Lucy Ngatia

By Lucy Ngatia and Robert Taylor

Phosphorus (P) eutrophication in the aquatic system is a global problem. With a negative impact on health industry, food security, tourism industry, ecosystem health and economy. The sources of P include both point and nonpoint sources. Controlling P inflow from point sources to aquatic systems have been more manageable, however controlling nonpoint P sources especially agricultural sources remains a challenge. The forms of P include both organic and inorganic. Runoff and soil erosion are the major agents of translocating P to the aquatic system in form of particulate and dissolved P. Excessive P cause growth of algae bloom, anoxic conditions, altering plant species composition and biomass, leading to fish kill, food webs disruption, toxins production and recreational areas degradation. Phosphorus eutrophication mitigation strategies include controlling nutrient loads and ecosystem restoration. Point P sources could be controlled through restructuring industrial layout. Controlling nonpoint nutrient loads need catchment management to focus on farm scale, field scale and catchment scale management as well as employ human intervention which includes ferric dosing, on farm biochar application and flushing and dredging of floor deposits. Ecosystem restoration for eutrophication mitigation involves phytoremediation, wetland restoration, riparian area restoration and river/lake maintenance/restoration. Combination of interventions could be required for successful eutrophication mitigation.

Part of the book: Phosphorus

By Lucy W. Ngatia, Johnny M. Grace III, Daniel Moriasi, Alejandro Bolques, George K. Osei and Robert W. Taylor

Phosphorus (P) eutrophication in the water bodies is of global concern. The role of biochar in the mitigation of (P) eutrophication has recently received substantial attention. Agriculture is the main source of P in the water bodies, as a result of excessive fertilizer and manure application. Excessive P results in excessive primary production in the water bodies, leading to anoxic conditions, growth of toxic algae blooms, altering plant species composition and biomass. Therefore, resulting in food web disruption, fish kill, toxins production and recreation areas degradation. When biochar is applied on farm, it has potential to sorb/adsorb P, immobilizing it, slowing its translocation to the water bodies. However, biochar effectiveness in P sorption is influenced by both feedstock type and pyrolysis temperature. The interaction between feedstock type and pyrolysis temperature influences the biochar pH, surface area, aromatic carbon, cation exchange capacity, surface charge density, biochar internal porosity and polar and nonpolar surface sites that promote nutrient absorption. Hence, biochar properties have a broad spectrum that influences how biochar reacts with P sorption; therefore, it is not appropriate to extrapolate observed results to different materials. Biochar that promote P sorption rather than desorption should be considered and designed to meet specific management practices.

Part of the book: Biochar

By Lucy Ngatia, Johnny M. Grace III, Daniel Moriasi and Robert Taylor

Nitrogen (N) and phosphorus (P) eutrophication in marine ecosystems is a global problem. Marine eutrophication has a negative impact on food security, ecosystem health and economy through disruptions in tourism, fisheries and health industries. Both N and P have known point and non-point sources. Control of point sources has been easier than non-point sources particularly agricultural sources for both N and P as well as fossil fuel combustion for N, which remains a major challenge. Implementing mitigation strategies for N has been reported to be effective for P mitigation; however, the converse is not true due to mobility and volatility of N. Excessive N and P cause algae blooms, anoxic conditions, and ocean acidification with these conditions leading to dead zones, fish kill, toxin production, altered plant species diversity, food web disruption, tourism disruption and health issues. Management of N and P pollution includes reduction of leaching from farms through crop selection, timely and precise application of fertilizer and building artificial wetlands, proper management of animal waste, reduction of fossil fuel N emission, mitigating N and P from urban sources and restoration of aquatic ecosystem. Mitigation measures need to focus on dual nutrient strategy for successful N and P reduction.

Part of the book: Monitoring of Marine Pollution

By Lucy W. Ngatia, Daniel Moriasi, Johnny M. Grace III, Riqiang Fu, Cassel S. Gardner and Robert W. Taylor

Soil organic carbon (SOC) is a major indicator of soil health. Globally, soil contains approximately 2344 Gt of organic carbon (OC), which is the largest terrestrial pool of OC. Through plant growth, soil health is connected with the health of humans, animals, and ecosystems. Provides ecosystem services which include climate regulation, water supplies and regulation, nutrient cycling, erosion protection and enhancement of biodiversity. Global increase in land use change from natural vegetation to agricultural land has been documented as a result of intensification of agricultural practices in response to an increasing human population. Consequently, these changes have resulted in depletion of SOC stock, thereby negatively affecting agricultural productivity and provision of ecosystem services. This necessitates the need to consider technological options that promote retention of SOC stocks. Options to enhance SOC include; no-tillage/conservation agriculture, irrigation, increasing below-ground inputs, organic amendments, and integrated, and diverse cropping/farming systems. In addition, land use conversion from cropland to its natural vegetation improves soil C stocks, highlighting the importance of increasing agricultural production per unit land instead of expanding agricultural land to natural areas.

Part of the book: Environmental Health

By Samuel O. Oluwayemi and Lucy W. Ngatia

Cadmium (Cd) is known as a very toxic heavy metal that can accumulate in soils through natural processes and human activities, particularly with the use of phosphate fertilizers, manure, and industrial emissions. It can persist and mobilize through soil solutions, allowing it to be absorbed by crops used in poultry feed formulations. Different parameters, such as soil pH, organic matter content, and climatic conditions, play an integral role in determining the bioavailability of Cd. Its absorption by feed crops in varying concentrations directly affects feed quality and growth performance in chickens fed such contaminated feed. Bioaccumulation, resulting from the long-term intake of contaminated feed by poultry, causes Cd to accumulate in their organs (liver and kidneys) and edible tissues (meat and eggs). Health risks, such as kidney damage, bone demineralization, and the growth of cancerous cells, are likely to arise in humans through the consumption of these products – a process known as biomagnification – as Cd moves up the food chain. Therefore, soil- and feed-based interventions are necessary to reduce the risk of Cd contamination. The addition of biochar, lime, and phytoremediation strategies helps reduce the bioavailable forms of Cd in soils. Supplementing poultry feed with minerals (zinc and selenium) and adsorbents (zeolite and bentonite) also helps reduce Cd absorption in poultry. Overall, the mitigation approaches ensure food safety and security, aligning with the One Health principle by safeguarding the health of animals, humans, and the environment.

Part of the book: Contaminated Soils - Remediation Technologies for Sustainable Environment [Working title]

By Tithi Sarker and Lucy W. Ngatia

Phosphorus (P) is one of the most essential nutrients for rice growth. Yet, its availability is often extremely limited in many rice-growing regions due to strong phosphorus fixation in the soil. In areas with flooded paddy fields, phosphorus commonly reacts with iron (Fe), aluminum (Al), and calcium (Ca) minerals. These chemical reactions result in the formation of insoluble compounds, which are nonnutritious to rice roots. The continuous flooding and draining cycles of rice fields further intensify P fixation. Additionally, alternating reducing and oxidizing conditions, along with regenerating fresh iron oxides, tightly bind phosphate to the soil. Consequently, only a small portion of the phosphorus contained in the fertilizer becomes available to crops. This leads to a reduction in rice productivity, and an increase in the use of fertilizer. This may ultimately create a risk of food scarcity for communities that rely on rice. Also, excessive application of fertilizer often leads to environmental problems. For example, it can cause runoff and eutrophication of nearby water bodies. This work examines the primary causes, mechanisms, and consequences of phosphorus fixation in paddy field soils and assesses sustainable strategies to enhance its availability. Several management strategies exist that potentially reduces phosphorus fixation and improve the effectiveness of fertilizers. The most commonly used methods include soil amendments, biological approaches, and improved practices for managing fertilizers and water. Understanding and analyzing these methods are crucial for the development of sustainable rice production and enhanced food security, while also protecting the environment and improving soil health.

Part of the book: Agroecosystems - Principles and Practices [Working title]

By Sandreika O. Laird and Lucy W. Ngatia

Southern Pine Beetles (SPB) are economically important insect pests of the pine forest industry, causing significant losses of forest cover estimated at over US$1.7 billion to the US national economy within 14 years. The loss of forest cover increases the amount of bare land, making it more susceptible to erosion and nutrient leaching. Previous studies have indicated that their effects extend beyond forest cover loss to soil health, with either a positive or negative impact. For instance, N-rich needles drop off, and the litter pile increases N and C mineralization. Thus, tree death leads to a temporary increase in soil nutrients due to reduced uptake, increased soil moisture from lower evapotranspiration, and redistribution of nutrients. Additionally, SPB selectively kills less productive trees to reduce competition for resources and stimulate forest productivity. However, the decomposition of the litter pile doubles mineral soil heterotrophic respiration and increases Greenhouse gas emissions. Pathogenic fungi communities increase at the expense of beneficial mycorrhizae communities. Moreover, reductions in forest cover and canopy negatively affect C sequestration, evapotranspiration, and plant water uptake. Therefore, it is essential to understand the mitigation strategies required for sustainable forest management. Generally, the Integrated Pest Management approach is recommended for managing SPB infestations. A continuous pest surveillance program using recommended traps and lures helps determine the level of SPB infestation. Other management strategies discussed in this document are useful depending on the SPB threshold level. It is recommended that future studies explore the effectiveness of some entomopathogenic fungi and other management strategies.

Part of the book: Forest Science and Ecosystem Sustainability