This study was conducted to assess the effects of amending tropical sandy soils with biochar derived from agro-industrial wastes on the leaching and utilization of nitrogen (N) by maize. The experiment was conducted in pots in a greenhouse with two sandy soil types and two different biochars. The biochars used in this experiment were preselected in a preliminary column experiment that assessed the N retention capacities of the different biochars and those that exhibited the best retention capacities chosen for experimentation. The biochars evaluated included saw dust, rice husk and corncob pyrolyzed at 500 °C and the results from the column leaching experiment showed that sawdust biochar had superior retention capacities for both NO3− and NH4+, followed by rice husk biochar. The pot experiment utilized sawdust and rice husk biochars applied at rates of 0, 20 and 40 t/ha to the soil treated with different N sources including cow dung and ammonium sulfate and growing maize on the amendments for two seasons with each season lasting for five weeks. The soils were leached on the 14th and 28th days after planting to determine the amount of leachable N. Biochar amendments reduced the leaching of NO3−N and NH4+N with no significant differences observed between biochar types, but between soil types. The abatement of leaching by biochar amendments consequently enhanced N uptake by maize and dry matter production and thus, agro-industrial waste biochar amendment is recommended for reducing leaching in tropical sandy soils.

This study aimed to monitor the changes in the content and types of nitrogen (N) and phosphorus (P) in swine slurry (SS) across three aerobic digestion processes in public livestock recycling centers. In total, 148 swine slurry samples, including raw swine slurry from the three digestion cells, were collected from 37 livestock recycling centers around Korea from early April to mid-July 2020. The physical and chemical characteristics including the total N and P and various types of N and P of the samples were determined. The contents of organic N and P were calculated as the difference between the total and mineral components of N and P. The results showed that solid separation and aerobic digestion of SS significantly reduced the amount of the total N in the effluent by almost 70.1%, but only reduced the total P by 0.17%, resulting in a significant reduction of available N and a very high P:N ratio. This study confirmed that continuous application of composted liquid swine slurry based on N content may lead to the overapplication of P. Therefore, further research is needed to improve the N content and lower the high P:N ratios.

Biochar's capacity to abate NH3 emissions from fertilised agricultural soils may be enhanced through both modifications and formulation of slow-release biochar-based N fertilisers but there is a dearth of data in this area. Sulphuric acid (H2SO4), hydrogen peroxide (H2O2) and potassium hydroxide (KOH) were used to modify biochars which are denoted as BSAD, BHPO and BKOH, respectively. Nitrogen (N) enrichment was performed using urea and ammonium nitrate and the enriched biochars are denoted as BUR and BAN, respectively. The biochars were characterised by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The ammonia abatement potentials of both the modified and N-enriched biochars were assessed in the incubation experiments which lasted for 30 days. Urea was used as a control while non-modified biochar (PrBC) was included for comparison. Compared to the control, PrBC, BKOH, BHPO, BSAD, BUR and BAN attenuated gaseous NH3 emissions by 57.62%, 63.06%, 73.23% and 74.85%, 79.93% and 82.88%, respectively. Biochar modifications increased the content of oxygen containing surface groups especially carboxyl and sulphoxide in the case of BSAD as depicted from the instrumental analysis data, which most probably increased the sorption of NH3 and its transformation to nitrates thus, resulting in a higher NH3 abatement capacity than that of PrBC. XPS data indicated that N-enrichment resulted in reactions of N with the surface groups of biochar which slowed its release, concomitantly lowering NH3 volatilisation better than even the modified biochars.

It has been demonstrated that biochar has a great potential to reduce volatilisations of ammonia (NH3) from fertilised agricultural soils. While there have been several laboratory studies to demonstrate the effects of biochar on gaseous NH3 emissions, there is hardly any data on the influence of biochar amendments on NH3 volatilisations from the soils under a field environment. Modifying biochar or enriching it with nitrogen (N) may maximise its capacity to abate gaseous NH3 emissions from the soil. Three biochars, i.e. SAB, HPB, and KHB modified through post-pyrolysis treatment with sulphuric acid, hydrogen peroxide, and potassium hydroxide, respectively as well as two biochars enriched with either molten urea (URB) or ammonium nitrate (ANB), were used alongside the pristine biochar (PRB) for comparisons. The quantity of gaseous NH3 evolved from each the biochar amendments including their effects on the growth and yield of the Chinese cabbage plus selected soil chemical properties were evaluated through a field experiment. The control experiment consisted of urea applied alone. In comparison with the control, PRB, KHB, HPB, SAB, URB, and ANB amendments abated NH3 volatilisations from the soil by 44.18%, 45.91%, 63.23%, 65.62%, 72.66%, and 76.71%, respectively. Additionally, PRB, SAB, KHB, HPB, ANB, and URB amendments increased Chinese cabbage yields by 138.5%, 172.0%, 117.3%, 181.1%, 194.0%, and 181.1%, respectively in comparison with the control. The strong linear relationship (r(2) = 0.97) between cumulative NH3 emissions and nitrogen use efficiencies indicates that biochar-induced reductions in emissions of gaseous NH3 concomitantly increased the use-efficiencies of the applied N.

There is a paucity of data regarding the effect of nutrient-enriched biochar amendments on nutrient dynamics in both soil and crops. This is important because unlike pristine biochar, nutrient-enriched biochar is applied to the soil in minute quantities as large amounts may led to over application of the nutrients loaded in it. The current study examined the effects of both phosphorus- and nitrogen-enriched biochars on the dynamics of both macro and micronutrients in the sandy soil and leaf lettuce grown thereon. The phosphorus enrichment followed co-pyrolysis of animal manure (cow dung) with 25% and 50% bone meal (w/w), while the nitrogen enrichment was achieved by soaking the co-pyrolyzed biochar into urea and urea-hydrogen peroxide. The performances of the nutrient-enriched biochar were compared with the conventional amendment of urea and triple superphosphate (TSP) in the production of leaf lettuce over a period of two seasons in a pot experiment. The nutrient-enriched biochar amendments resulted into higher microbial biomass carbon and carbon to nitrogen ratios than the conventional amendment. The conventional amendment caused more phosphorus, potassium, and magnesium accumulations in the leaf lettuce than the nutrient-enriched biochar amendments. The nutrient-enriched biochar amendments led to more accumulations of nitrogen, calcium, and micronutrient elements in the leaf lettuce and availabilities of all the nutrient elements in the soil and thus, nutrient-enriched biochar acted as a reservoir that could provide nutrients to the growing lettuce beyond a single growing season.

Loss of organic matter and related loss of soil microbial diversity and activity, as a result of intensive agriculture has contributed to an increase in soil borne plant diseases.Sweet pepper is highly susceptible to many soil borne diseases such as damping-off, root rots and wilts.In view of this, the study was conducted to assess the influence of different growth media on sweet pepper in terms of growth, yield and incidence of diseases.Materials used include: Seeds of two varieties of sweet pepper (Yolo wonder and California Wonder), rice husk, coconut hull, sawdust, groundnut hull, sugarcane bagasse, top soil and well cured cow dung.The Soilless media were prepared by mixing it with cow dung in a ratio of 20:1, whilst the cow dung was applied to the top soil at a rate of 100 kg N/ha.The experiment was a two by six (2˟6) factorial experiment with twelve (12) treatments replicated three (3) times resulting in a total of thirty six (36) treatments laid out in Complete Randomised Design (CRD).Parameters measured include; plant height, number of leaves per plants, number of fruits per plant, fruit length, fruit diameter and incidence of root rot and wilt diseases.The results on plant heights at various weeks after transplanting showed that, all the soilless media generally, produced plants with significantly higher height at (p ˂ 0.05) than the top soil.The results also showed that, the soilless media had superior number of leaves and fruits produced per plant, fruit length and diameter to that of the top soil.There were no incidence of root rot and wilt diseases in the soilless media but the top soil had two incidence of wilt disease.The results reveals that, cultivation of sweet pepper in soilless medium can give you better growth and yield and can also reduce the occurrence of soil borne diseases like root rot and wilt in sweet pepper.Therefore, cultivation of sweet pepper in soilless medium should be encourage to reduce the occurrence of soil borne diseases in other to enhance growth and yield in sweet pepper.