Fertilizer Amendments Research Articles

Effects of fertility amendments on weed growth and weed–crop competition: a review

AbstractMacronutrient inputs to annual cropping systems can benefit weeds as well as crops, sometimes decreasing or eliminating the benefits of fertilization. This interaction between fertility management and integrated weed management is becoming increasingly important as these fields increase their focus on efficiency and prevention, respectively. The risk of increased weed competition reflects the fact that weed biomass and height may be highly responsive to nitrogen, phosphorus, and/or potassium. This generalization is supported by monoculture studies of species such as redroot pigweed (Amaranthus retroflexusL.), common lambsquarters (Chenopodium albumL.), and barnyardgrass [Echinochloa crus-galli(L.) P. Beauv.] and by ecological theory. However, field studies indicate variation in the effects of macronutrients on weed–crop competition and crop yield, even within species groups. To address challenges in interpreting, comparing, and extrapolating from these diverse reports, we propose a conceptual framework that summarizes the mechanisms underlying observed variation within and between studies. This framework highlights functional traits and trends that help predict yield outcomes in binary weed–crop interactions. Important factors include timing of emergence, maximum heights of the weed and crop, and relative responsiveness to the added nutrient. We also survey recent work on the effects of nutrient source (e.g., the composition of organic amendments) on weed–crop competition. Because different sources vary in their nutrient release dynamics and supplied nutrient ratios, they may have dramatically different effects on weed–crop competition and crop yield. Finally, we offer a guide to best practices for studies of fertility effects on weed–crop competition. Although this review highlights several topics requiring further research, including fertility effects on multispecies interactions and interactions with other environmental factors, emerging methods offer considerable promise. Ultimately, an improved understanding of nutrient effects on weed–crop competition will contribute to the efficient and effective management of diverse cropping systems.

Potential for Mycorrhizae-Assisted Phytoremediation of Phosphorus for Improved Water Quality.

During this 6th Great Extinction, freshwater quality is imperiled by upland terrestrial practices. Phosphorus, a macronutrient critical for life, can be a concerning contaminant when excessively present in waterways due to its stimulation of algal and cyanobacterial blooms, with consequences for ecosystem functioning, water use, and human and animal health. Landscape patterns from residential, industrial and agricultural practices release phosphorus at alarming rates and concentrations threaten watershed communities. In an effort to reconcile the anthropogenic effects of phosphorus pollution, several strategies are available to land managers. These include source reduction, contamination event prevention and interception. A total of 80% of terrestrial plants host mycorrhizae which facilitate increased phosphorus uptake and thus removal from soil and water. This symbiotic relationship between fungi and plants facilitates a several-fold increase in phosphorus uptake. It is surprising how little this relationship has been encouraged to mitigate phosphorus for water quality improvement. This paper explores how facilitating this symbiosis in different landscape and land-use contexts can help reduce the application of fertility amendments, prevent non-point source leaching and erosion, and intercept remineralized phosphorus before it enters surface water ecosystems. This literature survey offers promising insights into how mycorrhizae can aid ecological restoration to reconcile humans’ damage to Earth’s freshwater. We also identify areas where research is needed.

Growth and flowering of young cocoa plants is promoted by organic and nitrate-based fertiliser amendments

SummaryCocoa (Theobroma cacao) farmers in Sulawesi, Indonesia typically use subsidised, ammonium-based rice fertilisers that in combination with poor agricultural practices have resulted in soil acidification, loss of organic matter, aluminium toxicity and lower soil fertility. As a result, these soils are only marginally appropriate for replanting cocoa to boost production. A field experiment was performed to test alternative soil amendments for successful replanting of cocoa on these deficient soils. In a trial with a randomised block design, 6-month old seedlings, top-grafted with the local MCC02 clone, were planted under light Gliricidia sepium shade and after 3 months treated quarterly with two options of mineral fertilisers: either a customised fertiliser, consisting of Nitrabor (a combination of calcium nitrate and boron), dolomite, rock phosphate and KCl or a NPK/urea mix used by farmers, each supplied with or without ‘micronutrient’ rock salt, organic fertiliser and beneficial microorganisms or their culture medium, a mixture of chitin and amino acids (a total of 20 treatments). Over a 4-year period, the marginal mean rates of stem diameter increment and flowering score were higher in customised fertiliser than NPK/urea treatments. The average growth rate was highest in the first year and was increased by supplying organic fertiliser. A significant correlation (r = 0.22, p < 0.05) occurred between growth and available P, but concentrations of available P were higher in the NPK/urea plots, which also had lower mean growth rates. Combined supply of organic fertiliser and microbes increased available P, as well as growth rates, in both the customised and NPK/urea treatments. In contrast, NPK/urea-treated plots without these amendments demonstrated very low growth rates. The customised formulation was more effective with or without added organic fertiliser or inoculated microbes. Micronutrient supply stimulated flowering. Growth rates in trees supplied with NPK/urea were also promoted by micronutrients. Leaf flush production occurred in regular cycles and was unaffected by the nutrient amendments. After 3 years, the customised and organic fertiliser application increased soil pH and exchangeable Ca and Mg concentrations, although they remained below recommended levels for cocoa production. These treatments had little impact on soil C content (about 1.3%) which was also deficient. Exchangeable Al and total Zn concentrations were higher in soils amended with NPK/urea. The results of the trial provide evidence that utilisation of organic fertiliser in combination with customised nitrate-based formulations improves cocoa establishment, growth and soil properties and should be recommended as a replacement for the NPK/urea fertilisers traditionally used by farmers.

Response of Soil Bacterial Community to Application of Organic and Inorganic Phosphate Based Fertilizers under Vicia faba L. Cultivation at Two Different Phenological Stages

It is essential to investigate to which extent and how specifically soil–plant–microbe interactions can be conditioned by different agricultural practices. Legumes such as Vicia faba is one of the essential functional group in intercropping and crop rotations due to its higher N fixing capacity. Hence, it is important to study the living microbial community of this legume. Further, it is also expected that fluctuations in soil microbial diversity and composition could be complemented by plant phenological stages and different fertilizer amendments. Thus, we investigated bacterial community composition in soil treated with phosphate-based inorganic and organic fertilizers, in the presence of Vicia faba plants at flowering and fruiting time using NGS 16S rRNA gene amplicon sequencing. Further, the evaluation of plant biomass parameters under different fertilizer treatments was also carried out. The presence of the Vicia faba plant increased the abundance of N fixing bacterial such as Bardyrhizobium, Microvirga (Rhizobiales), Arthrobacter, and Psuedoarthrobacter (Actinomycetales) in soil. Fluctuation in composition and diversity of bacterial community was further supplemented by plant phenological stages. These alterations could be due to changes that occurred in the plant nutrient requirement and varied root exudation patterns at a specific phenological stage. Further, fertilizer treatments also have a profound effect on the diversity and structure of the bacterial community. Organic fertilizers, especially vegetable tanned leather waste (VTLW), have a stronger effect on the composition and diversity of bacterial community compared to inorganic fertilizer (PT—triple superphosphate). Alpha-diversity was significantly decreased by both organic and inorganic amendments, especially a species evenness because each fertilizer tends to stimulate the growth of distinctive microbes that dominated the community of amended soil. Proteobacteria, Actinobacteria, and Cyanobacteria were the most abundant phyla, and Chelatococcus, Cyanobacteria, Sphingomonas, and Microvirga were a most abundant genus that contributed most in co-occurrence pattern, which suggests that these generalists are adapted to a variety of environments. These indicate that plant presence was a key, dominating factor, followed by fertilizers and time, in affecting soil bacterial diversity and composition. Plant recruits system (fertilization and time) -specific taxa due to differences in available nutrients and energy sources among different treatments during different growth stages. Further, fertilizer treatments did not have a stronger effect on plant production as compared to the effect on microbial community, which highlights that organic fertilizers did not tend to increase plant production. Thus, organic and inorganic amendments with matched macronutrients could have a similar impact on crop yields.

Active phoD-harboring bacteria are enriched by long-term organic fertilization

PhoD-harboring microorganisms are crucial for the regulation of soil phosphorus (P) cycling through the secretion of alkaline phosphomonoesterases and are also known to be sensitive to fertilizer inputs. However, the impacts of long-term mineral and organic fertilizer inputs on active phoD-harboring functional communities in soils remain largely unknown. In the present study, 18O-DNA-stable isotope probing coupled with high-throughput sequencing was utilized in order to characterize active phoD-harboring functional bacterial communities in soils subjected to long-term no-fertilizer (Control), mineral-only fertilizer (NPK), organic-only fertilizer (M), and the combination of mineral and organic fertilizer (NPKM) amendments. Total and active phoD gene abundance decreased in soils amended with long-term mineral fertilizer, but increased in soils under organic fertilizer amendment, compared with the non-fertilized soils. A total of 51 active phoD-harboring bacterial OTUs, mainly belonging to Actinobacteria, were identified in this study. Organically amended soils harbored a higher diversity of active bacterial community. In the active phoD-harboring functional community, Rhodococcus comprised approximately 99% of the total relative abundance in the unfertilized soil, whereas Nocardiopsis and Bacillus accounted for approximately 62% and 24%, respectively, in mineral-only fertilized soils. Active phoD-harboring communities were dominated by members of the genera Streptomyces (26–60%), Nocardia (5–9%) and Gordonia (23–41%) in all organically fertilized soils, including M and NPKM. Overall, these long-term fertilization regimes altered the abundance, richness and composition of the active phoD-harboring functional microbial community. This study provides novel insights into the responses of the active functional bacterial community that is responsible for soil P mineralization to differing long-term fertilization regimes.

Effects of Nitrogen Fertilization on Mycorrhizal Infection, Nodulation and Growth of Phaseolus vulgaris L.

Summary The common bean (Phaseolus vulgaris L.) has been the subject of a number of studies and has been described by many authors as a legume with low nitrogen fixing potential compared to other legume species. The first objective of this study is to assess the development and growth of P. vulgaris L. var. Djedida and its yield at different developmental stages (vegetative, flowering and fruiting), in the presence and absence of nitrogen fertilizer (Urea 46) in an arid climate and in a soil containing high level of CaCO3 and assimilable phosphorus. The second objective is to carry out a survey on nodulation, number of spores and mycorrhizal infection under these conditions. The results showed that the nitrogen fertilizer amendment is mainly significant (p< 0.0001) for various morphological parameters. Indeed, great improvement was observed on the majority of the morphological parameters with considerable percentages. However, no significant effect was reported for the roots length. In addition, a negligible number of nodules were obtained in the plot without fertilization and no significant effect on the number of spores was recorded. Furthermore, the effect of fertilization on the arbuscular intensity (a%, A%) and on mycorrhizal colonization (M%, m%) of the roots was found to be significant. The soil in the arid region of Biskra showed significant mycorrhizogenic potential, although the conditions in this region were not very favorable for their development, which could constitute an effective biological resource to improve the tolerance of host plants to biotic and abiotic constraints.

Influence of agricultural amendments on arsenic biogeochemistry and phytotoxicity in a soil polluted by the destruction of arsenic-containing shells

Agricultural soils can contain high arsenic (As) concentrations due to specific geological contexts or pollution. Fertilizer amendments could influence As speciation and mobility thus increasing its transfer to crops and its toxicity. In the present study, field-relevant amounts of fertilizers were applied to soils from a cultivated field that was a former ammunition-burning site. Potassium phosphate (KP), ammonium sulfate and organic matter (OM) were applied to these soils in laboratory experiments to assess their impact on As leaching, bioavailability to Lactuca sativa and microbial parameters. None of the fertilizers markedly influenced As speciation and mobility, although trends showed an increase of mobility with KP and a decrease of mobility with ammonium sulfate. Moreover, KP induced a small increase of As in Lactuca sativa, and the polluted soil amended with ammonium sulfate was significantly less phytotoxic than the un-amended soil. Most probable numbers of AsIII-oxidizing microbes and AsIII-oxidizing activity were strongly linked to As levels in water and soils. Ammonium sulfate negatively affected AsIII-oxidizing activity in the un-polluted soil. Whereas no significant effect on As speciation in water could be detected, amendments may have an impact in the long term.

Application of bio-organic fertilizer, not biochar, in degraded red soil improves soil nutrients and plant growth

Biochar (B) and fertilizer (organic fertilizer, OF and synthetic fertilizer, CF) are frequently applied to improve ecosystem function and increase crop productivity in degraded soil. Nonetheless, the effects and mechanism of biochar in combination with OF and CF on degraded red soil was unclear. The aim was to study the influence of biochar and fertilizer related amendments in a degraded red soil on the rhizosphere microbiome of Plantago lanceolate under controlled condition. Soil was amended with rice husk biochar (5%, w/w), bio-organic fertilizer (5%, w/w), biochar (5%, w/w) + bio-organic fertilizer (5%, w/w), synthetic fertilizer (0.5%, w/w) and biochar (5%, w/w) + synthetic fertilizer (0.5%, w/w), in a greenhouse experiment. Illumina high throughput sequencing and PICRUSt analysis of functional gene prediction were employed to characterize the rhizosphere microbial community and its functional component involved in nitrogen (N) cycling and soil carbon (C) degradation. At harvest of 90 days, plant growth was highest with bio-organic fertilizer amendment, followed by biochar + synthetic fertilizer. Compared to the control, bio-organic fertilizer related amendment increased microbial diversity indexes (Ace, Sobs and Chao), but synthetic fertilizer decreased them significantly. Principal co-ordinates analysis showed that the microbial community was separated by the type of fertilizer, but not biochar. Redundancy analysis (RDA) at the phylum level further showed that electrical conductivity and soil carbon affected bacterial community, whereas alkaline nitrogen had a significant effect on the fungal community. PICRUSt analysis exhibited that bio-organic fertilizer related amendments decreased the abundance of labile C (glucoamylase and beta-galactosidase) and increased recalcitrant C degrading genes (catalase and endoglucanase). Predicted N cycling genes abundance increased with the addition of bio-organic fertilizer (nifD, amoA·amoB, Hao, nrfA, nirK and nosZ) and biochar + bio-organic fertilizer (amoA·amoB, Hao, narG, nrfA, nirk and nosZ). Biochar did not alter the relative abundance of phylum-level taxa and predicted functional genes in the absence of fertilizer. Via regulation of soil microbial community, bio-organic fertilizer amendment had positive impacts on N cycling, however, enhanced recalcitrant C degrading and inhibited labile C degrading.

Role of Variety and Fertilizer Practices on Cowpeas (Vigna unguiculata) Yield and Field Incidence of the Parasitic Weed Alectra vogelii (Benth) in Central Malawi

Grain legumes are an important component of the food systems in Malawi. The parasitic legume witchweed species Alectra vogelii (Benth) is among the problem pests with serious infestations in groundnuts (Arachis hypogea), soybeans (Glycine max), cowpeas (Vigna unguiculata) and other legumes. A study was conducted in 2013/14 and ‘14/15 seasons to evaluate the effects of three cowpea varieties (IT82E-16, Sudan 1 and Alectra-resistant Mkanakaufi) and fertilizer practices (no fertilizer applied, 5 t ha-1 cattle manure and 100 kg ha-1 of inorganic 23:21:0+4S on cowpea grain yield, yield components and Alectra emergence at three sites in central Malawi. Cowpea grain yields ranged 400-2400 kg ha-1. There were significant (P < 0.05) variety effects on yield in 4 of 6 site-years, with variety IT82-16 consistently giving the highest yields (range 1200-2400 kg ha-1). There were significant variety effects on A. vogelii emergence with Mkanakaufiti having no Alectra throughout. Application of cattle manure strongly suppressed A. vogelii in 6 site-years all at 60 days after planting, while inorganic fertilizer suppressed Alectra in 3 of the 6 site-years. Cattle significantly but marginally (about 250 kg ha-1) increased yield in 2 of the 6 site-years. The results show potential to suppress A. vogelii with cattle manure application. However, further studies are required to understand the causes of the limited yield response under manure or fertilizer application to make the practices attractive to farmers. More variety improvement studies to produce a range of varieties with better local adaptability and response to fertility amendments are recommended.

Common bean (Phaseolus vulgaris L.) root rot in humid lowland: Occurrence, and assessment of biotic and agronomic factors for mitigation prospects

Biotic and abiotic constraints jeopardize the expansion of common bean (Phaseolus vulgaris L.) cultivation to the Cameroon warmer lowlands. The crop is traditionally perceived as a cooler region crop unsuited for the humid tropical areas. We surveyed 78 farmer's fields during the 2015 and 2016 growing seasons, across 7 sub-divisions in the lowland agro-ecological zone of the Centre Region of Cameroon, to document the occurrence of the common bean root rot (BRR) epidemic, the identification of causal pathogens, as well as related agro-ecological variables. We found that BRR occurred in all the surveyed farmer's fields, with disease incidence ranging from 7.4% to 92.4% and disease severity from 3.7 to 9 (On the 1–9 disease rating scale). The disease distribution was closely related to tillage, cropping systems, plant age and variety and physiological status in both seasons. The simple linear regression model and the Pearson correlation revealed significantly negative correlations between the soil pH and phosphorus content, and the disease incidence and severity. Five causative fungal genera were identifies, with varying occurrence: Fusarium spp. (65.4%), Pythium spp. (4.2%), Sclerotium spp. (5.1%), and Macrophomina spp. (8.2%), with Fusarium being the most represented and widespread pathogen irrespective of sampling field and season. Fusarium occurred singly, or in complex with the other pathogenic fungal genera. This study provides clear evidence of high prevalence of BRR disease in the humid lowlands of Cameroon, and suggests deep ploughing and phosphoric fertilizer amendment with basic soil for managing BRR in lowland agro-ecosystems.

A new strategy for evaluating the improvement effectiveness of degraded soil based on the synergy and diversity of microbial ecological function

Sandy soil, as an important transition phase to desertification, has been an important environmental issue of global concern. This study explored the combined effects of organic fertilizer amendment and arbuscular mycorrhizal fungus (AMF)-assisted phytoremediation on sandy soil improvement and revealed the mechanism of soil improvement from the perspective of microbial interactions. Furthermore, soil quality and soil improvement effectiveness were evaluated from the perspective of microbial ecological function. A greenhouse pot experiment with four treatments, including control (CK), single AMF-assisted amendment (RI), single organic fertilizer amendment (OF) and combined amendment (OF + RI) was set up. The results showed that the biomass and nutrient element contents of Nitraria sibirica, soil enzyme activities, soil organic carbon and soil water-stable macroaggregates (>0.25 mm) were highest in the OF + RI treatment. Using Illumina high-throughput sequencing, we found that the combined amendment had a significant impact on soil microbial diversity, community composition and ecological function. Chloroflexi, Basidiomycota, Blastocladiomycota and Sordariomycetes were significantly dominant microorganisms in the OF + RI treatment. Network analysis revealed significantly positive or negative linear relationships between bacteria/fungal groups and soil nutrient elements. In conclusion, the synergy and diversity of microbial ecology function can be used as a key indicator to assess the improvement effectiveness of various soil. Under the combined effects of reasonable nutrient supplementation and effective cooperation of the microbial community, the physicochemical amendment and microbe-assisted phytoremediation will more positively drive sandy soil improvement. This study proposes new insights for effectively evaluating the soil improvement effectiveness and improving sandy soil or managing desertification.

Co-application of poultry-litter biochar with Azolla has synergistic effects on CH4 and N2O emissions from rice paddy soils

Poultry-litter biochar and Azolla as green manure amendments are reported to enhance paddy soil fertility and rice yields. However, whether their co-application in lowland rice paddies has synergistic effects and whether those benefits are accompanied by greenhouse gas (GHG) emissions remains unknown. The objective of this study was to determine the effects of poultry-litter biochar (hereafter: biochar) and its co-application with Azolla as green manure (hereafter: Azolla), on the simultaneous methane (CH4) and nitrous oxide (N2O) emissions from a lowland paddy soil planted with rice during a single rice growing season in Tsuruoka, Yamagata, Japan. Biochar and Azolla amendments were applied once before rice was transplanted at a density of 20 t ha−1 and 133.9 kg N ha−1, respectively. Compared with NPK, NPK + biochar, and Azolla only treatments, Azolla and biochar co-application (i.e., Azolla + biochar) significantly increased CH4 emissions by 33%–197.6% in the early stages of rice growth (before 63 days after transplanting, DAT), but did not significantly influence CH4 emissions at both late rice growth stages (after 63 DAT,) and whole rice growth period (112 DAT). Conversely, Azolla + biochar significantly reduced N2O emissions by 83.0%–97.1% before 63 DAT, and by 76.4%–95.9% during the whole rice growth period at 112 DAT, with a significantly high interaction between biochar and fertilizer amendments. There were no significant N2O emission differences among all treatments after 63 DAT. Additionally, Azolla + biochar significantly increased rice grain yield by 27.3%–75.0%, and consequently, decreased both yield-equivalent CH4 emissions by 24.7%–25.0% and N2O emissions by 81.8%–97.7%. Our findings suggest that the co-application of poultry-litter biochar and Azolla as green manure offers a novel approach to increase rice yield while reducing the emissions of non-carbon dioxide greenhouse gases.

Influence of planting basins on selected soil quality parameters and sorghum yield along an agro-ecological gradient in South Eastern Zimbabwe

Planting basins are an important soil and water conservation technology. This study evaluated the effects of basins on soil organic carbon (SOC) stocks, aggregate stability (Ima), bulk density, soil moisture retention and sorghum yield in agro-ecological regions III, IV and V of Chipinge district. The experiment consisted of three treatments; namely planting basins (basins) with goat manure and inorganic fertilizer application, hand hoeing with similar fertility amendments (FP+) and hand hoeing without fertility amendments (FP). It was hypothesized that planting basins with fertility amendments would improve the selected soil quality parameters and sorghum yield. Only planting basins significantly (p˂0.05) improved soil quality parameters in the 0-15 cm depth and bulk density, Ima, SOC stocks ranged from 1356 to 1451 kg/m3; 314 to 450 and 14.18 to 25.55 Mg ha-1 respectively. Planting basins significantly increased (p<0.05) sorghum yield relative to hand-hoeing practices (FP+ and FP) with average grain yield of 2.68, 1.72 and 1.32 t ha-1 in agro-ecological regions III, IV and V, respectively. When compared to FP+ and FP, basins increased grain yield by >130% in all the 3 agro-ecological regions. The hypothesis was accepted and it was concluded that basins improve soil properties and sorghum grain yield in agro-ecological regions III, IV and V. Considering the soil and crop productivity benefits highlighted in this study, there is a strong justification for the widespread promotion and adoption of planting basins in semi-arid agro-ecological regions of Zimbabwe.

Evaluating recycling fertilizers for tomato cultivation in hydroponics, and their impact on greenhouse gas emissions

Soilless culture systems offer an environmentally friendly and resource-efficient alternative to traditional cultivation systems fitting within the scheme of a circular economy. The objective of this research was to examine the sustainable integration of recycling fertilizers in hydroponic cultivation—creating a nutrient cycling concept for horticultural cultivation. Using the nutrient film technique (NFT), three recycling-based fertilizer variants were tested against standard synthetic mineral fertilization as the control, with 11 tomato plants (Solanum lycopersicum L. cv. Pannovy) per replicate (n = 4) and treatment: two nitrified urine-based fertilizers differing in ammonium/nitrate ratio (NH4+:NO3−), namely (1) “Aurin” (AUR) and (2) “Crop” (CRO); as well as (3) an organo-mineral mixture of struvite and vinasse (S+V); and (4) a control (NPK). The closed chamber method was adapted for gas fluxes (N2O, CH4, and CO2) from the root zone. There was no indication in differences of the total shoot biomass fresh matter and uptake of N, P and K between recycling fertilizers and the control. Marketable fruit yield was comparable between NPK, CRO and S+V, whereas lower yields occurred in AUR. The higher NH4+:NO3− of AUR was associated with an increased susceptibility of blossom-end-rot, likely due to reduced uptake and translocation of Ca. Highest sugar concentration was found in S+V, which may have been influenced by the presence of organic acids in vinasse. N2O emissions were highest in S+V, which corresponded to our hypothesis that N2O emissions positively correlate with organic-C input by the fertilizer amendments. Remaining treatments showed barely detectable GHG emissions. A nitrified urine with a low NH4+:NO3– (e.g., CRO) has a high potential as recycling fertilizer in NFT systems for tomato cultivation, and S+V proved to supply sufficient P and K for adequate growth and yield. Alternative cultivation strategies may complement the composition of AUR.

Long Term Effect of Tillage and Organo-Mineral Fertilizer Application on Phosphorus Dynamics on Ferric Lixisol in Burkina Faso

A Pot experiment was conducted on 30 years long term soils under different soils management to evaluate the effect of organic amendments and soil tillage on phosphorus evolution in Ferric Lixisol. Two (2) levels of incubation with and without sorghum bicolor were used with six (6) treatments: (1) Tillage with animal traction + 10 t manure / ha / year + 100 kg NPK (14-23-14-6S-1B) / ha + 50 kg urea (46 % N); (2) Tillage with animal traction + 100 kg NPK (14-23-14-6S-1B) / ha + 50 kg urea (46 % N); (3) Minimum tillage+ 10 t manure / ha / year + 100 kg NPK (14-23-14-6S-1B)/ ha + 50 kg urea (46% N); (4) Minimum tillage + 100 kg NPK (14-23-14-6S-1B) / ha + 50 kg urea (46 % N); (5) 30-years-old fallow and (6) control plot (continuous sorghum without fertilizer) from soil fertility sustainability trial. Each treatment was pretreated with carbon plus nitrogen or without nitrogen before the experiment. The results showed that tillage increased P availability by 70 to 273 % compared to fallow in general and the use of organic matter improved only P-NaHCO3 by 83 %. The effect of nutrient (carbon and nitrogen) addition varied according to different fraction of P. P-NaHCO3 with sorghum incubation seems to be more responsive to nutrient addition. Therefore, minimum tillage with organic and mineral fertilizers amendments has beneficial effect on available P fractions.

Vertical distribution of fertilizer nitrogen from surface water flooding of a silt loam and clay soil used for rice production

AbstractNitrogen (N) fertilizer retention and short‐term vertical redistribution into soil affect N balance and N‐use efficiency in rice (Oryza sativa L.) production systems. A series of experiments was conducted on intact soil cores obtained from rice production fields to track floodwater and soil ammonium‐ and nitrate‐N concentrations up to 96 hr after urea and ammonium sulphate fertilizer amendments to dry, silt loam soil (a) as compared to clay soil, (b) with and without a delay before floodwater establishment and (c) at two initial soil water conditions (dry and muddy). The impact of a 5‐day delay before flood establishment was also compared between untreated and N‐(n‐butyl)thiophosphoric triamide (NBPT)‐treated urea‐N concentrations. Urea‐derived N generally moved deeper into dry, silt loam soil than ammonium sulphate. Ammonium sulphate‐derived N concentration was greatest in the surface 2 cm of soil, decreased with depth, and was unaffected by floodwater duration. A 5‐day delay between fertilization and flooding resulted in urea behaving similarly to ammonium sulphate, although NBPT treatment resulted in vertical N distributions similar to those for untreated urea applied to dry, immediately flooded soil. When urea was applied to muddy soil, no fertilizer N was observed below 2 cm, while large concentrations of ammonium‐N remained in the floodwater. Results collectively demonstrate the importance of immediate downward movement of fertilizer‐applied N into dry soil for retention, and the use of a urease inhibitor to maximize urea‐derived N downward movement into soil when a delay in flood establishment cannot be avoided.

Silicon fertilizers mitigate rice cadmium and arsenic uptake in a 4-year field trial

Comparatively few field experiments have been conducted to monitor the long-term effects of Si fertilizer amendments on the mitigation of Cd and As accumulation in rice grains. A 4-year field trial (eight growing seasons) was established in paddy fields to investigate the effects of different Si fertilizers on the mitigation of Cd and As uptake in rice cultivars. Cultivars for the spring and summer growing seasons were chosen based on their local popularity to investigate the effect of Si fertilizers on different cultivars. Average Cd concentrations in spring rice grains (0.020 ± 0.006 mg/kg) were much lower than those in summer rice grains (0.416 ± 0.370 mg/kg) regardless of rice cultivar. Spring rice grains contained slightly higher average As concentrations (0.43 ± 0.07 mg/kg) than summer rice grains (0.30 ± 0.09 mg/kg). Silicon fertilizers, except sodium silicate, significantly decreased grain Cd concentrations. Calcium silicate fertilizer substantially decreased grain Cd, by up to 55.1 ± 17.6%, and to a greater extent than that in response to Si-potash fertilizer, by up to 26.4 ± 7.9%, probably because of competition between Cd and Ca for Ca transport channels. Slow-release Si fertilizer resulted in the greatest decrease in grain Cd concentration (69.0% ± 8.6%). Slow-release fertilizer may provide a longer-term Si source and higher efficiency of use for rice than readily soluble Si. Silicon fertilizers substantially reduced Cd, but not As, concentrations in summer rice grains for a long term (eight growing seasons). Calcium silicate fertilizer reduced grain Cd concentrations more significantly than potassium silicate fertilizer. Calcium silicate fertilizer exhibited higher efficacy of Cd reduction in grains regardless of rice cultivar or growing season. Slow-release Si fertilizer showed superior ability for Cd mitigation than that of soluble Si fertilizers.

Influence of Poultry Litter Amendment Type and Irrigation Events on Survival and Persistence of Salmonella Newport

Salmonella enterica subsp. enterica serovar Newport is a bacterial foodborne pathogen isolated from several environmental reservoirs on the Delmarva Peninsula and has been associated with several produce-related outbreaks. However, little is known about specific interactions between Salmonella Newport and soil amendments used as fertilizers. The purpose of this study was to determine Salmonella Newport persistence and resuscitation in raw poultry litter (PLR), a common biological soil amendment, and in soils containing poultry litter-based (heat-treated poultry pellets [HTPP]) or chemical fertilizer (urea [U]) amendments to provide equivalent levels of nitrogen to the soil. Inoculated samples were stored in a growth chamber and irrigated regularly over 4 weeks. Soil samples were collected every week for 4 weeks to determine moisture content and surviving Salmonella Newport populations (log CFU per gram dry weight). Data were analyzed by using a one-way analysis of variance and Student's t test. The PLR supported significantly higher (5.07 log CFU/g dry weight [gdw]) populations of Salmonella Newport than HTPP only (1.70 log CFU/gdw). However, PLR-amended (PRLA) soil (2.5 log CFU/gdw) samples had significantly (P < 0.05) lower Salmonella Newport populations compared with HTPP-amended (4.5 log CFU/gdw) and U-amended (4.0 log CFU/gdw) soil samples. The effect of irrigation on Salmonella Newport population levels in PRLA soils was significant, and in a comparative study, the overall increase in the pathogen levels in U-amended soil (mean = 1.12 log CFU/gdw) was significantly greater than that in PLRA soil (mean = 0.54 log CFU/gdw), whereas that in HTPP-amended soil (0.80 log CFU/gdw) was not significantly different from PLRA soil.

Responses of soil enzyme activities and plant growth in a eucalyptus seedling plantation amended with bacterial fertilizers.

Plant growth-promoting rhizobacteria (PGPR) are widely used to improve plant nutrient uptake and assimilation and soil physicochemical properties. We investigated the effects of bacterial (Bacillus megaterium strain DU07) fertilizer applications in a eucalyptus (clone DH32-29) plantation in Guangxi, China in February 2011. We used two types of organic matter, i.e., fermented tapioca residue ("FTR") and filtered sludge from a sugar factory ("FS"). The following treatments were evaluated: (1) no PGPR and no organic matter applied (control), (2) 3 × 109CFU/g (colony forming unit per gram) PGPR plus FS (bacterial fertilizer 1, hereafter referred to as BF1), (3) 4 × 109CFU/g plus FS (BF2), (4) 9 × 109CFU/g plus FS (BF3), (5) 9 × 109CFU/g broth plus FTR (BF4). Soil and plant samples were collected 3months (M3) and 6months (M6) after the seedlings were planted. In general, bacterial fertilizer amendments significantly increased plant foliar total nitrogen (TN) and soil catalase activity in the short term (month 3, M3); whereas, it significantly increased foliar TN, chlorophyll concentration (Chl-ab), proline; plant height, diameter, and volume of timber; and soil urease activity, STN, and available N (Avail N) concentrations in the long term (month 6, M6). Redundancy analysis showed that soil available phosphorus was significantly positively correlated with plant growth in M3, and soil Avail N was negatively correlated with plant growth in M6. In M3, soil catalase was more closely correlated with plant parameters than other enzyme activities and soil nutrients, and in M6, soil urease, polyphenol oxidase, and peroxidase were more closely correlated with plant parameters than other environmental factors and soil enzyme activities. PCA results showed that soil enzyme activities were significantly improved under all treatments relative to the control. Hence, photosynthesis, plant growth, and soil N retention were positively affected by bacterial fertilizer in M6, and bacterial fertilizer applications had positive and significant influence on soil enzyme activities during the trial period. Thus, bacterial fertilizer is attractive for use as an environmentally friendly fertilizer in Eucalyptus plantations following proper field evaluation.

Optimal agricultural spreading scheduling through surrogate-based optimization and MINLP models

The most commonly used definition of climate smart agriculture (CSA) is provided by the Food and Agricultural Organisation of the United Nations, which defines CSA as “agriculture that sustainably increases productivity, enhances resilience, reduces/removes greenhouse gas where possible, and enhances achievement of national food security and development goals”. In this definition, the principal goal of CSA is identified as food security and development, while productivity, adaptation, and mitigation are identified as the three interlinked pillars necessary for achieving this goal. In the context provided by the CSA, soils are seen as a lever to improve the carbon footprint of agriculture, namely through their role as carbon sinks. Improving soils and in particular agricultural soils’ content in soil organic carbon (SOC) in one of the measures enabling to improve the environmental impact of agricultural practices. In this context, composts can be seen as an important feedstock for sustainable farming. To support the development of organic amendment strategies enabling to increase soils’ SOC content, this work proposes a novel methodology to optimize the monthly scheduling of composts and mineral fertilizers amendments. The schedule proposed maximizes soil health - via improved SOC content - while ensuring optimal gross operating surplus from agriculture. This problem is subjected to certain operational, regulatory and soil-dynamics constraints which leads to a complex optimization problem and has to be solved in a relatively short time period for decision-making purposes. This is a nonlinear optimization problem (NLP) which is based on a soil-simulation model from which the analytic functions are not explicitly available for the optimization model. Operational and regulatory constraints are explicitly defined and integer and continuous variables are needed in the modeling. In order to effectively solve it in a deterministic way, a novel surrogate-modeling approach for the objective functions and constraints is proposed. Another novelty comes from the implementation of a continuous-variable-reduction procedure in order to build effective surrogates. The optimisation model results obtained from a real case study show that local optimal solutions can be identified with short computation times. The evaluated scenario shows that the optimized strategy could increase by 8% the carbon in soil after 13 years while increasing by 7% the estimated agricultural profit when compared to expert based application schedules.