Fertilizer Management Strategies Research Articles

In-situ nitrogen fate in the vadose zone of different soil types and its implications for groundwater quality in the Huaihe River Basin, China

This paper focused on nitrate fate in the vadose zone (VZ) and its implications for groundwater vulnerability under different soil types in the agricultural area of Huaihe River Basin, China. Isotopic compositions of nitrate (δ15N and δ18O) along with NO3− and Cl− concentrations were determined in the VZ-shallow groundwater continuum beneath silty-loam and silty-clay-loam, which are distinctive in texture and organic carbon (OC). In the soil zone ( 1 m in depth), however, the concurrent enrichment of δ15N–NO3− and δ18O–NO3− indicated the occurrence of denitrification, which showed a dependence on subsoil properties. Specifically, during wheat and maize land uses, denitrification removed as much as 76 %–88 % of the total nitrate where the subsoil was dominated by stratified OC-rich silty-clay-loam. In contrast, only 0 %–28 % of the nitrate was degraded via denitrification where the subsoil was composed of uniform, OC-depleted silty-loam. Furthermore, inactive denitrification and higher permeability in the silty-loam VZ implied higher groundwater vulnerability. This observation was consistent with the fact that groundwater NO3−–N concentration beneath silty-loam (11.24 mg L−1) was over two times higher than that of the silty-clay-loam (5.32 mg L−1), where stricter fertilization management and conservation strategies should be applied to protect groundwater quality.

Grain Yields and Nitrogen Use Efficiencies in Different Types of Stay-Green Maize in Response to Nitrogen Fertilizer.

The stay-green leaf phenotype is typically associated with increased yields and improved stress resistance in maize breeding, due to higher nitrogen (N) nutrient levels that prolong greenness. The application of N fertilizer can regulate the N status of plants, and furthermore, impact the photosynthetic rates of leaves at the productive stage; however, N deficiencies and N excesses will reduce maize yields. Consequently, it is necessary to develop N fertilizer management strategies for different types of stay-green maize. For this study, the senescent cultivar Lianchuang 808 (LC808), moderate-stay-green cultivar Zhengdan 958 (ZD958), and over stay-green cultivar Denghai 685 (DH685) were selected as experimental models. Our results revealed that yields of ZD958 were slightly higher than DH685 and notably improved over than LC808. Compared with a non-stay-green cultivar LC808, ZD958 and DH685 still maintained higher chlorophyll contents and cell activities following the silking stage, while efficiently slowing the senescence rate. The supply of N fertilizer significantly prolonged leaf greenness and delayed senescence for ZD958 and DH685; however, the effect was not obvious for LC808. The stem remobilization efficiency of N was higher in the moderate-stay-green cultivar ZD958, in contrast to LC808, while the transfer of leaf N was lower than LC808, which guaranteed high leaf N levels, and that sufficient N was transferred to grains in ZD958. To obtain the highest yields, the optimal N fertilizer rates were 228.1 kg hm−2 for LC0808, 180 kg hm−2 for ZD958, and 203.8 kg hm−2 for DH685. In future, the selection of stay-green type crops might serve as an important agricultural strategy to reduce the quantity of N fertilizer and increase N efficiency.

Growth Rate and Nutrient Uptake of Basil in Small-scale Hydroponics

To identify practices that may simplify the use of small-scale hydroponic systems for indoor gardening, we compared two nutrient solution management treatments for basil (Ocimum basilicum) production. Experiments were conducted for 8 weeks to evaluate the effect of biweekly replacement of the nutrient solution (W) vs. biweekly fertilizer addition without nutrient solution replacement (W/O) on growth and nutrient uptake of basil ‘Genovese Compact’ grown in either a greenhouse or an indoor environment. Greenhouse day/night temperature was 29/24 ± 4 °C, relative humidity (RH) was 65 ± 4%, and daily light integral (DLI) was 26.1 mol·m‒2·d‒1. The indoor environment had a constant ambient temperature of 21 °C, RH of 65%, and DLI of 9 mol·m‒2·d‒1 provided by broadband white lamps. Four plants were grown in 7.6-L replicate hydroponic systems, with 178 mg·L‒1 N from a complete nutrient solution in two experimental runs. Shoot fresh and dry mass, leaf number, and leaf area showed an increasing quadratic trend over time when plants were grown in the greenhouse. In contrast, growth over time was linear for plants grown indoors. Within each environment, solution management treatment did not affect growth, indicating that the simpler W/O strategy was adequate under these conditions. Plants grown in the greenhouse required more frequent refill water applications compared with indoors, which resulted in three to four times more refill water applied. Because indoor-grown plants had a decreased growth rate, nutrient uptake rate, and volume of water applied compared with plants grown in the greenhouse, electrical conductivity (EC) for the W/O treatment increased over time. Final nutrient solution concentration was highest for indoor-grown plants under the W/O treatment, and final tissue nutrient concentration was higher for plants grown indoors compared with the greenhouse. Final nutrient uptake (dry mass × nutrient concentration) was higher for plants grown in the greenhouse rather than indoors. Considering that EC increased in the solution of indoor-grown plants under W/O, an appropriate strategy using this treatment would require reducing fertilizer input indoors. To refine simple and robust fertilizer management strategies for indoor gardeners, further research is needed to test variables such as different plant species, cultivars, and water qualities.

Variations in Soil Chemical Parameters of Long Term Sugarcane Growing Alfisols under Contrasting Cropping Conditions at Sevanagala, Sri Lanka

This study was conducted to determine the variability of soil pH, macronutrients and Na contents in long term sugarcanegrowing Alfisols at Sevanagala, South-East of Sri Lanka. The study site included the entire sugarcane-growing area covering its contrasting cropping systems namely, irrigated and rain-fed cultivation on low humic gley (LHG) and reddish brown earth (RBE) soils, and adjacent undisturbed soils. The mean pH of the two soil types was significantly different and ranged from 4.5 to 9.3. Except some soils under rain-fed cultivation with a pH less than 5.5 in RBE soil and a pH greater than 7.5 in LHG soils, pH in all other soils favoured sugarcane growth. Plant available P content of soils were not significantly different among cropping conditions due to its wide variation. In both cropping systems and soil types there were areas with very low to nondetectable P levels. Exchangeable K content was significantly different between LHG and RBE soils with the latter having a mean concentration of 257 mg/ kg that is favourable for sugarcane cultivation. Though, the mean values are higher than the optimum range, there were K deficient patches in the studied area. Soil exchangeable Ca, Mg and Na contents were low in the study area but were significantly higher in LHG soils than in RBE soils contributing to alkalinity in the former soils especially under rain-fed conditions. The sugarcane-growing soils except LHG under rain-fed conditions showed chemical properties similar to undisturbed soils in the area highlighting their buffered nature despite long-term sugarcane cultivation. This study also emphasised the need for site-specific soil fertility management strategies for the Sevanagala sugarcane growing areas.

Effect of long term fertilization management strategies on methane emissions and rice yield

Optimum fertilization is an efficient method to maintain rice yield and reduce N-losses. It is essential though to evaluate methane emissions from paddy fields, to further understand its impact on greenhouse gas budget. Therefore, a field experiment was conducted to investigate the effect of long-term optimum fertilization on CH4 emissions and rice yield. We collected data in the 7th and 8th year from a field experiment initiated in 2010. Four optimum fertilization strategies, reduced N-fertilizer and zero-P treatment (RNP, 200 kg N/ha), sulfur-coated urea combined with uncoated urea treatment (SCU, 200 kg N/ha), organic fertilizer combined chemical fertilizer treatment (OCN, 200 kg N/ha), organic fertilizer treatment (OF, 200 kg N/ha); and two controls, the farmers' N management (FN, 270 kg N/ha) and zero-N treatment (N0), were employed. The results showed the rice yields achieved for the optimum fertilization treatments (RNP, SCU, OCN, and OF) were similar with those for the FN. No significant differences in CH4 emissions among all treatments. Cumulative seasonal CH4 emissions were negatively correlated with grain yield (P < 0.05). In the RNP and SCU treatments, soil available K, mcrA gene and available P were the key variables affecting CH4 emissions; soil available K, available P and SOC contents were the key emissions factors for OCN and OF treatments. The SCU achieved the highest rice yield and lowest CH4 emission intensity among optimum fertilization treatments. These results suggest that long-term application of sulfur-coated urea combined with uncoated urea can maintain rice yield and reduce methane emissions from rice paddies.

Developing a Sustainable Management Strategy for Quantitative Estimation of Optimum Nitrogen Fertilizer Recommendation Rates for Maize in Northeast China

Excessive application of chemical fertilizers has caused a series of environmental problems, including environmental pollution. Quantitative estimation of a sustainable fertilizer recommendation rate is paramount for formulating fertilizer management strategies to improve productivity of low-yield regions and to prevent environmental damage. In this study, the database was drawn from 31 experimental sites in the main maize production region of Northeast China, during the period 2009 to 2013, to study the relationships between yield factors and nitrogen application rates, and to explore sustainable nitrogen (N) fertilizer recommendation rates based on analysis using the fertilizer response model. The fertilizer response model method is a technique that can provide effective performance predictions for the estimation of the optimum crop balanced fertilizer rates in varied agricultural regions. Results revealed that the average grain yield in treatment of N180 (the amount of nitrogen application rate was 90 kg ha −1) was highest, and the yield increase rate ranged from 4.77% to 58.53%, with an average of 25.89%. The sequence of grain yields in each treatment receiving N fertilizer management from high to low was: N180 &gt; N270 &gt; N90 in all the regions. The agronomic efficiency for applied N in N90, N180, N270 treatments was 11.8, 10.8, and 4.6 kg kg −1, respectively. The average optimum N fertilizer recommendation rate in Liaoning province was 180.4 kg ha −1, and the predicted optimum yield ranged between 7908.7 and 12,153.9 kg ha −1, with an average of 9699.1 kg ha −1. The mean optimum N fertilizer recommendation rate in western (WL), central and southern (SCL), eastern (EL), and northern (NL) of Liaoning province were 184.2, 177.2, 163.5, and 192.5 kg ha −1, and the average predicted optimum yields were 8785.3, 10,630.3, 9347, and 9942.4 kg ha −1. This study analyzed the spatial distribution of optimum fertilizer recommendation rates and the corresponding theoretical yield based on a large database, which helped to develop effective and environment-friendly N management strategies for sustainable production systems.

Critical Value of Soil Potassium for Potato Crops in Volcanic Soils

The critical value of soil exchangeable potassium (K) (mg K kg−1) is a valuable tool for an efficient K fertilization management in potato production systems. The aim of the present study was to determine the critical value of soil exchangeable K for potato crops grown in different environments and differing availabilities of initial exchangeable K. The data used in this study were taken from 34 experiments on K fertilization conducted in southern Chile from 1977 to 2017 by the National Potato Center at the Instituto de Investigaciones Agropecuarias (INIA). Yield responses to K fertilization rates were assessed with linear-plateau and Mitscherlich models in order to determine the critical soil exchangeable K across environments. Across experiments, the average fresh tuber yield ranged between 18 and 91 Mg ha−1. Fresh tuber yields decreased by up to 70% when no K fertilization was applied. Yield reduction was concentrated around 25% in response to K deficiency. Relative yields were described as significant by both linear-plateau and Mitscherlich models. However, relative yields were better described by the linear-plateau model (p < 0.01, R2 = 0.62; SEE = 0.11). The critical soil exchangeable K value identified with the linear-plateau model was 224 mg K kg−1. This critical K value will be useful for potato farmers that produce their crops in volcanic soils, such as Andisols. Moreover, this critical K value will help to increase K use efficiency through better K fertilization management strategies aimed at building and/or maintaining K levels in soils.

Thinning drives C:N:P stoichiometry and nutrient resorption in Larix principis-rupprechtii plantations in North China

Carbon (C):nitrogen (N):phosphorous (P) stoichiometry and nutrient resorption play an important role in terrestrial biogeochemical cycling and functioning. However, little information is available about the changes in C:N:P stoichiometry and nutrient resorption following thinning in plantation forests. Here, to reveal how thinning affects the C:N:P stoichiometry and nutrient resorption and their relationships, green leaves, senesced leaves and soil samples were collected from a pure Larix principis-rupprechtii plantation in North China after 9 years of four different thinning treatments, i.e., control (CK, 0% thinning), low thinning (LT, 14% thinning), moderate thinning (MT, 28% thinning) and high thinning (HT, 42% thinning). The results showed that excluding the green leaf C contents, thinning significantly increased the C, N, and P contents in green leaves, senesced leaves, and soil (p < 0.05). Thinning significantly decreased the C:N and C:P ratios in green leaves, C:P and N:P ratios in senesced leaves, and C:N, C:P, and N:P ratios in soil (p < 0.05), while thinning did not significantly affect green leaf N:P and senesced leaf C:N ratios (p > 0.05). The N resorption efficiency (NRE) showed no significant differences among different thinning treatments (p > 0.05), while thinning significantly decreased the P resorption efficiency (PRE, p < 0.05). There were different degrees of correlations between nutrient contents, stoichiometry ratios and nutrient resorption, and most of which were affected by soil properties (bulk density, soil water contents, available nitrogen and phosphorus, pH, electrical conductivity, soil microbial biomass C and N, and the activities of soil β-glucosidase, N-acetylglucosaminidase, and acid phosphatase). The N:P ratios of green leaves and senesced leaf litter and the nutrient resorption suggested that Larix principis-rupprechtii plantations in the study region were limited by N. Overall, the variations in nutrient contents, stoichiometry ratios, nutrient resorption, and soil properties demonstrate that thinning can significantly increase nutrient contents, promote nutrient cycling, and improve soil fertility. Among the four thinning treatments, in terms of nutrients, MT is recommended in Larix principis-rupprechtii plantations in North China. Furthermore, appropriate fertilization management strategies should be considered to improve N-limitation status.

Optimizing Soil Fertility Management Strategies to Enhance Banana Production in Volcanic Soils of the Northern Highlands, Tanzania

Banana is an important crop in high altitude areas of Tanzania, grown widely both as a food staple and as the main source of income. However, its production is constrained by low soil fertility, a result of gradual nutrient mining by the crop. Currently, soil fertility management in banana-based farming systems in the country relies mainly on applications of animal manure. However, the amount of manure produced in most farms is not enough to replenish soil fertility due to the small number of animals kept by smallholder resource-poor farmers who are the major producers in the country. Field experiments were conducted at three sites with varying soil types and contrasting weather conditions along the altitudinal gradients on the slopes of the volcanic mountains of Kilimanjaro and Meru, northern Tanzania to (1) investigate the effect of mineral nitrogen (mineral N) fertilizer applications on the growth and yield of Mchare banana (Musa spp., AA, a traditional East African highland cooking banana sub-group), at the four levels of 0, 77, 153, and 230 kg N ha−1 year−1 as a starter strategy to improve the current soil fertility management strategies, and (2) evaluate the effect of the combined use of inorganic and organic N sources on growth and banana fruit production as an alternative strategy to manage soil fertility and minimize animal manure requirements. The treatment factors were trial sites (Tarakea, Lyamungo, and Tengeru) as the main factor and N fertilization strategies (as urea alone, sole cattle manure, and in combination with urea, sole common bean (Phaseolus vulgaris L.) haulms as well as in combination with urea) as a sub factor. Bean haulms and cattle manure were applied each year for two years. Fertilization at 153 kg N ha−1 year−1 derived solely from urea significantly (p &lt; 0.001) resulted in high yield increment of up to 42% relative to the control. However, the increase was highest (52%) with the same N dose derived from cattle manure in combination with urea at 50% substitution. Sole bean haulms resulted in a smaller yield increment, the same as the lowest N dose from the sole urea fertilization treatment. The study concludes that soil fertility management in smallholder banana-based farming systems should not solely rely on animal manure and mineral fertilizers.

Combinations of a biofertilizer with micro-dosed chemical fertilizers increased yield of maize in a high acid saturated soil

Maize yields are usually lower for small-scale farmers relative to commercial farmers due to uncontrolled root diseases, acidic and nutrient deficient soils. Fertilizer micro-dosing is a promising strategy that has been earmarked to complement traditional fertilizer management strategies. However, this strategy is rarely known regarding its performance in maize systems in Southern Africa. The study was conducted over two seasons aiming at developing cost effective strategies on liming and fertilization to increase maize yields for farmers with low affordability and high acid saturated soils. Soil type used in this study had an acid saturation of 54% requiring 4.5 tons ha−1 dolomitic lime to obtain 4 tons ha−1 maize grain yields. Micro-dosing of NPK 2:3:2(34) fertilizer; superphosphate fertilizer and dolomitic lime were exploited to increase maize grain yields in a high acid saturated soil over time to cater for the farmer's affordability. A formulation of Bacillus megaterium was used as a biofertilizer. Micro-dosing of NPK 2:3:2(34) fertilizer increased maize yields by 64.6% (Season 1) and 13.6% (Season 2) when compared to the control treatment (unfertilized control) over the two seasons. Micro-dosing with superphosphate fertilizer alone significantly (P = 0.001) increased maize yield in Season 1 by 50.5% and Season 2 by 37.4% relative to the control. The combination of B. megaterium and micro-dosed NPK 2:3:2(34) fertilizer significantly (P = 0.001) increased maize yield in both seasons by 54.7% and 48.1%, respectively in comparison to the control. Whenever B. megaterium was included in the treatment combinations, there was a further increase in maize grain yield in both seasons. In all micro-dosing combinations where NPK 2:3:2(34) fertilizer and superphosphate were present, fertilizer use efficiency (FUE) were lower than micro-dosing of either NPK 2:3:2(34) fertilizer or superphosphate alone. The combination of precision placement of micro-dosed fertilizers and lime with B. megaterium may be a solution for small-scale farmers who have soils with high acid saturation.

Quantitative Estimation of the Nutrient Uptake Requirements of Peanut

Understanding the characteristics of the balanced nutrient requirements for peanut to achieve target yields is paramount when formulating fertilizer management strategies to increase yields and avoid fertilizer loss. Nutritional requirement estimation models can provide effective alternatives for the estimation of the optimum crop balanced nutrient requirements under varied agricultural conditions which are less time consuming and expensive. In the present study, the quantitative estimation of the optimum crop balanced nutrient requirements of peanut in China were obtained using quantitative evaluation of fertility of tropical soils (QUEFTS) model. The database covered the main agro-ecological region for peanut crops in China between 1993 and 2018. The predicted results of the QUEFTS model indicated that nutrient uptake requirements increased linearly with increasing pod yields until the yields had reached approximately 60% to 70% of the potential pod yields. It was found that with the increasing pod yields during the nutrient linear absorption stage, the plants had required 38.4 kg N, 4.3 kg P, and 14.0 kg K in total to produce 1000 kg of pods, and the corresponding internal efficiencies were 26.0 kg N/kg, 235.0 kg P/kg, and 71.6 kg K/kg, respectively. In addition, the balance rates of the removal nutrient in the pods were determined to be 29.4 kg N, 2.9 kg P, and 4.9 kg K per 1000 kg of pod yield, or approximately 76.5%, 67.4%, and 34.7% of N, P, and K in the total plants, respectively. This study’s field validation experiments verified the applicability and accuracy of the QUEFTS model. Therefore, it was considered to be an effective alternative for the estimation of the optimal balance N, P, and K uptake requirements for peanut crops. These findings will potentially be helpful when making future decisions regarding fertilizer recommendations for peanut crops in China.

Irrigation and Fertigation Management for Chilli (Capsicum annuum) under Drip Irrigation System

Water and nutrient are two key factors in improving production and quality of agricultural produce. Application of these two inputs through drip irrigation requires standardization of crop-specific water and fertilizer application levels in various agro-ecological regions. In order to develop better water and fertilizer management strategies in drip irrigated chilli, an experiment was conducted in split-plot design with 3 drip irrigation levels (I1 = 60 %, I2 = 80 %, I3 = 100 %) of full irrigation water requirement (IWR) in combination with 3 fertilizer levels (F1 = 80 %, F2 = 100 %, F3 = 120 %) of recommended dose of fertilizer (RDF). The treatment having water application at 80 % of IWR and 100 % of RDF (I2F2) showed significantly higher chilli yield (24.80 t.ha-1), water productivity (41.8 kg.ha-1. mm-1) and fertilizer use efficiency (55.1 kg.kg-1 of N). Results confirmed that excess use of water and fertilizer beyond threshold levels was not beneficial to plant growth and yield. The treatment I2 F2 showed highest net income (3,97,276 `. ha-1) and benefit-cost ratio (4.02), and is recommended for commercial cultivation of chilli in hot and humid regions as of Raipur, Chhattisgarh.

Irrigation and Fertigation Management for Chilli (Capsicum annuum) under Drip Irrigation System

Water and nutrient are two key factors in improving production and quality of agricultural produce. Application of these two inputs through drip irrigation requires standardization of crop-specific water and fertilizer application levels in various agro-ecological regions. In order to develop better water and fertilizer management strategies in drip irrigated chilli, an experiment was conducted in split-plot design with 3 drip irrigation levels (I1 = 60 %, I2 = 80 %, I3 = 100 %) of full irrigation water requirement (IWR) in combination with 3 fertilizer levels (F1 = 80 %, F2 = 100 %, F3 = 120 %) of recommended dose of fertilizer (RDF). The treatment having water application at 80 % of IWR and 100 % of RDF (I2F2) showed significantly higher chilli yield (24.80 t.ha-1), water productivity (41.8 kg.ha-1. mm-1) and fertilizer use efficiency (55.1 kg.kg-1 of N). Results confirmed that excess use of water and fertilizer beyond threshold levels was not beneficial to plant growth and yield. The treatment I2 F2 showed highest net income (3,97,276 `. ha-1) and benefit-cost ratio (4.02), and is recommended for commercial cultivation of chilli in hot and humid regions as of Raipur, Chhattisgarh.

Phosphate Solubilizing Bio-fertilizers and Their Role in Bio-available P Nutrient: An Overview

Soil is an ecosystem that plays a fundamental role in the availability of plant nutrients and contains a diverse array of beneficial microorganisms which can play a key role in soil fertility enhancement. Soil fertility management strategies for improving plant nutrients and crop productivity include the use of application of composts, vermicomposts and manures, and application of biofertilizer or microbial inoculants. The application of efficient phosphate-solubilizing microbial inoculants in agriculture opens up new insight for future crop productivity besides sustaining soil health. Development in the use of phosphate solublizing bio-inoculants are one of the recently promising options for meeting agricultural challenges imposed by the still growing demand for food. In this regard this review will show that phosphate-solubilizing microbes (PSMs) have tremendous potential as bio-fertilizers. Bio-fetilizer technologies can contribute to efficient utilization of limited resource of phosphorus fertilizers under low-input farming systems and guarantee the environment for livelihood. To strengthen the application of phosphate solublizing bio-inoculants, there is a need to know and understand the methods for their isolation and characterization of phosphate-solubilizing microorganisms and the mechanisms they used to solublize phosphate to make it available for plant nutrition. At the same time there is a need to understand various sources of bio-inoculants used for the primary isolation and characterization of indigenous phosphate solublizers which will be focused in this review. This review will also provide a broad spectrum for the various mechanisms of phosphate solublization and its impact in sustainable agriculture.

Pedological Characterization and Suitability Assessment for Cassava Production in Bukoba, Missenyi and Biharamulo Districts, Tanzania

A study was conducted in Bukoba, Missenyi and Biharamulo Districts, Tanzania with the objectives of characterizing, classifying and assessing the suitability of the study area for cassava production. A reconnaissance field survey using transect walks and auger observations was done in the study sites, which were geo-referenced in terms of international coordinates using Global Positioning System. Soil profiles representative of the study sites were excavated and named as MARU-P1, MISSE-P1 and BIHA-P1 for Bukoba, Missenyi and Biharamulo Districts, respectively. Soil profile description and data on the morphological features of the representative soils were collected according to the FAO Guidelines for Soil Description. Disturbed and undisturbed soil samples were collected from genetic soil horizons, processed and analyzed in a soil laboratory. Data on site characteristics, climate, soil morphological features and soil physical and chemical properties were used to classify the soils to the family level of the USDA Soil Taxonomy and to tier-2 of the FAO World Reference Base for Soil Resources. Soil suitability assessment of the experimental sites was done using a simple limitation method based on the FAO Framework for Land Evaluation. The results reveal that Pedons MARU-P1 and BIHA-P1 have similar morphological properties, which are different from pedon MISSE-P1. However, the studied pedons differ in their physical and chemical properties, implying differences in their use and management. The climate of the study sites is semi-humid with <i>Udic</i> soil moisture regime, which is generally favourable for crop production. According to the USDA Soil Taxonomy, pedons MARU-P1 and BIHA-P1 were classified as <i>“Typic Kandiudults”</i>. In addition, according to FAO World Reference Base for Soil Resources, pedons MARU-P1 and BIHA-P1 were classified as <i>“Haplic Ferralic Acrisols”</i> and <i>“Chromic Ferralic Acrisols”</i>, respectively. Pedon MISSE-P1 was classified as <i>“Typic Endoaquolls”</i> according to USDA Soil Taxonomy and as <i>“Fluvic Gleyic Phaeozems”</i> according to FAO World Reference Base for Soil Resources. Pedons MISSE-P1 and BIHA-P1 were both evaluated as marginally suitable while MARU-P1 pedon was evaluated as moderately suitable for cassava production due to soil fertility constraints. We recommended specific soil fertility management strategies in each studied site for optimum cassava yields.

Effects of fertilizer management strategies on maize yield and nitrogen use efficiencies under different densities

AbstractRational plant density and fertilizer management are important practices to improve maize (Zea mays L.) yield and nutrient use efficiency. Previous research indicated that plant density and fertilization had positive interaction on maize yield and N utilization. The research studied on the interactive effects of slow‐released fertilizer (added amino acid polymer biological preparation) and density on maize yield and nitrogen use efficiencies (NUEs). A 2‐yr field experiment with varieties Suyu29 (SY29) or Suyu30 (SY30) was conducted using a split‐split plot design. Three densities (6.0, 7.5, and 9.0 × 104 plants per ha) and three fertilization modes (0F‐no fertilizer, SF‐one‐time application of slow‐released fertilizer, and CF‐twice application of conventional fertilizer) were assigned. Results indicated that grain yields and NUEs of SF under 7.5 × 104 plants per ha were the highest both in SY29 and SY30. Compared with CF under 7.5 × 104 plants per ha, SF could improve pre‐ and post‐silking N uptake and promote N translocation from stalk and leaf into grain, which increased its contribution efficiency to grain N content and obtained higher NUE. The average N partial productivity, N agronomic efficiency, N recovery efficiency, and N absorption efficiency of SF were 5.3, 9.9, 20.1, and 11.4% higher than CF under 7.5 plants × 104 plants per ha. Increasing plant density, the grain yield, total N accumulation, and NUEs initially increased and then decreased both in SF and CF. These results suggest that one‐time application of SF combined with appropriate density could increase maize yield and NUE under our experiment condition.

Influence of Organic Enriched Manure and Inorganic Fertilizers on Plant Physiological Processes of Kenyan Tea Clone

Tea (Camellia sinensis L.) is one of the most popular beverages consumed in the world and Kenya is the leading exporter in Africa and only 3rd worldwide after China and India. Nutrient deficiency in soils and poor fertilization are possibly two reasons for low yields and quality of tea. The use of organic matter and mineral fertilizers has been proved to be a sound soil amendment and fertility management strategy. Therefore, this study was conducted to evaluate the possibility of using readily available organic manures in combination of inorganic fertilizers on the physiological processes of tea clones in Kenya. The study was conducted within Timbilil estate, KALRO- Tea Research Institute in Kericho County on variety clone TRFK31/8. It was laid out in a Randomized Complete Block Design (RCBD) and replicated three times. There were 14 treatments that randomly assigned in each block. Data on tea response was determined from photosynthesis rate, transpiration rate and stomatal conductance then recorded and analyzed using GenStat Version 15.1. There were significant differences between the treatments on the transpiration rate, stomatal conductance and the photosynthetic rate in both seasons for all the months recorded. The transpiration rate was highest during the wet season in the months of June, July and August while lower transpiration rates were recorded during the dry season in the months of December, January and February with 0.1 g m−2 s−1 transpiration rates recorded in several treatments in the month of February. Stomatal conductance, photosynthetic rate and transpiration rate were higher where NH4+ was introduced through the organic manure in all the seasons and therefore confirms that it is highly important to incorporate soil amendments with higher organic matter in tea production in Kenya.

How are annual CH4, N2O, and NO emissions from rice–wheat system affected by nitrogen fertilizer rate and type?

Although the effect of controlled-released fertilizer (CRF) on methane (CH4) and nitrous oxide (N2O) emissions has been investigated from many rice–wheat rotation systems, most studies were conducted either in the rice or in the wheat seasons. Few studies measured CH4, N2O, and nitric oxide (NO) emissions from rice–wheat rotation systems simultaneously. In this study, one-year outdoor pot experiments and two-year field experiments were conducted to investigate the effects of altering nitrogen (N) fertilizer type from traditional fertilizer (TF) (e.g., compound fertilizer and urea) to CRF and reducing 30% of the local conventional N application rate on CH4, N2O, and NO emissions from a typical Chinese rice–wheat rotation system. Results showed that the annual cumulative N2O emissions and EFN2O in the CRF treatment decreased by 3.91%–16.7% and 9.23%–20.7% compared with the TF treatment, respectively. These emissions also significantly decreased by 26.0%–34.4% and 18.1%–28.5% when local conventional N fertilizer application rate was decreased by 30% (P < .05). However, neither altering fertilizer type nor reducing 30% N fertilizer application rate affected CH4 emissions (P > .05), and the reduction effect of CRF on NO emissions could only be detected at the CRF fertilization rate at 270 kg N ha−1 per season but not at 190 kg N ha−1 per season. The annual total global warming potential in CRF treatment decreased by approximately 1.47%–9.17% compared with that in TF treatment. Moreover, this potential decreased by 8.29%–15.4% when 30% of the N application rate was reduced. Therefore, altering N fertilizer type from TF to CRF and applying optimal N rate should be encouraged as a partial substitution N fertilizer management strategy for the sustainable development of rice–wheat rotation systems.

Anaerobic oxidation of methane in paddy soil: Role of electron acceptors and fertilization in mitigating CH4 fluxes

The anaerobic oxidation of methane (AOM) in marine ecosystems is ubiquitous and largely coupled to sulfate reduction. In contrast, the role of AOM in terrestrial environments and the dominant electron acceptors driving terrestrial AOM needs deeper understanding. Submerged rice paddies with intensive CH4 production have a high potential for AOM, which can be important for greenhouse gas mitigation strategies. Here, we used 13CH4 to quantify the AOM rates in paddy soils under organic (Pig manure, Biochar) and mineral (NPK) fertilization. Alternative-to-oxygen electron acceptors for CH4 oxidation, including Fe3+, NO3−, SO42−, and humic acids, were examined and their potential for CH4 mitigation from rice paddies was assessed by 13CH4 oxidation to 13CO2 under anoxic conditions.During 84 days of anaerobic incubation, the cumulative AOM (13CH4-derived CO2) reached 0.15–1.3 μg C g-1 dry soil depending on fertilization. NO3- was the most effective electron acceptor, yielding an AOM rate of 0.80 ng C g-1 dry soil h-1 under Pig manure. The role of Fe3+ in AOM remained unclear, whereas SO42- inhibited AOM but strongly stimulated the production of unlabeled CO2, indicating intensive sulfate-induced decomposition of organic matter. Humic acids were the second most effective electron acceptor for AOM, but increased methanogenesis by 5–6 times in all fertilization treatments. We demonstrated for the first time that organic electron acceptors (humic acids) are among the key AOM drivers and are crucial in paddy soils. The most pronounced AOM in paddy soils occurred under Pig manure, followed by Control and NPK, while AOM was the lowest under Biochar. We estimate that nitrate (nitrite)-dependent AOM in paddy fields globally consumes ~3.9 Tg C–CH4 yr-1, thereby offsetting the global CH4 emissions by ~10–20%. Thus, from a broader agroecological perspective, the organic and mineral fertilizers control an important CH4 sink under anaerobic conditions in submerged ecosystems. Appropriate adjustments of soil fertilization management strategies would therefore help to decrease the net CH4 flux to the atmosphere and hence the global warming.

Agronomic effectiveness of urea deep placement technology for upland maize production

Effective fertilizer management is critical for sustainable maize production. Field trials were conducted in six locations in northern Ghana during the 2016 and 2017 farming seasons to evaluate the agronomic effectiveness and economic viability of urea deep placement technology (UDP), which involves deep placement of urea supergranules (USG), for maize production. This fertilization strategy was compared with four other maize fertilization strategies: (1) microdosing (MD); (2) farmer practice (FP), which involves surface broadcasting of granular fertilizer; (3) modified farmer practice (MFP), where granular fertilizer was incorporated into the soil; and (4) NPK-only, where no supplemental N was added. Averaged across all six locations and both years, UDP produced 18% more grain yield than MFP, 38% more than MD, 155% more than FP, and 270% more than NPK-only. The greatest apparent N recovery efficiency of 73% occurred in MD, followed by UDP (68%), NPK-only (63%), MFP (61%) and FP (35%), in that order. However, agronomic efficiency followed the order: UDP > MFP = MD > NPK-only = FP. The greatest gross profit margin of 49% was obtained with UDP, followed by MFP (41%) and MD (33%). Farmer practice resulted in a break-even level (3%) whereas NPK-only resulted in a loss (< − 35%). From the combined results, we conclude that, barring other external factors such as drought, flooding, pests, diseases, etc., UDP could be one of the most efficient fertilizer management strategies for sustainable maize production. Further studies should evaluate optimum timing of USG application for increased productivity and profitability.