meta-analysis of 133 maize studies, conducted worldwide, to assess maize yield and environmental performance with substitution of mineral fertilizer with organic fertilizer. At an equivalent nitrogen (N) rate, substituting mineral fertilizer with organic fertilizer increased maize yield by 4.22%, reduced NH3 volatilization by 64.8%, reduced N leaching and runoff by 26.9%, and increased CO2 emissions by 26.8%; however, it had no significant effect on N2O or CH4 emissions. Moreover, substitution with organic fertilizer increased the soil organic carbon sequestration rate by 925 kg C ha−1 yr−1 and decreased the global warming potential by 116 kg CO2 eq ha−1 compared with mineral fertilizer treatment. The net global warming potential after organic fertilizer substitution was −3507 kg CO2 eq ha−1, indicating a net carbon sink. Furthermore, the effect of organic fertilizer substitution varied with the fertilization rate, Rs, and treatment duration. Maize yield and nitrogen use efficiency tended to increase with increasing N application rate following substitution of mineral fertilizer with organic fertilizer. Full substitution reduced N losses more than partial substitution. Further analysis revealed that the yield-optimal Rs for organic N in maize production was 40–60%. Moreover, maize yield and nitrogen use efficiency were further increased after long-term (≥ 3 years) combined use of organic and mineral fertilizers. These findings suggest that rational use of organic and mineral fertilizers improves maize productivity, increases soil organic carbon sequestration, and reduces N and C losses.

Substitution of mineral fertilizer in transplanted rice through nutrient and weed management with herbicide-comlizer mixture

Substitution of mineral fertilizer in transplanted rice through nutrient and weed management with herbicide-comlizer mixture

Yield and biometry of fertilized sugar cane with organomineral fertilizer of sewage sludge and biostimulant

The dependence of mineral fertilizers, increasingly, has brought concern facing the increased demand and because it is a non-renewable mineral resource. The organic fertilization, exclusively, it is impractical in large scale, however, the combination of organic and mineral sources have already proved to be feasible, both from the point of view of nutrition of plants as well as in the aspect of recycling of urban and industrial waste by agriculture. This research had as objective to determine the efficiency of aorganomineral fertilizer formulated on the basis of sewage sludge in substitution of mineral fertilizer in the cultivation of sugar cane in environments with different levels of soil fertility. An experiment was conducted in greater soil fertility, in the Institute Federal Goiano– Campus, Morrinhos-GO, Brazil. The other, less soil fertility, was implanted in the ethanol industry Tijuco Valley, located in Rio do Peixe, district of Prata-MG, Brazil. The experimental design was randomized blocks in a factorial 5 x 2 +1 being five doses, with and without a biostimulant plus an additional with mineral fertilization, in four replications. The doses were in function of fertilization recommendation of planting and coverage for each environment, consisting of: 100 % of the mineral source and percentage 0; 60; 80; 100 and 120 % of organomineral fertilizer. We evaluated the productivity, tillering, diameter and height of stem in Prata-MG the different percentages of the fertilization of planting favored and increased productivity, height and stem diameter of sugar cane; the use of biostimulants not contributed to increase crop yield. In Morrinhos-GO, the different percentage of planting fertilization did not increase the productivity, tillering, height and diameter of the sugarcane stem; the use of biostimulants increases the productivity yield of sugarcane. Organomineral fertilizer based on biosolids is similar to fertilization with mineral fertilizer in environments.

Greenhouse Gas Emissions as Affected by Fertilization Type (Pig Slurry vs. Mineral) and Soil Management in Mediterranean Rice Systems

The great increase in livestock production in some European areas makes it necessary to recycle organic slurries and manures and to integrate them in crop production. In Northeast Spain, the application of pig slurry (PS) is being extended to alternative crops such as rice due to the great increase in pig production. However, there is a lack of information of the effect of substitution of synthetic fertilizers with pig slurry on greenhouse gas (GHG) emissions in rice crop, and this information is key for the sustainability of these agricultural systems. The aim of this study was to evaluate the effect of the substitution of mineral fertilizers by PS on GHG emissions in Mediterranean flooded rice cultivation conditions under optimal nitrogen (N) fertilization. Two field experiments were carried out in two different (contrasting) soil types with different land management. Site 1 had been cultivated for rice in the previous three years with no puddling practices. Site 2 had been cultivated for rice for more than 15 years with puddling tillage practices and had higher organic matter content than site 1. The cumulative nitrous oxide emissions during the crop season were negative at both sites, corroborating that under flooded conditions, methane is the main contributor to global warming potential rather than nitrous oxide. The substitution of mineral fertilizer with PS before seeding at the same N rate did not increase emissions in both sites. However, at site 1 (soil with lower organic matter content), the higher PS rate applied before seeding (170 kg N ha−1) increased methane emissions compared to the treatments with lower PS rate and mineral fertilizer before seeding (120 kg N ha−1) and complemented with topdressing mineral N. Thus, a sustainable strategy for inclusion of PS in rice fertilization is the application of moderate PS rates before seeding (≈120 kg N ha−1) complemented with mineral N topdressing.

Partial substitution of mineral fertilizer with biofertilizer enhances cauliflower nutritional quality, yield, and soil characteristics

AbstractCauliflower (Brassica oleracea L. var. botrytis L.) is as an important ingredient in many healthy diets worldwide, but there is a lack of scientific knowledge about fertilizer management during cauliflower production. We conducted field experiments in Yuzhong, China, in 2015 and 2016 to determine the effects of the integrated use of biofertilizer and a reduced rate of mineral fertilizers on cauliflower growth, quality, and yield and on soil characteristics. Three different rates of mineral fertilizer (60, 80, and 100% of the mineral fertilizers; 100% rate = 400 N kg ha−1, 225 kg P2O5 ha−1, 125 kg K2O ha−1) and 500 kg ha−1 biofertilizer were applied to the crop with three replicates. The results showed that the use of the mineral fertilizer at 80% in combination with biofertilizer (80% BF) increased the vitamin C content of cauliflower heads by 39.5% in 2015 and 43.6% in 2016 compared with the 100% mineral fertilization treatment (100% MF). The 80% BF treatment decreased the nitrate content by 27.1% in 2015 and 27.6% in 2016 and improved the soluble sugar contents by 19.1% in 2015 and 29.5% in 2016 compared with the 100% MF treatment. However, the effect of the 80% BF treatment on marketable yield was found to be nonsignificant. Biofertilization also improved the soil organic matter, available N, P, and K, and enzyme activities. We observed that conjugative use of biofertilizer and a reduction in mineral N–P–K fertilizer can be used successfully in cauliflower production without compromising marketable yields.

Characteristics of soil nitrogen cycle and mechanisms underlying the increase in rice yield with partial substitution of mineral fertilizers with organic manure in a paddy ecosystem: A review

Partial substitution of mineral fertilizers with organic manure is a key strategy for stable and increase crop yield accompanying with zero growth of mineral fertilizers. Based on recent stu-dies, we reviewed the effects of partial substitution of mineral fertilizers with organic manure on rice yield, nitrogen utilization efficiency, soil nitrogen fractions, and microbial nitrogen fixation, ammonification, nitrification, and denitrification in rice paddy ecosystems. We further compared the cha-racteristics of soil nitrogen cycle of mineral fertilizers alone and partial substitution of mineral fertili-zers with organic manure. The partial substitution altered key processes of nitrogen cycling, including enhancement of ammonification, mediation of nitrification and denitrification, reduction of ammonia volatilization and nitrogen loss, improved the status of nitrogen supplements (enriching the supplement of low-molecular-weight organic nitrogen, adjusting the distribution of inorganic nitrogen components, increasing the amount of microbial biomass nitrogen, and decreasing the loss of total nitrogen), improved soil nitrogen supply (increasing supply of small molecule organic nitrogen, coordinating inorganic nitrogen components and proportions, and increasing soil microbial biomass nitrogen and total nitrogen fixation), which promoted nitrogen uptake and regulated nitrogen allocation in rice plant to realize stability and enhancement of rice yield.

Biofertilizante como solução nutritiva para produção de alface hidropônica no Alto Sertão paraibano

O uso de sistemas hidropônicos por agricultores familiares do semiárido paraibano permite uma produção continuada de hortaliças frente às limitações hídricas, típico desta região, contudo, o difícil acesso e o alto custo dos fertilizantes minerais é um fator limitante desta prática. Neste sentido, objetivou-se avaliar o potencial do uso de biofertilizante anaeróbio bovino na substituição dos fertilizantes minerais, no cultivo de alface do grupo crespa cv. Cristina. O trabalho foi conduzido em casa de vegetação, instalada no Instituto Federal da Paraíba, Campus Sousa. Avaliaram-se quatro doses fertilizantes minerais mais biofertilizantes: Bio+0%; Bio+25%; Bio+50%, Bio+75% com quatro repetições, em blocos casualizados. Foram avaliadas as variáveis massas de matérias secas das folhas e total, o número total de folhas, área foliar e produtividade. A redução das doses de fertilizantes minerais comprometeu o crescimento e consequentemente a produção de alface, onde a máxima produção da parte comercial, foi de 43,0 g planta ̵¹, sendo obtida com o tratamento de 75% da combinação das doses de fertilizantes minerais mais biofertilizante.

Reduced mineral fertilization coupled with straw return in field mesocosm vegetable cultivation helps to coordinate greenhouse gas emissions and vegetable production

The partial substitution of mineral fertilizers with straw in agricultural soils could help to control soil acidification, reduce the risk of eutrophication from agricultural runoff, and increase the utilization efficiency of straw. However, the effects of such coupled practices on greenhouse gas (GHG) emissions and production yields in vegetable fields are not clear. Therefore, the objectives of this study were to (1) understand methane (CH4) and nitrous oxide (N2O) emissions in response to the same amounts of straw return with varied amounts of mineral fertilizers, and (2) to identify a solution which could better coordinate GHG emissions, vegetable production yield, and the utilization of agricultural straw following disposal. We conducted four-season (lettuce-cabbage-chili-lettuce) vegetable cultivation for 1 year using a control treatment (CT), mineral fertilization only (F), and four mineral fertilization treatments plus maize straw (FS, 0.7FS, 0.6FS, and 0.5FS). We then examined seasonal changes of CH4 and N2O fluxes, CH4 and N2O cumulative emissions, soil organic carbon (SOC), nitrate nitrogen (NO3−-N) and ammonium nitrogen (NH4+-N) content, vegetable yields, global warming potential (GWP), greenhouse gas intensity (GHGI), and N2O emission factors (EF). Compared to the F treatment, the application of maize straw increased the N2O flux significantly in the FS, 0.7FS, 0.6FS, and 0.5FS treatments. In treatments with added straw, the reduced application of mineral fertilizer led to a reduction in the cumulative N2O emission; this was due to the reduced content of NO3−-N content. The lowest CH4 flux and cumulative CH4 emission were observed in the 0.7FS treatment; this may be due to a form of competitive oxidation between CH4 and NH4+-N from urea. Furthermore, the application of maize straw in combination with a full dose of mineral fertilizers led to high GWP and GHGI values, which showed increases of 88.7% and 78.8%, respectively, in comparison with the F treatment. When taking SOC storage variations into account, which were caused by straw decomposition during cultivation, we identified a negative net GHGI (NGHGI) value (− 0.0448 kg CO2-eq kg−1 yield) in the 0.7FS treatment. This indicated that the NGHGI had decreased by 116.2% relative to the F treatment when based on similar vegetable yields. Straw combined with 70% mineral fertilizer led to better GHG emissions and vegetable yield when taking into account the carbon sequestration and decomposition caused by the addition of straw.

Biogas digestates are not an effective nutrient solution for hydroponic tomato (Lycopersicon esculentum L.) production under a deep water culture system

The generation of energy through anaerobic digestion using animal manures is being promoted as an environmentally sustainable method of managing animal wastes. However, sustainability of biogas production is reliant on the sustainable utilization of the digestates that emanate from the process. Our study evaluated the effects of the biogas digestates on crop phytotoxicity and their fertilizer potential as a nutrient solution in hydroponic tomato production. Biogas digestates diluted up to 40% (v/v) resulted in significantly (P < 0.05) the lowest relative seed germination (RSG) in all vegetables evaluated in our study. The highest RSG was observed in the 10% biogas digestates, which was higher than the control treatment. For the crop growth study, relative to the control,the treatments with 20%, 40% and 60% mineral fertilizer substitution resulted in 39.4%; 22.8% and 8.7% significantly (P < 0.05) lower chlorophyll content, respectively. On average, the treatments with biogas slurry, though substituted with mineral fertilizers, resulted in a 275% lower fresh fruit yield compared to the control treatment. However, with biogas digestates, the sugar content in the tomato fruits significantly increased, whilst the heavy metal content was below that recommended limit when irrigation water is used. The results of our study demonstrated that cow based digestates are not a suitable nutrient media for hydroponic tomato production. Moreover, even with mineral fertilizer supplementation, only the control treatment containing only mineral hydroponic fertilizer resulted in positive growth and yield in tomatoes.