High Soil Nutrient Research Articles

Partial substitution of chemical fertilizer with organic fertilizer and slow-release fertilizer benefits soil microbial diversity and pineapple fruit yield in the tropics

The partial substitution of chemical fertilizers with organic fertilizer and slow-release fertilizer is an effective approach for improving crop yield and soil quality. However, few studies have paid close attention to pineapples in the tropics. Here, a 2-year field experiment was conducted to elucidate the differences in pineapple rhizosphere soil microorganisms, bulk soil chemical characteristics, and pineapple fruit yield under different fertilization treatments (CK: no fertilizer application; FP: conventional chemical fertilizer application; OPT: reduced chemical fertilizer application; OPTO: based on OPT, with organic fertilizer replacing 20 % of nitrogen (N); OPTS: based on OPTO, with slow-release fertilizer replacing 15 % of N), and the links between soil microorganisms and soil chemical properties and pineapple fruit yield were analyzed. Compared with FP, OPT, OPTO and OPTS treatments significantly increased bulk soil pH and organic matter (OM) content while reducing the amount of available phosphorus (AP), available potassium (AK), nitrate nitrogen (NO3−) and ammonium nitrogen (NH4+); in addition, they also highly increased the bacterial diversity index and pineapple yield (P < 0.05). It was found that Proteobacteria, Actinobacteria, Chloroflexi and Acidobacteria were the four major bacterial phyla (relative abundances >10 %) in all treatments, while Ascomycota was the main phylum of fungi. Specifically, the OPTS treatment increased the abundance of Chloroflexi, Acidobacteria and Basidiomycota but decreased the abundance of Proteobacteria, Actinobacteria and Ascomycota. Correlation analysis found that bulk soil pH, OM, AP, AK, NO3− and NH4+ levels were all important factors influencing the formation of the rhizosphere soil microbial community. Overall, the OPTS treatment resulted in relatively high soil nutrient content, microbial diversity and the number of beneficial microorganisms, which increased pineapple yield. Therefore, OPTS can be used as a high-yield and sustainable fertilization method for pineapple.

Responses of nitrogen and phosphorus resorption of understory plants to microscale soil nutrient hetero-geneity in Chinese fir plantation.

We compared the interspecific differences in leaf nutrient resorption of two dominant understory species (Lophatherum gracile and Oplimenus unulatifolius), and analyzed the correlations between the intraspecific efficiency of leaf nutrient resorption and nutrient properties of soil and leaves in Chinese fir plantation. The results showed high soil nutrient heterogeneity in Chinese fir plantation. Soil inorganic nitrogen content and available phosphorus content varied from 8.58 to 65.29 mg·kg-1 and from 2.43 to 15.20 mg·kg-1 in the Chinese fir plantation, respectively. The soil inorganic nitrogen content in O. undulatifolius community was 1.4 times higher than that in L. gra-cile community, but there was no significant difference in soil available phosphorus content between the two communities. Both leaf nitrogen and phosphorus resorption efficiency of O. unulatifolius was significantly lower than that of L. gracile under the three measurement bases of leaf dry weight, leaf area, and lignin content. Resorption efficiency in L. gracile community expressed on leaf dry weight was lower than that expressed on leaf area and lignin content, while resorption efficiency expressed on leaf area was the lowest in O. unulatifolius community. The intraspecific resorption efficiency was significantly correlated with leaf nutrient contents, but was less correlated with soil nutrient content, and only the nitrogen resorption efficiency of L. gracile had significant positive correlation with soil inorganic nitrogen content. The results indicated that there was significant difference in the leaf nutrient resorption efficiency between the two understory species. Soil nutrient heterogeneity exerted a weak effect on the intraspecific nutrient resorption, which might be attributed to high soil nutrient availability and potential disturbance from canopy litter in Chinese fir plantation.

Effect of Coffee Ages and Shade Types on Soil Moisture and Soil N, P, K Availability in UB Forest

Water and nutrients is important for plant which has its characteristics. This study has been carried out in the UB (Brawijaya University) forest about soil moisture content during rainy and dry seasons, Total-N, -P, -K from litter on different types of shade and age of coffee plants, and their effect on soil Available-N, -P, and -K. There are P1 (control), P2 (4-year-coffee + pine), P3 (7-year-coffee + pine), P4 (4-year-coffee + mahogany), and P5 (7-year-coffee + mahogany). These treatments affected to total soil moisture storage, Total-N, -P, -K of litter, and Available-N, -P, -K in the soil. The soil moisture storage change between rainy and dry seasons was 36.97 mm. The highest Total-N, -P, and -K of litter was 11.00 kg ha-1 y-1 at P3, 1.06 kg ha-1 y-1 at P2, and 4.35 kg ha-1 y-1 at P3, which was inconsistently associated with high soil nutrients. The highest Total-N was 0.40 (0-20 cm), 0.27 (20-40 cm), 0.30% (40-60 cm) at P4, Available-K was 1.69 (0-20 cm), 1.64 (20-40 cm), 1.87 cmol kg-1 (40-60 cm) at P5, and Available-P was 15.21 (0-20 cm), 14.06 (20-40 cm), 12.64 mg kg-1 (40-60 cm) at P1.

Effects of arbuscular mycorrhizal fungi on plant growth and herbivore infestation depend on availability of soil water and nutrients.

Fitness of plants is affected by their symbiotic interactions with arbuscular mycorrhizal fungi (AMF), and such effects are highly dependent on the environmental context. In the current study, we inoculated the nursery shrub species Artemisia ordosica with AMF species Funneliformis mosseae under contrasting levels of soil water and nutrients (diammonium phosphate fertilization), to assess their effects on plant growth, physiology and natural infestation by herbivores. Overall, plant biomass was synergistically enhanced by increasing soil water and soil nutrient levels. However, plant height was surprisingly repressed by AMF inoculation, but only under low water conditions. Similarly, plant biomass was also reduced by AMF but only under low water and nutrient conditions. Furthermore, AMF significantly reduced leaf phosphorus levels, that were strongly enhanced under high nutrient conditions, but had only minor effects on leaf chlorophyll and proline levels. Under low water and nutrient conditions, specific root length was enhanced, but average root diameter was decreased by AMF inoculation. The negative effects of AMF on plant growth at low water and nutrient levels may indicate that under these conditions AMF inoculation does not strongly contribute to nutrient and water acquisition. On the contrary, the AMF might have suppressed the direct pathway of water and nutrient absorption by the plant roots themselves despite low levels of mycorrhizal colonization. AMF inoculation reduced the abundance of the foliar herbivore Chrysolina aeruginosa on plants that had been grown on the low nutrient soil, but not on high nutrient soil. Fertilization enhanced the abundance of this herbivore but only in plants that had received the high water treatment. The lower abundance of the herbivore on AMF plants could be related to their decreased leaf P content. In conclusion, our results indicate that AMF negatively affect the growth of Artemisia ordosica but makes them less attractive to a dominant herbivore. Our study highlights that plant responses to AMF depend not only on the environmental context, but that the direction of the responses can differ for different components of plant performance (growth vs. defense).

Effect of Different Poultry Manure on the Performance of Tomatoes (Lycopersicon esculentum mill)

Purpose: Tomato is one of the most popular and versatile vegetables in the world and organic production with high yields of desirable quality are a target of many producers. However, the yield of tomatoes in Uganda are low compared to other parts of the world. The reason is that most soils in Uganda are low in fertility. There is widespread soil degradation, due to massive soil erosion resulting into loss of organic matter, high soil acidity and nutrient imbalance hence low crop yields. This study aimed at establishing the effect of different poultry manure on the performance of tomatoes.&#x0D; Methodology: The field trials were conducted in the mid altitude environment at BSU farm. Four treatments which included broiler, Layer, combination of Broiler and Layer chicken manure and the control were applied. The study was carried out in a randomized complete block design replicated four times. Measurements were made on number of leaves, number of flowers, plant height, fruit weight, fruit size, number of tomatoes and yield per hectare. Broiler and layer chicken manure increased the number of leaves, plant height number of flowers, number of fruits, fruit weight and fruit size significantly.&#x0D; Findings: The results indicate that poultry manure is very rich in macro nutrients. Among the treatments, broiler and layer chicken manure gave the highest fruit yield of 13.8 and 13.4 tons per hectare (t/ha) respectively. A combination of the manure produced 12.8 t/ha and the control treatment gave the lowest yield of 8.1 tons per hectare (t/ha). There was no significant difference between broiler and layer chicken manure. Both manures were equally good and enhanced yield. Therefore, farmers may opt for either of the two depending on the availability.&#x0D; Recommendation: The study recommend that either broiler or layer chicken manure can be used for production of tomato in order to achieve high yields.

Soil properties and root traits are important factors driving rhizosphere soil bacterial and fungal community variations in alpine Rhododendron nitidulum shrub ecosystems along an altitudinal gradient

Both soil properties and plant root traits are pivotal factors affecting microbial communities. However, there is still limited information about their importance in shaping rhizosphere soil microbial communities, particularly in less-studied alpine shrub ecosystems. To investigate the effects of altitude (3300, 3600, 3900, and 4200 m) on the diversity and composition of rhizosphere soil bacterial and fungal communities, as well as the factors shaping rhizosphere soil microbial communities, we conducted this study in alpine Rhododendron nitidulum shrub ecosystems from the Zheduo mountain of the eastern Tibetan Plateau. Results demonstrated that bacterial community diversity and richness decreased to the lowest value at 3600 m and then increased at higher altitudes compared with 3300 m; whereas fungal richness at 3300 m was much lower than at other altitudes, and was closely related to soil properties and root traits. The composition of rhizosphere soil bacterial and fungal communities at the low altitude (3300 m) was different from that at high altitudes. Permutational multivariate analysis of variance and redundancy analysis indicated that soil properties (soil water content, pH, NO3−-N, and available phosphorus) and root traits (surface area, and maximum depth) were the major factors explaining the variations of rhizosphere soil bacterial and fungal communities. Specific bacterial and fungal taxa along altitudes were identified. The bacterial taxa Planctomycetota was dominant at 3300 and 3600 m with low soil nutrient availability and high root surface area, whereas the fungal taxa Mortierellomycota was abundant at 3900 and 4200 m with high soil nutrient availability and low root surface area. These results suggested that different soil microbes can respond differently to altitude. This study provides a novel insight into factors driving rhizosphere soil bacterial and fungal community variations, which could improve our understanding of microbial ecology in alpine R. nitidulum shrub ecosystems along altitude.

The relationship between ecological factors and commercial quality of high-quality foxtail millet “Jingu 21”

The commercial quality of foxtail millet grain (Setaria italica L.) includes appearance quality, functional quality, and cooking and eating quality, which directly determine whether consumers will purchase the product. We studied the relationship between ecological factors and commercial quality attributes of foxtail millet “Jingu 21” from twelve production areas. The results showed that altitude, latitude, and diurnal temperature range were negatively correlated with b*, total flavones content (TFC), setback (SB), consistence (CS) and pasting temperature (PTM), but positively correlated with L/B and breakdown (BD). In contrast, average temperature, average precipitation, average humidity, available nitrogen, phosphorus, and potassium had positive effects on 1,000-grain weight (KGW), b*, TFC, CS, and PTM and had a negative impact on L/B and BD. Climate factors had a greater effect on the commercial quality of foxtail millet than soil factors, and the influence of climatic factors was particularly obvious in the early and middle growth periods. The multivariate equation between ecological factors and the comprehensive score of foxtail millet commercial quality is Y = 1,159.745–4.496X1 (altitude) + 19.529X5 (≥10℃ effective accumulated temperature) − 166.327X10 (organic matters). In conclusion, high temperature and precipitation are conducive to high quality appearance and the accumulation of functional substances, while a high diurnal temperature range and high soil nutrients are conducive to the formation of cooking and eating quality. The impact of ecological factors on foxtail millet quality is complicated and it is essential to select a cultivation site that is matched to the intended use of the foxtail millet being produced.

Positive feedbacks between savanna tree size and the nutritional characteristics of “Islands of fertility” are amplified by sociable weaver colonies

In arid environments, areas of high soil nutrient concentrations are common under woody plants due to ecosystem functions, including faunal deposition. Sociable weavers (Philetairus socius) are birds that build nests on camelthorn (Vachellia erioloba) and shepherd (Boscia albitrunca) trees and their faeces enrich the soil. Nevertheless, the soil under the nests is devoid of vegetation. We evaluated the hypotheses that the presence of trees and weaver nests alters soil properties, which vary with tree species and size as well as nest size, but that the area devoid of vegetation under nest trees is due to physiological drought, lack of viable seeds or nutrient toxicity. We sampled and analysed soil properties under trees with and without a sociable weaver nest and the grassland between them. Soils under trees were characterized by higher N (2.3-fold) and P (1.3-fold) compared to grassland areas. Furthermore, soils under nest-trees had higher N (3.5-fold), and P (4.1-fold) concentrations than soils under trees without nests. Some soil properties also varied with increasing tree and colony size. Soil water infiltration rate decreased under nest-trees with increased colony size, limiting seed germination, despite good seed banks and nutrient-rich soils. This combination of feedbacks establishes these trees as powerful ecosystem engineers.

Influence of Soil Nutrient Toxicity and Deficiency from Three Ecuadorian Climatic Regions on the Variation of Biological, Metabolic, and Nutritional Properties of Moringa oleifera Lam.

Moringa oleifera Lam. contains numerous essential constituents found in all plant parts (leaves, pods, and seeds). From all its edible parts, the leaf represents an effective remedy with high potential for medicinal applications. Ecuador is part of the new promising cultivation areas for Moringa, and therefore our study is emphasized to determine the influence of soil nutrition, toxicity (excess), and deficiency, from three main areas of this country, correlated with its climatic characteristics, on the mineral components, bioactive compounds' synthesis, and antioxidant capacity of Moringa. Different analyses were performed in soil and especially leaf samples for phytochemical content, antioxidant activity, calcium, protein, and vitamin C determination to identify the relationship between soil nutrients, abiotic conditions, and the therapeutic potential of this species cultivated in Ecuador. The obtained values using methods such as DPPH, FRAP, and ABTS showed a high antioxidant capacity of the leaves from the Coastal Ecuadorian region, related with total phenolic compounds' content (through the Folin-Ciocalteu method) and flavonoids in samples, with results obtained under the positive influence of high soil nutrients such as Ca, Mg, Mn, and Fe. We can conclude that M. oleifera from the coastal area of Ecuador presents the right environmental and soil conditions to positively influence its mineral and phytochemical content, making it suitable for incorporation into foods and medicines to solve the nutritional and medical problems in Ecuador and worldwide.

Wheat straw biochar amendment significantly reduces nutrient leaching and increases green pepper yield in a less fertile soil

Declining soil fertility and inefficient water and nutrient use pose a growing challenge to increasing agricultural production to meet growing global food demand. As a soil amendment, biochar can potentially serve in addressing these issues; however, its impacts on nutrient leaching from soils of different pre-existing fertility levels are poorly understood. A potted green pepper ( Capsicum annuum L. var. Red Night) production system, arranged in a randomized complete block design, imposed two soil fertility management approaches (‘fertile’: standard soil + [N:P:K (kg ha −1 ) 140:165:160] vs. ‘less fertile soil’: 1:1 standard soil : sand, [N:P:K (kg ha −1 ) 140:190:240], factorially combined with three levels of wheat straw biochar amendment [0%, 1%, and 3% (w/w)]. Biochar treatment effects on nutrient leaching ( NO 3 − -N and PO 4 3 − -P ) and plant yield were assessed for each soil fertility management approach. Across soil fertility types, biochar amendments ( vs. the lack thereof) significantly decreased ( p ≤ 0 . 05 ) leachate volume (68%–91%) and cumulative NO 3 − -N (78%–93%) and PO 4 3 − -P (80%–99%) losses, whereas NO 3 − -N , and PO 4 3 − -P concentrations in the leachate were only significantly reduced (p ≤ 0.05) under the 3% biochar amendment. Pepper marketable yield in the less fertile soil was significantly (40%, p ≤ 0 . 05 ) greater under the 3% biochar amendment than the non-amended treatment; however, no such difference existed in the fertile soil given its initially high soil nutrient levels. While farmers can amend soils with biochar to reduce nutrient leaching, its impact on plant productivity will depend on the rate of amendment. • Biochar significantly increased water use in fertile and less fertile soils. • Biochar amendment drives soil organic matter content than soil fertility status. • Soil nitrate-N loss was chemically driven in fertile and less fertile soils. • Biochar increased pepper yield in nutrient-deficient sandy soils. • Root length & surface area regulate pepper yield than root diameter & total volume.

Effects of flooding outweigh those of vegetation restoration on key processes of carbon and nitrogen cycling in a degraded riparian zone

Active revegetation (AR) and natural regeneration (NR) are two restoration approaches widely used to rehabilitate degraded riparian ecosystems, which are subjected to frequent hydrological fluctuations owing to climate change and human activities. Nevertheless, the impacts of restoration approaches and hydrological changes on the key processes of carbon and nitrogen cycling, particularly in degraded riparian ecosystems, remain unclear. In this study, we conducted hydrological experiments, which began in 2016, at three flooding zones (extreme flooding zone, severe flooding zone, and moderate flooding zone) of AR and NR areas in the Three Gorges Reservoir to investigate the effects of restoration approach and hydrological changes on soil properties, vegetation diversity, microbial characteristics, denitrification rates, and greenhouse gas fluxes. The results showed that compared with NR, AR did not change vegetation diversity, microbial diversity, and soil denitrification rates, but decreased soil ammonium and total carbon contents. The vegetation coverage of each flooding zone was more than 90%, and vegetation diversity was relatively high in the moderate flooding zone. Moreover, the maximum denitrification rates and CO2 fluxes were observed in the extreme flooding zone along with a high soil nutrient content. Additionally, the effect of flooding zone superseded the impacts of restoration approaches since AR could only significantly increase the CO2 flux (p < 0.05). Overall, this study elucidates the impacts of restoration approaches and hydrological changes on C and N cycling, and aids in developing restoration strategies for degraded riparian ecosystems.

Yield and quality properties of alfalfa (Medicago sativa L.) and their influencing factors in China

Alfalfa (Medicago sativa L.) is the most valuable perennial forage crop, and assessing its yield and quality properties is essential to evaluate forage value of livestock production. However, regional patterns and controlling factors of the yield and quality of alfalfa have not been well documented. In this study, using a dataset of 7166 observations from 301 sites across the country collected from 334 publications, we explored the relationships between the yield and quality properties of alfalfa in China and the effects of environmental factors and management practices on them. The average dry matter yield of alfalfa was 11.18 ± 6.69 Mg ha-1, with average crude protein, ether extract, crude fiber, acid detergent fiber, neutral detergent fiber, crude ash, nitrogen-free extract, calcium, phosphorus and relative feed values of 19.05 ± 2.87%, 2.62 ± 0.97%, 27.16 ± 5.21%, 31.29 ± 5.58%, 40.48 ± 6.34%, 9.49 ± 1.59%, 38.67 ± 7.49%, 1.68 ± 0.55%, 0.25 ± 0.12%, and 151 ± 31.94, respectively. Alfalfa quality decreased with increasing yield. Geographically, alfalfa had higher yield and crude protein content in South China than in other regions. Quality was positively correlated with both precipitation and temperature, while yield showed a positive relationship with temperature but no significant relationship with precipitation. High soil nutrient availability (e. g., soil available nitrogen, SAN; soil available phosphorus, SAP; soil available potassium, SAK) improved the yield, while high SAN and SAP contents increased the crude protein content. The alfalfa yield increased and the quality decreased with advancing maturity and age, whereas increasing the number of harvests may benefit the quality. This study documents comprehensive information on the yield and quality of alfalfa and provides insights for policy makers for the effective management and sustainable development of alfalfa production.

Identifying the difference in bacterial composition and life history strategies between high versus low nutrient soils

In this study, we aim to identify bacterial composition in soils treated with and without wood chips, as well as high levels and low levels of nitrogen. In order to do this, we used both culture dependent methods including plating, observing, and GenIII plates; as well as culture independent methods which include microbiome sequencing and EcoPlates. By doing this, we concluded that the bacterial communities differ between unamended and wood-chipped treated soils. Multiple differences were identified: rate of carbon consumption, bacterial diversity, rRNA gene copy number, and colony morphologies. Identifying the bacteria in wood-chipped soils will allow us to understand their effect on biogeochemical cycles, plant pathogens, and relationship with the trees (symbiotic/pathogen). Additionally, understanding the effect lower nitrogen levels have on the bacterial composition of soils can lead to reduction of synthetic fertilizer use, therefore lessening the environmental impact of nitrogen.

Nutrient status of integrated rice-crayfish system impacts the microbial nitrogen-transformation processes in paddy fields and rice yields.

Increasing rice yield is essential for alleviating global food crisis. High soil nutrient level guarantees high rice yields in conventional rice monoculture (RM) systems, but excessive unconsumed nutrients act as pollutants and can even threaten rice growth. The integrated rice-crayfish (IRC) system aims to transfer the excess nutrients from crayfish to paddy fields to improve the comprehensive utilization rate of nutrients and create additional profits, while the responding characteristics of IRC microbial communities in paddy fields and rice yields to the nutrient status remain unclear. Considering the crucial roles of microbiomes in promoting nutrient cycling for crop absorption in rice production progresses, the composition and functional characteristics of soil microbial communities from six IRC farms with variant nutrient statuses in the Yangtze River Delta were surveyed in this study. Compared with RM systems, IRC systems with appropriately improved (p < 0.05) soil quality created favorable nutrient (FN) status accompanied by 15% rice yields increase, while IRC systems with extremely high nutrients (HN) status (p < 0.01) accompanied by 14% rice yields reduction. Soil microbial diversity and network complexity were maintained in FN-IRC systems, but declined in HN-IRC systems, with the Shannon index significantly decreased by 9.2% and network density decreased from 0.135 (in RM) to 0.062. In the FN-IRC systems, the keystone taxa identified by co-occurrence networks displayed inextricably positive correlations with soil nitrification potential (calculated by normalization of amoA gene abundance) and rice yields. While in HN-IRC systems, the large loss of keystone taxa might limit soil nitrogen fixation potential (calculated by normalization of nifH gene abundance), and further rice yields. Our study indicates that soil nutrient management in IRC systems claim attention, and the improvement of nitrogen metabolism is the key to realize agricultural cleaner production.

Landscape management alters relationships between edaphic conditions, bacterial diversities, and nitrogen-cycling traits

Urbanization has dramatic effects on riparian ecosystem functioning. China implemented ecological restoration through the landscape construction of riverside green spaces. Soil microbiome restoration is key to the recovery of riverside ecosystem functioning. However, it remains unknown how restoration strategies affect biodiversity-function relationship. Here we examined bacterial communities and functional profiles using high-throughput sequencing, quantitative polymerase chain reaction in adjacent pairs of landscaped and undeveloped riparian green spaces. We also explored how soil properties, bacterial communities, and functions interact using structural equation modeling. Results showed that the landscaped system had higher soil nutrients and moisture, and more uniform bacterial alpha and beta diversity than the undeveloped system. Landscaped systems harbored more abundant denitrification genes, while undeveloped systems had more abundant nitrification genes. In the landscaped system, bacterial alpha diversity is independent of soil factors and negatively correlated with multiple nitrogen-cycling processes. In resource-limited undeveloped system, bacterial alpha diversity negatively responded to soil nutrients, but positively affected nitrification. Moreover, soil nutrients negatively and positively impacted denitrification and dissimilatory nitrate reduction to ammonium (DNRA), respectively in the undeveloped system. In the landscaped system, high soil moisture promoted denitrification and anammox (anaerobic ammonium oxidation), which contributed to nitrogen loss. Collectively, landscape management influenced bacterial diversity, function, and their relationship by altering soil resource.

Modelling and mapping soil nutrient depletion in humid highlands of East Africa using ensemble machine learning: A case study from Rwanda

Soil nutrient depletion is one of the major causes of high yield gaps and nutrient deficiencies in East Africa highlands, including Rwanda. This research sought to determine the current soil nutrient balance and its spatial variation in 10 Rwandan agro-ecological zones. Soil nitrogen (N), phosphorus (P) and potassium (K) depletion in croplands were calculated using data from 455 field trials of the Optimizing Fertilizer Recommendations in Africa (OFRA) project in Rwanda. Calculated soil nutrient balances (NPK) and 15 environmental covariates were used to calibrate soil nutrient depletion models using ensemble machine learning (EML) and 10-fold cross-validation. In the 2019–2020 growing season, annual N and K depletions were 33.6 kg N ha−1 yr−1 and 71.0 kg K ha−1 yr−1, with a positive P balance of 2.30 kg P ha−1 yr−1. High soil nutrient uptake and high soil nutrient loss due to erosion and leaching were two main causes of NPK depletion. Spatial variations of NPK balance were influenced by soil nutrient stocks, soil erosion, elevation, rainfall, soil texture, and soil bulk density. The 10-fold cross-validation showed that coefficients of determination (R2) of NPK models were 62%, 58%, and 58%, respectively. Compared to single models, ensemble machine learning improved NPK model accuracy up to 5%. Our research revealed that soil nutrient depletion was highest in the northwest and lowest in the southeast of the study area. We conclude that increasing soil nutrient inputs without reducing soil nutrient loss due to soil degradation will not decrease soil nutrient depletion in Rwanda and ensemble machine learning outperforms single models in predicting soil nutrient balance. Thesolutiontoreducehighsoilnutrientdepletionin all agro-ecological zones of Rwanda would be to prioritize soil and water conservation measures and increase soil nutrient inputs.

Guinea Grass Establishment in South Texas Is Driven by Disturbance History and Savanna Structure

Non-native grass invasion is a leading driver of biodiversity loss and degradation of rangeland ecosystem services. The reproductive mode and output of alien species mediate invasion, and their differential propagule pressure has implications for management outcomes. Propagule success, however, is context dependent. Resource availability promotes invasion and is heavily influenced by disturbance regimes. This study measured the reproductive phenology and establishment of Guinea grass's vegetative and seed-based reproduction in the field and the greenhouse. We asked how differences in vegetation type (woodland vs. grassland), disturbance history (brush management), and their interaction mediate the invasion process of Guinea grass. We documented differences in reproductive phenology as a function of vegetation type and disturbance history in the field. We measured seedling emergence and establishment in the greenhouse by fully crossing environmental variables with soils from two different disturbance levels. Finally, we estimated propagule pressure across vegetation types and disturbance history using data collected from the field and greenhouse trials.We found that areas associated with higher soil nutrients (under nitrogen-fixing mesquite trees and soil disturbance) had higher seed and stolon propagule pressure. Conversely, low disturbance and grassland areas had lower propagule pressure and were associated with lower nutrients. In the greenhouse, seedling establishment interacted with vegetation and disturbance. Seedlings growing in soils from mottes in a high-disturbance pasture had higher biomass and shoot length. However, the low disturbance pasture's specific root length was highest in mottes, indicating a higher allocation to roots, investing toward resource capture. Subsequently, we posit a hypothesis for Guinea grass spread in South Texas. Our findings suggest potential management steps, including treating Guinea grass under wooded cover to reduce overall propagule pressure and minimize soil disturbance during brush management of partially invaded woodlands.

Fertility Effects on Blueberry Gall Midge (Diptera: Cecidomyiidae) in Wild Blueberry (Vaccinium angustifolium; Ericales: Ericaceae).

Blueberry gall midge, Dasineura oxycoccana (Johnson) (Diptera: Cecidomyiidae) is a pest in American cranberry, Vaccinium macrocarpon Aiton (Ericales: Ericaceae) and wild blueberry, Vaccinium angustifolium Aiton (Ericales: Ericaceae), and has been observed in areas of high soil and foliar nutrient levels. New management strategies, including fertilization, will need to be altered to sustain wild blueberry production under climate change and, in turn, may impact the occurrence of this pest. The purpose of this study was to measure the effect of diammonium phosphate (DAP) fertilizer application on density of infested stems and the combined effects of fertilizer application with and without infestation on wild blueberry systems. This study was conducted at two field sites in Jonesboro and Washington, ME during 2020 and 2021. Despite increases in habitat availability (blueberry cover) for the gall midge and greater infestation density, wild blueberry production benefited from DAP application. This was shown in the number of buds per stem at both sites, as well as in stem height, flowers, green fruit, blue fruit per stem, and total yield at the Washington site. Foliar nitrogen and phosphorus levels had a significant positive linear relationship with infestation density. Growers applying fertilizers should monitor blueberry gall midge field infestation levels due to our findings that DAP fertilizer impacted infestation density and the interaction of DAP fertilizer with infestation impacted wild blueberry production.

Relating Invasibility and Invasiveness: Case Study of Impatiens parviflora

Data on alien species show that plant invasions are caused by a complex combination of characteristics of invasive species (invasiveness) and characteristics of invaded environment (invasibility).Impatiens parviflorais one of Europe’s top invasive species. The present study aimed to evaluate molecular diversity of populations of highly invasive in LithuaniaI. parvifloraby applying several DNA markers and relating genetic parameters to abiotic and biotic environment. For sampling, urban forests, riparian forests, and agrarian shrublands were selected. Three different DNA-based techniques, Simple Sequence Repeats (SSR), Inter Simple Sequence Repeat (ISSR) markers, and Random Amplified Polymorphic DNA (RAPD), were used for detecting genetic variation between 21 populations. All population individuals were monomorphic and homozygotic for four loci and heterozygotic for one locus by SSR analysis. Hierarchical analyses of molecular variance at ISSR and RAPD loci revealed significant differentiation of populations depending on geographic zones of the country. Bayesian Structure analyses of molecular data demonstrated existence of many genetic clusters and this finding is in support to multiple introduction of the species. The polymorphism extent at ISSR loci was positively correlated with the total coverage of herbaceous plant species. The coverage byI. parviflorawas negatively correlated with the total number of herbaceous species and light in the sites. Our results indicate that Lithuanian sites withI. parvifloramight be distinguished by high soil nutrient levels. According to the principal component analysis, the coverage byI. parviflorawas a more important variable of populations compared to molecular data or parameters of abiotic environment. In conclusion, complexity of invasibility and invasiveness factors determine the variability ofI. parviflorasites, including genetic traits, coverage of invasive species and conditions of environment that were significant and interrelated.

Effects of residue types and plastic mulch on earthworm aporrectodea trapezoides (Duges, 1828) within mesocosms at a salt-affected soil

ABSTRACT Earthworm colonization is an effective management practice to improve soil conditions. In a salt-affected reclamation soil, we conducted a mesocosm experiment to test the effects of organic residue application (no organic residues, clover residues or sheep manure) and plastic film (mulching or no mulching) on the survival, biomass and production of earthworms (Aporrectodea trapezoides (Duges, 1828)). Results showed that application of organic residues yielded a higher survival rate (37–100%) and biomass (0.43–0.98 g) of earthworms than the treatments without organic residue, regardless of plastic mulch. Moreover, the application of sheep manure significantly increased earthworm survival (58%) and biomass (160%) compared to the application of clover residues, which may be due to high soil available resources and nutrients in the soils with sheep manure. No significant differences (p = 0.26) in the survival rate (37–100% and 47–82%) or biomass of A. trapezoides were observed between the mulch and no-mulch treatments. This study indicated that animal manure out-performed clover residues in promoting the growth and survival of A. trapezoides in a reclaimed, salt-affected soil. Moreover, plastic film mulching improved soil moisture, but had no effect on the survival and biomass of A. trapezoides.