Dr. ISAAC MPANGA

In this meta-analysis, however, the results obtained from all experiments within the project are included. Therefore, it is free of publication bias. In contrast to reviews of published literature, our unique study design is based on a common standardized protocol which applies to all experiments conducted within the project to reduce sources of variability. Based on data of crop growth, yield and P acquisition, we conclude that application of BEs can save fertilizer resources in the future… Show more

In this meta-analysis, however, the results obtained from all experiments within the project are included. Therefore, it is free of publication bias. In contrast to reviews of published literature, our unique study design is based on a common standardized protocol which applies to all experiments conducted within the project to reduce sources of variability. Based on data of crop growth, yield and P acquisition, we conclude that application of BEs can save fertilizer resources in the future, but the efficiency of BE application depends on cropping systems and environments. Show less

Climate change is upon us, and we need to act now in our own small ways without waiting for anyone. In this book, Dr Mpanga (a farmer, teacher, research, and consultant with expertise in sustainable and regenerative agriculture systems) presents a comprehensive guide of circular agriculture principles and practices as a climate-smart tool for resilient communities, cities, economies, and food security while ensuring responsible stewardship of the planet for future generations. He illustrated… Show more

Climate change is upon us, and we need to act now in our own small ways without waiting for anyone. In this book, Dr Mpanga (a farmer, teacher, research, and consultant with expertise in sustainable and regenerative agriculture systems) presents a comprehensive guide of circular agriculture principles and practices as a climate-smart tool for resilient communities, cities, economies, and food security while ensuring responsible stewardship of the planet for future generations. He illustrated how a hierarchical implementation model will help linear agricultural and economic systems transition to circularity with critical consideration of all stakeholders, their goals, and resources. Also, the role of waste management, agrivoltaic, biofertilizers, livestock, and other regenerative agricultural practices are discussed with practical demonstrations and illustrations that makes the subject easy to comprehend.
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Background
Grape pomace (GP) is a by-product of wineries after filtering the grape juice for wine production. GP contains seeds, pulp, skin, and stalks with acidic properties, and it is normally composted before using as a soil amendment. However, composting GP requires more time, labor, and equipment; furthermore, composting loses some of the desirable organic acids for arid soils. The acidic properties of these organic acids and the plant nutrients in GP make it a desirable amendment for… Show more

Background
Grape pomace (GP) is a by-product of wineries after filtering the grape juice for wine production. GP contains seeds, pulp, skin, and stalks with acidic properties, and it is normally composted before using as a soil amendment. However, composting GP requires more time, labor, and equipment; furthermore, composting loses some of the desirable organic acids for arid soils. The acidic properties of these organic acids and the plant nutrients in GP make it a desirable amendment for arid soils in both non-composted and composted forms.

Aim

This study investigates the potential of directly applying GP as a soil amendment and its impact on arid soil health and plant performance.

Methods

To test the potential of non-composted GP as a soil amendment, greenhouse and field studies were conducted by combining GP with existing management practices (manure application for soil used in the greenhouse study and fertigation for the field study) to assess the effects of GP on soil health and crop (maize, wheat, and grape) performance.

Results

Adding 5% GP to an alkaline soil significantly increased maize and wheat growth and shoot nutrient concentrations in the greenhouse and grapes in the field (48% yield increase). The significance of GP on maize, wheat, and grapes was associated with soil nutrient enhancements (i.e., nutrients supplied, increase in organic matter and microbial biomass increase, reduction in pH, and better nutrient mobilization).

Conclusion

GP has the potential for direct use as a soil amendment for soil and crop health improvement, especially in arid soils with high pH and limited soil organic matter. Show less

Agriculture continues to be a major consumer of global water with increasing demand in the sector due to increasing human population and extreme climate events (increasing temperature and severe drought) in most regions. These human and natural factors continually cause water distress by increasing water risk areas (limited water for agricultural use) around the globe over the past decades and threaten food production in most regions. It is clear that innovations that strategically enhance… Show more

Agriculture continues to be a major consumer of global water with increasing demand in the sector due to increasing human population and extreme climate events (increasing temperature and severe drought) in most regions. These human and natural factors continually cause water distress by increasing water risk areas (limited water for agricultural use) around the globe over the past decades and threaten food production in most regions. It is clear that innovations that strategically enhance water use efficiencies in agricultural systems are required more than ever to sustain current and future food production for our growing population. This chapter elaborates some strategies used in agriculture to manage water use for food, feed, and fiber production. Some of the strategies discussed include soil health practices, irrigation methods, water harvesting, steep and slope management, precision agriculture, wastewater management, and biotechnology/breeding programs. Research and extension programs continue to help promote their wide use, but more sectoral efforts are required to help promote adoptions in practical areas. Show less

Maize is one of the globally most important cereal crops used for food, feed and fuel. It requires optimum soil nutrients such as Nitrogen (N), Phosphorus (P), and Potassium (K) for proper growth and development as well as for tolerance to biotic and other abiotic stresses. Yield potentials are not met under suboptimal soil fertility. One of the innovations that can reduce environmental impacts of continuous fertilization and lower the cost of maize production under low soil nutrient conditions… Show more

Maize is one of the globally most important cereal crops used for food, feed and fuel. It requires optimum soil nutrients such as Nitrogen (N), Phosphorus (P), and Potassium (K) for proper growth and development as well as for tolerance to biotic and other abiotic stresses. Yield potentials are not met under suboptimal soil fertility. One of the innovations that can reduce environmental impacts of continuous fertilization and lower the cost of maize production under low soil nutrient conditions is the development and use of tolerant cultivars. This paper provides spotlights on the following: (1) morphology and physiology of root and shoot systems; (2) genetics and genomics; and (3) transcriptome, proteome, and metabolome profiles, to elucidate maize tolerance to low amounts of soil nutrients, N, P, and K. Maize cultivars having deeper rooting structure, more lateral roots, dense roots, and high root exudates are more tolerant to N, P, and K limited conditions. Cultivars that are tolerant to N, P, and K stress (low) have high nutrient use efficiency, good photosynthetic and translocation activity that support high aboveground shoot weight under suboptimal N, P, and K conditions. Maize tolerance to N, P, and K stress (low) is quantitative, and mainly controlled by additive genes. Maize cultivar development and dissemination programs can exploit the mechanisms highlighted in this review. Show less

The need to reduce the negative impacts of agriculture on the environment and the consumer demands for food produced without synthetic chemical inputs have led to organic agriculture production systems. The United States (US) commands about half of the market share of organic products worldwide and is home to half of the world's organic farmers, but limited information is available on trends of on-farm land-use practices and challenges in organic crop production systems. This study utilizes the… Show more

The need to reduce the negative impacts of agriculture on the environment and the consumer demands for food produced without synthetic chemical inputs have led to organic agriculture production systems. The United States (US) commands about half of the market share of organic products worldwide and is home to half of the world's organic farmers, but limited information is available on trends of on-farm land-use practices and challenges in organic crop production systems. This study utilizes the agricultural production surveys from the United States Department of Agriculture (USDA) from 2008 to 2019 to investigate state and national trends in organic farm area, number, and sales, and to evaluate national trends in on-farm land-use practices and challenges facing US organic production. From 2008 to 2019, the number of certified organic farms, land area, and sales increased by 5, 6, and 12%, respectively. The use of green and animal manures is the most common land-use practice in certified organic crop production systems. The number of farms using the on-farm organic practices remained the same or increased steadly except organic mulch/compost which declined. However, all the practices declined proportionally, except rotational grazing which recorded an increase in 2019. The most significant primary challenges faced by certified organic farmers are related to regulations of organic practices and production costs which worsen over time. United States certified organic production has the potential for expansion in terms of farm numbers, land area, markets, and increased adoption of regenerative agricultural practices. However, for this to occur, efforts involving farm-level research and policy reviews with direct farmer involvement are needed to address these primary challenges facing organic farmers. Show less

Synthetic nitrogen fertilizer use comes with unsustainable financial and environmental costs, making it not attractive to small-scale and organic farmers. Poultry manure (PM) when available is a primary fertilizer source for small-scale and organic farmers but there is still limited research on its effects of specific crops and soil fertility under specific practices. The study investigated PM effects on garden egg in three seasons in Ghana and PM effects soil fertility in sandy-loam soils of… Show more

Synthetic nitrogen fertilizer use comes with unsustainable financial and environmental costs, making it not attractive to small-scale and organic farmers. Poultry manure (PM) when available is a primary fertilizer source for small-scale and organic farmers but there is still limited research on its effects of specific crops and soil fertility under specific practices. The study investigated PM effects on garden egg in three seasons in Ghana and PM effects soil fertility in sandy-loam soils of Arizona after three years under flood irrigation and no-till. The PM application improved garden egg growth (dry matter by 73%) and increased yield by 66% in slightly acidic sandy-loam tropical soils, which could be related to soil mineral improvement. In the semi-arid soil, three years PM application increased cation exchange capacity (41%), P (471%), K (18%), S (244%), Ca (45%), Mg (31%), Zn (5%) and Mn (19%) with reduction in nitrate (− 26%), Fe (− 38%) and Cu (− 11%). The reduction in the nitrate and Fe in the semi-arid Arizona cropland could be associated to flood irrigation and high soil pH, respectively. To gain the full potential from PM applications, best management practice is recommended to reduce nitrate leaching. Show less

The demand for agricultural lands for other uses because of population growth and extreme climate in Arizona led to 57% decrease in average farm size and 127% increase in farm numbers from 1997 to 2017, which threaten sustainable local food production. Small-scale family farms of less than 10 acres make up 50% of the farmer population in the state and have a vital role in resilient and sustainable practices that maximize land use with less negative impact on the environment. This study… Show more

The demand for agricultural lands for other uses because of population growth and extreme climate in Arizona led to 57% decrease in average farm size and 127% increase in farm numbers from 1997 to 2017, which threaten sustainable local food production. Small-scale family farms of less than 10 acres make up 50% of the farmer population in the state and have a vital role in resilient and sustainable practices that maximize land use with less negative impact on the environment. This study investigated land use and farm practices among small-scale growers in north-central Arizona in their resilience in sustainable food production. The finding revealed 52% of the small farms are family operations with dominant regenerative and sustainable practices (27% cover cropping, 26% compost, 23% crop rotation, 22% animal and green manure, 21% no-till, and 18% reduced tillage) with less interest in conventional practices (5% intensive tillage and 13% synthetic fertilizers). Ninety-five percent of the growers used biological, cultural, or mechanical practices for weed, pest, and disease control , while only 5% used conventional synthetic chemicals. For water use, 78% of the growers used water-saving irrigation practices (drip, subsurface, and sprinklers), while 11% used open flood irrigation. Driving forces for the sustainable practices among the small-scale growers are their consumers (community supported agriculture, restaurants, Farmers' Markets, and farm stands) and extreme climate conditions. Small-scale growers have great potential in advancing resilient, environmentally friendly practices for sustainable local food production and environmental stewardship. Show less

Irrigation water is crucial for farm operations in the world, with irrigated lands contributing about 40% to food and fiber production. In the Southwestern United States, the demand for irrigation water has increased due to population growth, rising temperatures, and severe drought events in the region. Irrigation plays a vital role in the economies of southwestern states and requires comparative studies to understand the current situation and propose possible improvement strategies. This study… Show more

Irrigation water is crucial for farm operations in the world, with irrigated lands contributing about 40% to food and fiber production. In the Southwestern United States, the demand for irrigation water has increased due to population growth, rising temperatures, and severe drought events in the region. Irrigation plays a vital role in the economies of southwestern states and requires comparative studies to understand the current situation and propose possible improvement strategies. This study investigated the trend of irrigated cropland, the quantity of irrigation water use, irrigation technology, scheduling decisions, and irrigation outreach using data from 2007 and 2017 United States Department of Agriculture (USDA) National Agriculture Statistics Service (NASS) census. Harvested cropland in the region remained the same with minimal increase in total irrigated land (1%) and the quantity of irrigated water used (2%). However, gravity irrigation methods reduced significantly by 12%, with a 71% increase in the use of drip irrigation systems. The increase in the adoption of soil moisture sensors (55%), plant sensors (107%), government schedules (29%), and supplier’s schedules (50%) for irrigation scheduling decisions, did not translate to a reduction in irrigation water use at the regional level. However, at the state level within the same period, Arizona recorded an increase in irrigated cropland by 10% and harvested cropland by 9%, with a reduction in the quantity of irrigation water used (-5%). The gains in Arizona could be associated with the combined effects of improved irrigation technologies and the use of best management decisions, which could serve as a model for prudent water use in the southwest. There is a need to increase the effort in science-based education and extension programming on integrated approaches that emphasize both irrigation technology and the best management practices, which include seed selection for drought-tolerant crops. Show less

Aims
The use of plant growth-promoting micro-organisms (PGPMs) to improve plant-nutrient acquisition has a long history but reproducibility remains a challenge. Recent findings suggest an important role of suitable inoculant-fertilizer combinations for the expression of PGPM-effects, particularly with respect to nitrogen (N) supply. In face of the well-documented N form effects on rhizosphere pH, this study addressed the impact of ammonium-assisted PGPM-interactions on the acquisition of… Show more

Aims
The use of plant growth-promoting micro-organisms (PGPMs) to improve plant-nutrient acquisition has a long history but reproducibility remains a challenge. Recent findings suggest an important role of suitable inoculant-fertilizer combinations for the expression of PGPM-effects, particularly with respect to nitrogen (N) supply. In face of the well-documented N form effects on rhizosphere pH, this study addressed the impact of ammonium-assisted PGPM-interactions on the acquisition of sparingly soluble calcium-phosphates as affected by soil pH.

Methods and Results
The effects of stabilized ammonium fertilization combined with the PGPM inoculant Bacillus amyloliquefaciens FZB42 on the acquisition of rock phosphate in maize were examined on two soils (moderately acidic-pH 5·6 and alkaline-pH 7·8). On the two contrasting soils, FZB42 improved the P status and promoted plant growth by different mechanisms. On the acidic soil, a combination of ammonium-fertilization with FZB42 increased P-acquisition by Rock P solubilization via rhizosphere acidification but P-supply in the noninoculated control was already sufficient to meet the plant demands. By contrast, on the alkaline soil, plant growth-promotion was associated with FZB42-induced root growth stimulation.

Conclusion
The results suggest a significant impact of soil pH on performance and the mode of action of PGPM inoculants, to be considered for practical applications. Show less

Climate variability is a major factor threatening crop production in Arizona State. However, limited information exists on how growers are adapting with land-use practices. Using data from the National Oceanic and Atmospheric Administration and the Agricultural Census (2012 and 2017) of the US Department of Agriculture, this study investigates trends of land-use practices among small- and large-scale growers and their possible effects on harvested cropland. From 2012 to 2017, there are… Show more

Climate variability is a major factor threatening crop production in Arizona State. However, limited information exists on how growers are adapting with land-use practices. Using data from the National Oceanic and Atmospheric Administration and the Agricultural Census (2012 and 2017) of the US Department of Agriculture, this study investigates trends of land-use practices among small- and large-scale growers and their possible effects on harvested cropland. From 2012 to 2017, there are reductions in total farmlands (−0.5%) and vegetable production lands (−4%) with varying temperatures, precipitation, and drought severity index. However, harvested crop- and vegetable land increased by 3% and 11%, respectively, which was mainly influenced by large-scale growers. This coincided with an increase in sustainable land-use practices such as conservation agriculture no-till (103%), reduced tillage (71%), and cover cropping (123%) which are most popular among large-scale growers. Manure application also increased by 30%. However, there were reductions in other practices such as intensive tillage (−9%), use of commercial fertilizers (−0.2%), nematicides (−63%), and chemical diseases control (−16%). Unfortunately, non-sustainable practices (irrigation, insecticide, and herbicide application increased by 27%, 39%, and 10%, respectively. This study reveals potential benefits of sustainable agricultural practices in Arizona and a need for increased adoption among small-acreage growers. Show less

Taken together, the thesis demonstrated that the selection of compatible combinations of fertilizers and PGPM inoculants is an essential factor for the successful establishment of beneficial plant-PGPM interactions in the rhizosphere. Combinations with stabilized ammonium fertilizers or with products based on organic waste recycling, such as composted manures, have been identified as two promising examples with potential for the development of PGPM-assisted production systems.

The combination of the bacterial inoculants Pseudomonas sp. DSMZ 13134 (Proradix) and Bacillus amyloliquefaciens FZB42 with ammonium sulphate fertilization, stabilized with the nitrification inhibitor 3,4‐dimethylpyrazole‐phosphate (DMPP), resulted in a superior shoot biomass production (79–111%) and shoot P accumulation (109–235%) as compared with nitrate supply. This effect could be partially attributed to (1) ammonium‐induced rhizosphere acidification via increased root extrusion of protons,… Show more

The combination of the bacterial inoculants Pseudomonas sp. DSMZ 13134 (Proradix) and Bacillus amyloliquefaciens FZB42 with ammonium sulphate fertilization, stabilized with the nitrification inhibitor 3,4‐dimethylpyrazole‐phosphate (DMPP), resulted in a superior shoot biomass production (79–111%) and shoot P accumulation (109–235%) as compared with nitrate supply. This effect could be partially attributed to (1) ammonium‐induced rhizosphere acidification via increased root extrusion of protons, (2) promotion of root hair elongation, and (3) increased shoot concentrations of hormonal growth regulators (indole‐3‐acetic acid, zeatin, gibberellic acid). The effects, induced by the microbial inoculants were mainly related to increased root length development (43–44%), associated with a 60% increase in auxin production potential. No inoculant effects were detected on root hair elongation or on chemical modifications of the rhizosphere involved in P solubilisation, such as rhizosphere acidification, release of carboxylates or secretory phosphohydrolases. However, the ammonium‐induced stimulation of root hair elongation increased preferential sites for root colonization by the selected inoculants, which may explain the increase in rhizosphere abundance of PGPMs, exemplarily recorded for the fungal inoculant Trichoderma harzianum OMG16 (210%). The presented data suggest a network of positive interactions between stabilized ammonium fertilization and plant growth‐promoting functions of various bacterial and fungal PGPM inoculants. This offers perspectives to increase the efficiency and the reproducibility of PGPM‐assisted fertilization strategies. Show less

This study demonstrates that the form of nitrogen fertilization has a significant impact on the performance of various fungal and bacterial PSM inoculants in maize grown on neutral to alkaline soils with limited P availability. In greenhouse experiments, six strains of Pseudomonas, Bacillus, Paenibacillus, Streptomyces, and Penicillium with proven P-solubilizing potential, completely failed to promote P acquisition in maize grown on a calcareous Loess sub-soil pH 7.6 with nitrate fertilization… Show more

This study demonstrates that the form of nitrogen fertilization has a significant impact on the performance of various fungal and bacterial PSM inoculants in maize grown on neutral to alkaline soils with limited P availability. In greenhouse experiments, six strains of Pseudomonas, Bacillus, Paenibacillus, Streptomyces, and Penicillium with proven P-solubilizing potential, completely failed to promote P acquisition in maize grown on a calcareous Loess sub-soil pH 7.6 with nitrate fertilization and rock phosphate (Rock-P) as a sparingly soluble P source. However, after replacement of nitrate fertilization by ammonium, stabilized with the nitrification inhibitor 3,4-dimethylpyrazole-phosphate (DMPP), five out of seven investigated PSM inoculants (comprising 12 fungal and bacterial PSM strains) exerted beneficial effects on plant growth and reached up to 88% of the shoot biomass production of a control supplied with soluble triple-superphosphate (TSP). Stabilized ammonium combined with PSM-inoculants improved P acquisition (Trichoderma harzianum T22, Pseudomonas sp. DMSZ 13134), while other strains particularly stimulated root growth (T. harzianum OMG16, Bacillus amyloliquefaciens FZB42), which promoted the acquisition also of other mineral nutrients, such as N, K, and Mn. A similar effect was recorded under field conditions on an alkaline clay-loam soil pH 8.6. The combination of stabilized ammonium with a range of consortium products based on T. harzianum OMG16, B. amyloliquefaciens, micronutrients, and humic acids completely compensated the effect of a TSP fertilization on field establishment, nutrient acquisition, and yield formation in maize, while non-stabilized urea-di-ammonium phosphate fertilization was largely ineffective. These findings suggest that the efficiency of PSM-plant interactions can be influenced by the form of N fertilization, offering promising perspectives for synergistic effects with stabilized ammonium fertilizers. Show less

The use of plant growth-promoting microorganisms (PGPMs) as bio-effectors (BEs) to improve the nutrient acquisition of crops has a long history. However, limited reproducibility of the expected effects still remains a major challenge for practical applications. Based on the hypothesis that the expression of PGPM effects depends on soil type and the properties of the applied fertilizers, in this study, the performance of selected microbial inoculants was investigated for two contrasting… Show more

The use of plant growth-promoting microorganisms (PGPMs) as bio-effectors (BEs) to improve the nutrient acquisition of crops has a long history. However, limited reproducibility of the expected effects still remains a major challenge for practical applications. Based on the hypothesis that the expression of PGPM effects depends on soil type and the properties of the applied fertilizers, in this study, the performance of selected microbial inoculants was investigated for two contrasting low-fertility soils supplied with different organic and inorganic fertilizers. Greenhouse experiments were conducted with tomato on an alkaline sandy loam of pH 7.8 and an acidic loamy sand of pH 5.6 with limited phosphate (P) availability. Municipal waste compost, with and without poultry manure (PM), rock phosphate (RP), stabilized ammonium, and mineral nitrogen, phosphorus and potassium (NPK) fertilization were tested as fertilizer variants. Selected strains of Bacillus amyloliquefaciens (Priest et al. 1987) Borriss et al. 2011 (FZB42) and Trichoderma harzianum Rifai (OMG16) with proven plant growth-promoting potential were used as inoculants. On both soils, P was identified as a major limiting nutrient. Microbial inoculation selectively increased the P utilization in the PM-compost variants by 116% and 56% on the alkaline and acidic soil, while RP utilization was increased by 24%. This was associated with significantly increased shoot biomass production by 37–42%. Plant growth promotion coincided with a corresponding stimulation of root growth, suggesting improved spatial acquisition of soluble soil P fractions, associated also with improved acquisition of nitrogen (N), potassium (K), magnesium (Mg), and calcium (Ca). The results suggest that successful application of microbial biofertilizers requires more targeted application strategies, considering the soil properties and compatible fertilizer combinations. Show less