Unfertilized Control Research Articles

Fertilization Induced Soil Microbial Shifts Show Minor Effects on Sapindus mukorossi Yield

Fertilization can improve soil nutrition and increase the yield of Sapindus mukorossi, but the response of soil microbial communities to fertilization treatments and their correlation with soil nutrition and Sapindus mukorossi yield are unclear. In order to investigate the characteristics of soil physicochemical qualities and the bacterial community, we carried out a field experiment comparing various quantities of nitrogen (N), phosphorus (P), and potassium (K) fertilizers to the unfertilized control treatments and the yield of Sapindus mukorossi in raw material forests in response to different applications of fertilizers and to try to clarify the interrelation among the three. Results showed that (1) there are significant differences in the effects of different fertilization treatments on the soil properties of Sapindus mukorossi raw material forests. The increase in the application rates of nitrogen or phosphorus fertilizers significantly reduced the soil pH value. (2) Compared with control, the α-diversity of bacterial communities was significantly lower in N3P2K2 and N1P1K2 treatments. Among the dominant groups of soil bacteria at the phylum level, the relative abundance of Chloroflexi showed an increase and then a decrease trend with the increase in N application. The relative abundance of Firmicutes, Bacteroidota, and Fusobacteriota was positively correlated with the application of P and K fertilizers, while the relative abundance of Acidobacteriota and Verrucomicrobiota decreased with the increase in P and K fertilizers. (3) The N2P2K2 treatment produced the highest sapindus yield (1464.58 kg/ha), which increased by 258.67% above the control. (4) Redundancy analysis (RDA) showed that the primary determinants of bacterial community structure were soil pH, total K, and effective P concentration. (5) Structural equation modeling (SEM) showed that soil nutrient content was the main direct factor driving the yield of Sapindus mukorossi, whereas the bacterial community attributes (e.g., diversity and structure) had minor effects on the yield. In summary, the rational use of formulated fertilization can change the bacterial community structure, improve the bacterial diversity, and increase the soil nutrient content, with the latter exerting a significant effect on the improvement of the yield of Sapindus mukorossi.

Root decomposition and nutrient dynamics in multifunctional forage‐biomass buffer‐strip systems

AbstractPerennial crops are thought as a solution for enhancing food security and providing ecosystem services under a changing climate, including forage‐biomass production, reduced erosion and nutrient leaching, and soil C accumulation. However, the drivers of root decomposition and C allocation in perennial multifunctional forage‐biomass buffer‐strips as affected by fertility management are poorly elucidated. Thus, study objectives were to assess root decomposition and soil CO2 efflux on switchgrass (Panicum virgatum L.), eastern gamagrass (Tripsacum dactyloides L.), silphium (Silphium integrifolium Michx.), and intermediate wheatgrass Kernza (Thinopyrum intermedium [Host] Barkworth & D.R. Dewey) treated with poultry litter (PL) relative to the unfertilized control. Root mass loss was greatest for silphium, owing to low neutral and acid detergent fibers and lignin contents (6%) relative to the other species (16%–25%). Root‐C loss was the greatest for intermediate wheatgrass (IW), mostly driven by hemicellulose degradation. Low root mass, surface area, and volume likely enhanced root decomposition for silphium and IW. Root mass loss and C, N, and P mineralization for novel perennial buffer‐strip species were greater in PL plots. Soil organic C stocks were mostly similar across forage‐biomass species × amendment combinations. Silphium‐PL had 27%–50% greater SOC stocks after 4 years, owing to higher root sloughing and C inputs to soil. Root decomposition rates were primarily affected by root chemical composition and morphology, while soil CO2 efflux was driven by soil moisture and temperature. Greater root sloughing, C inputs, and nutrient cycling showcase the potential for C storage and multiple purposes of novel perennial buffer‐strips.

A Spray Foliar Containing Methylobacterium symbioticum Did Not Increase Nitrogen Concentration in Leaves or Olive Yield Across Three Rainfed Olive Orchards

Biological nitrogen (N) fixation has been advocated in agricultural fields due to being considered a more sustainable way to introduce N into agrosystems than industrial N fertilizers. In this study, a foliar spray inoculant containing the microorganism Methylobacterium symbioticum was applied. This microorganism is known for fixing N in the phyllosphere, regardless of the cultivated species. This study was conducted in three rainfed olive orchards over three years. In two orchards managed according to European Union (EU) integrated production rules, the experiment was organized as a factorial design with inoculant (applied at two levels, yes and no) and N fertilization (applied to the soil at three levels, 0, 40, and 80 kg ha−1 of N). The third trial, managed according to EU organic farming rules, was organized in a completely randomized design with three treatments: with (yes) and without (no) inoculant and with a treatment involving a seaweed extract, also for foliar application. The microbiological inoculant did not consistently influence olive yield or N concentration in leaves across the three trials. Conversely, N application to the soil significantly influenced N concentration in leaves and olive yield. In one of the trials, in the third year of the study, soil N application (80 kg ha−1) resulted in an olive yield of ~eight times higher than the unfertilized control treatment. The seaweed extract also did not lead to significant differences in leaf mineral composition or olive yield compared with the other treatments. These findings from the on-farm research highlight the importance of accurately determining the conditions under which commercial products can deliver effective results. It is crucial to acknowledge that these products involve expenses not only in their acquisition but also in their application.

Evaluating shifts in species distribution following herbicide and fertilizer applications for smutgrass (Sporobolus indicus) control in bahiagrass

Abstract Novel management strategies for controlling smutgrass have potential to influence sward dynamics in bahiagrass forage systems. This experiment evaluated population shifts in bahiagrass forage following implementation of integrated herbicide and fertilizer management plans for controlling smutgrass. Herbicide treatments included indaziflam applied preemergence (PRE), hexazinone applied postemergence (POST), a combination of PRE + POST herbicides, and a nonsprayed control. Fertilizer treatments included nitrogen (N), nitrogen + potassium (N+K), and an unfertilized control. The POST reduced smutgrass coverage regardless of PRE or fertilizer application by the end of the first season and remained low for the three-year duration of the experiment (P < 0.01). All treatments, including nontreated controls, reduced smutgrass coverage during year 3 (P < 0.05), indicating that routine harvesting to remove the biomass reduced smutgrass coverage. Bahiagrass cover increased at the end of year 1 with POST (P < 0.01) but only the POST + fertilizer treatment maintained greater bahiagrass coverage than the nontreated control by the end of year 3 (P < 0.05). Expenses associated with the POST + fertilizer treatment totaled $348 ha-1 across the three-year experiment. Other smutgrass control options could include complete removal of biomass (hay production) and pasture renovation, which can cost threefold or greater more than POST + fertilizer treatment. Complete removal of biomass may reduce smutgrass coverage by removing mature seedheads, but at a much greater expense of $2,835 to $5,825 ha-1 depending on herbicide and fertilizer inputs. Bahiagrass renovation is $826 ha-1 in establishment costs alone. When pasture production expenses are included for two seasons post-renovation, the total increases to $1,120 ha-1 across three seasons. The importance of hexazinone and fertilizer as components of smutgrass control in bahiagrass forage was confirmed in this study. Future research should focus on the biology of smutgrass and the role of a PRE in a long-term, larger-scale forage system.

On-farm compost and parsley residues extract use on organic fennel crop to improve agronomic performance and environmental sustainability

ABSTRACT Recycling agricultural residues to obtain production factors directly in the farm could be crucial to improve sustainability. The aim of this study was to use plant residues to produce both organic amendments (on-farm compost) and plant biostimulants (liquid extracts). They were applied on a 2-year organic fennel crop, both alone (compost on-farm – OC) and combined (compost on-farm plus parsley extract – OCex) and compared with two commercial organic fertilizers (of vegetal origin – ORG-V; and of animal origin – ORG-A) and an unfertilized control, alone (NF) and combined with the extract (NFex). On average, the agronomic performance of compost treatments was higher than the unfertilized control and comparable to ORG-V. The use of the plant extract induced a synergistic effect with the on-farm compost, likely due to the P, K, Ca, Fe, and Mg supplementation by the extract to fennel crop. This is a relevant result, particularly in the perspective of widening the number of fertilizers produced inside the farm in organic farming, thus avoiding both synthetic fertilizers and commercial organic fertilizers. Finally, on-farm compost use reduced GWP emissions, since an average value of −12.44%, compared to the commercial fertilized treatments, was found, thus suggesting environmental sustainability.

Effects of nitrification and urease inhibitors on nitrous oxide emissions and concentrations driven by soil moisture in sandy soils

Soil moisture and nitrogen (N) fertilizer control the balance between nitrous oxide (N₂O) production and consumption in soil. However, the impact of nitrification and urease inhibitors on soil N₂O production and consumption under varying soil moisture levels remains insufficiently understood. In this study, a soil column experiment was conducted to investigate N₂O concentrations and accumulation at different soil depths (0, 5, 15, 30, and 60 cm) in sandy soil over two months. The soil was collected from a drip-irrigated field subjected to long-term cotton cultivation in an arid region. Four fertilizer treatments were applied: urea, urea + nitrification inhibitor (Dicyandiamide, DCD), urea + nitrification and urease inhibitors [N-(n-butyl) thiophosphoric triamide, NBPT], and an unfertilized control. These treatments were tested under three soil moisture levels [23%, 46%, and 70% water-filled pore space (WFPS)]. The results showed that treatments with inhibitors significantly reduced cumulative surface N₂O emissions by 33.2%–58.2% compared to urea alone. Notably, the treatment with both DCD and NBPT achieved the greatest reductions in surface emissions and in N₂O concentrations at 5 cm and 15 cm soil depths at 70% WFPS. Additionally, across all N fertilizer sources, 70% WFPS led to increased N₂O concentrations in the soil profile compared to lower soil moisture levels. Column N₂O accumulation was positively correlated with surface cumulative N₂O emissions under all three moisture conditions. Our study highlights that under high soil moisture conditions, DCD and NBPT can significantly mitigate intense N₂O emissions in sandy soils. This emission reduction is likely attributed to enhanced nitrification within the 0–15 cm soil layer rather than reduced N₂O diffusivity and denitrification along the soil profile. Therefore, we recommend applying nitrification and urease inhibitors under high soil moisture conditions as an effective strategy to reduce N₂O emissions in sandy soils.

Impact of No Tillage and Low Emission N Fertilization on Durum Wheat Sustainability, Profitability and Quality

Mitigation practices for cereal systems, including conservation agriculture and low emission fertilization, are required to face global challenges of food security and climate change. The combination of these climate-smart approaches was investigated for durum wheat in a dry region of the Mediterranean basin in two crop seasons. The experimental design consisted in two different genotypes, Marco Aurelio (high protein content) and Saragolla (higher adaptability), subjected to no tillage (NT) vs. conventional tillage (CT) and to two fertilization strategies (standard vs. low emission plus an unfertilized control). Different environmental and economic sustainability parameters as well as two different technological and nutritional quality traits were evaluated. Saragolla showed a better environmental adaptability and a higher nitrogen use efficiency, evaluated as partial nutrient balance (+27%), and was associated with a lower protein content (14.5% vs. 15.6%). NT was associated with an improvement in yield (+15%) and quality, i.e., micronutrients (Fe, Zn) and antioxidant capacity (+15%), in the drier crop year. Low emission fertilization did not reduce crop performance and its combination with NT showed a higher economic net return. The combination of the two mitigation practices improved not only environmental and economic sustainability but also the health quality of durum wheat under water limited conditions.

IMPACT OF INTEGRATED ORGANOMINERAL FERTILIZER APPLICATION ON GROWTH, YIELD, QUALITY, AND HEALTH-RELATED COMPOUNDS OF SWEET CORN

In this study, the effectiveness of two organomineral formulations (OMF I and OMF II) on the growth, yield, kernel quality and health-related compounds of sweet corn were evaluated. Organomineral fertilizers were compared with chemically fertilized and unfertilized control to evaluate their effects as a basic fertilizer source. Field experiments were conducted using a randomized complete block design, with three replications over 2 years. Two cultivars (cv. ‘Sentinel’ and cv. ‘Khan’) were used as plant material. The results indicated that (1) compared to control, the application of organomineral and chemical fertilizers resulted in improvements in most growth, yield and quality traits of sweet corn in both cultivars; (2) use of organomineral fertilizers led to similar or significantly higher than chemical fertilizer in plant height, leaf number per plant, ear size, ear weight, ear yield (husked and de-husked) and total soluble solids. However, these effects showed responses that varied with type of organomineral fertilizer or cultivar; (3) use of OMF I treatment with cv. ‘Khan’ significantly improved ear size, ear weight, ear yield (husked and de-husked), colour traits, total phenolic content and antioxidant activity compared to other treatments.

Integrated organic and mineral fertilizer strategies for achieving sustainable maize yield and soil quality in dry sub-humid inceptisols

Maize is one of the important cereal crops grown in rainfed regions of northwestern Himalayas, however, persistent use of chemical fertilizers coupled with poor soil nutrients and water holding capacity due to coarse textured soils poses serious threat to sustaining maize yield and soil health. To address these bottlenecks, a long-term experiment with application of organic manures and mineral fertilizer provides insights to quantify changes in soil organic carbon (SOC), crop yield and rain water use efficiency (RWUE) in rainfed area having low water use efficiency. A twelve years field experiment was conducted under dry sub-humid Inceptisols in northern India to study the potential impacts of organic and mineral fertilization on maize (Zea mays L.) productivity, water use efficiency and soil quality. Ten treatments were assessed, involving different nitrogen levels (20, 30, and 40 kg N ha⁻¹) combined with 10 tha⁻¹ year⁻¹ of farmyard manure (FYM), in-situ green manure from sunhemp, and the incorporation of Leucaena leucocephala leaves at 5 tha⁻¹ year⁻¹, including an unfertilized control. Maize yield increased linearly with increasing nitrogen application rates. The combination of FYM @ 10t ha−1 and 40 kg N ha−1(T4) yielded the highest maize production. Manure addition improved soil organic carbon (SOC) and major soil nutrients (N, P and K) while unfertilized control showed decline in soil nutrients compared to their initial values. Compared with control, incorporation of 10 t ha−1 FYM increased SOC by 1.3, 1.41, 1.44 times at application rate of 20, 30, 40 kg N ha−1, respectively. Application of N@40 kg ha−1 + 10t FYM ha−1 showed highest rain water use efficiency (RWUE) and relative production efficiency index (RPEI) (2.74 kg ha−1 mm−1 and 82, respectively) and the lowest rank sum of 6. Highly significant positive relationship existed between RPEI and RWUE, RPEI and sustainability yield index (SYI), RWUE and SYI indicated the superiority of FYM in combination with mineral fertilizer. Regression models, correlating yield with monthly rainfall and crop growing periods, indicated that the integration of FYM (10 tha⁻¹) with 40 kg N ha⁻¹ was most effective in achieving the highest relative soil quality index (RSQI) of 76 and the greatest sustainability yield index (SYI) of 49.3%. Based on results, we recommend balanced fertilization (N@40 kg ha−1 +10t FYM ha−1) which is easily manageable by farmers as the optimal strategy for improving soil quality and achieving sustainable maize productivity in nutrient depleted Inceptisols of northern India.

Phosphorus fertilization promotes carbon cycling and negatively affects microbial carbon use efficiency in agricultural soils: Laboratory incubation experiments

Soil organic carbon (SOC) loss from intensive agriculture represents a major global concern. Consequently, strategies to improve soil management to mitigate or abate SOC losses and enhance carbon (C) sequestration are urgently needed. Nutrient availability, especially nitrogen (N) and phosphorus (P), regulates soil C cycling and storage. While N effects are well studied, less is known about how soil P status and different fertilizer types affects SOC dynamics. This laboratory incubation assessed how two common P fertilizers, diammonium phosphate (DAP) and single superphosphate (SSP), affected microbial activity and C immobilization in the zone of soil directly around the fertilizer granule (prillosphere) across three contrasting agricultural soils (Inceptisol, Vertisol, Alfisol). Soils were amended with DAP or SSP granules and C turnover assessed with 14C-labeled glycine, malic acid or glucose, alongside unfertilized controls. After three weeks, soil pH, electrical conductivity (EC), Olsen-P and microbial C use efficiency (CUE) were measured. DAP increased pH in the Inceptisol (acidic soil), while SSP decreased pH in all soils. Both fertilizers increased EC and Olsen-P, but SSP enhanced Olsen-P more than DAP. Cumulative 14CO2 emissions were 19–20 % higher with P fertilizers compared to the control, with DAP stimulating faster initial C mineralization rates than SSP, except in the Alfisol. P addition reduced microbial CUE by 23–34 % across all soils and substrates versus the unfertilized control. We ascribe this reduction in CUE to an alleviation of nutrient limitation or a fertilizer-induced osmotic stress. The co-addition of N either in DAP or glycine did not alter the P-induced CUE response suggesting that P was more important than N in regulating microbial CUE in these soils. We conclude that P fertilization increased short-term C turnover and may lead to reduced C storage in soil, however, further long-term (>1 year) research is needed to identify optimum P management strategies to minimize C losses in agricultural soils.

Effect of Chinese Milk Vetch on Zinc Content and Zinc Absorption of Rice in Purple Tidal Mud Soil

Rice is a staple food crop that feeds billions globally. Addressing Zn deficiency in rice is crucial for improving nutrition and food security. Zn deficiency in rice is a widespread issue, especially in purple tidal mud substrates, which often exhibit low Zn availability. The objective of this two-year pot study was to explore the relationship between Zn content, yield components, and Zn absorption in rice grown in purple tidal mud substrate with varying amounts of Chinese milk vetch (Astragalus sinicus L.) incorporation. The experimental design consisted of seven treatments: an unfertilized control, a Chinese milk vetch control, a chemical fertilizer control, and four treatment variations incorporating Chinese milk vetch alongside chemical fertilizer applications. The results indicated that planting and applying Chinese milk vetch improved the grain yield of rice in purple tidal mud substrate, and the yield increased with higher levels of Chinese milk vetch applied. The increased grain yield resulted in higher Zn absorption in rice grains. The application of Chinese milk vetch, both solely and in combination with chemical fertilizers, had varying effects on zinc uptake and grain zinc formation efficiency in early and late rice, with the control and low-level Chinese milk vetch treatments generally exhibiting the highest performance across the two-year period. By introducing Chinese milkvetch following the use of chemical fertilizers, the Zn content in rice grains increased starting from the second year. The treatment with Chinese milkvetch applied at a rate of 2.25 t/hm2 showed the best results in increasing the Zn content in rice grains. The increase in Zn content and Zn uptake by the rice plants gave rise to a lowering of the DTPA-extractable Zn content in the purple tidal mud substrate. Sole Chinese milk vetch application and using Chinese milk vetch following chemical fertilizer application both increased Zn content extracted by DTPA in purple tidal mud substrate.

Nitrogen fertilization management and seeding density differently affect net blotch incidence and grain yield in one two-row and one six-row cultivar of barley

A two-year field experiment was carried out on barley (Hordeum vulgare L.) to test the effect of cultivar, N fertilization management and seeding density on crop growth, net blotch (NB) disease occurrence and yield. The three variables were factorially combined in a split-split-plot design as follows: 1) two barley cultivars, one two-row (H. v. distichum, cv Callas) and one six-row (H. v. hexastichum, cv Azzurro); 2) four N application schedules differing for rates and/or timing of N supply: unfertilized control; fertilized with 35 kg ha−1 of N at BBCH29 plus 30 kg ha−1 of N at BBCH31; fertilized with 70 kg ha−1 of N at BBCH29 plus 60 kg ha−1 of N at BBCH31; fertilized with 130 kg ha−1 of N simultaneously at BBCH31; 3) four seeding densities: 100, 200, 400 and 800 viable seeds m2. The three variables affected crop growth and NB occurrence resulting in different grain yield and quality. Results varied with the seasonal trend, in particular with rainfall regime and air temperature, for their possible effect on soil N dynamics and the presence of NB, which resulted in different source capacity, and for their effect on grain setting and filling, i.e., the sink capacity. Both N fertilization and seeding density increased NB pressure, with seeding density affecting the disease even under unfavourable weather conditions for NB development. At the maximum N fertilization rate, delaying N application helped limit plant height and the related risk of lodging, as well as NB symptoms, resulting in greater hectolitre weight and protein content together with no appreciable decrease of grain yield, provided seeding density was close to optimal (i.e., 400 seeds m−2) or higher.

Nutrient Allocation and Growth Responses of Senegalia polyphylla under Varied Fertilizer Regimes for Effective Forest Recovery.

To restore invaded areas, planting fast-growing native species such as Senegalia polyphylla (DC.) Britton & Rose (Fabaceae) is widely used. However, invasive grasses reduce light availability, alter fire regimes, and compete for water and nutrients, hindering the growth of native trees. Fertilization practices influence the competition dynamics between natives and invasives by altering soil fertility. Therefore, this study investigated the effects of mineral and organic fertilization on the nutritional status and growth of S. polyphylla cultivated during the first 120 days after transplanting. The experiment was conducted in a completely randomized design comprising five treatments and four replications, along with the unfertilized control (0-0%) as an additional treatment. Dystrophic red latosol and different proportions of mineral and organic fertilizers were used. The variables evaluated included dry mass of aboveground parts and roots, nutrient content in leaves, and nutrient use efficiency. The results showed that fertilizations with high nutrient concentrations (100-0% and 75-25%) resulted in greater accumulation of N, P, and K in the leaves, while balanced fertilization (50-50% and 25-75%) led to greater root dry mass. These results emphasize the importance of strategically choosing fertilizer formulations to promote the healthy development of seedlings in areas subject to interference from invasive grasses.

Reduced Effect of Commercial Leonardite and Seaweed Extract on Lettuce Growth under Mineral, Organic, and No Fertilization Regimes

In this study, two commercial products based on the main groups of contemporary biostimulants—a commercial leonardite and a seaweed extract—were tested with the objective of assessing the conditions under which they can enhance lettuce (Lactuca sativa L.) performance, particularly to determine if synergies with conventional fertilization methods can be observed. The experimental protocol was arranged as a factorial design with two factors: organic or mineral fertilization × plant biostimulant. The organic or mineral fertilization factor included five levels: two rates of a nitrogen (N) fertilizer (40 (Nmin40) and 80 (Nmin80) kg ha−1 of N), the same N rates applied as an organic amendment (Norg40 and Norg80), and an unfertilized control (N0). The plant biostimulants used were a commercial leonardite (leonardite) for soil application before planting, a commercial seaweed extract (algae) for foliar application during the growing season, and a control without plant biostimulant. Leonardite significantly increased lettuce dry matter yield (DMY) compared to the control only in the first growing cycle (11.5 and 13.5 g plant−1) and showed no significant interaction with conventional fertilization. It also consistently increased phosphorus (P) levels in the plant tissues. The seaweed extract did not show any effect on the plant, nor did it have any interactions with conventional fertilization regarding DMY. In contrast, with mineral fertilization, lettuce DMY increased from 8.0 and 4.0 g plant−1 (N0) to 22.2 and 12.0 g plant−1 (Nmin80) in the first and second growing cycles, respectively. The response to organic fertilization was lower, yet DMY still increased from 4.0 to 8.1 g plant−1 in the second growing cycle. Generally, this type of plant biostimulant is tested under some form of environmental stress, where it often yields positive results. In this study, the optimal cultivation conditions maintained for the lettuce in the pots likely explain the limited response to the biostimulants. This study suggests that the product labels should more clearly indicate whether they are recommended for general cultivation conditions or specifically for situations where a particular environmental stress can be anticipated.

The Crop Phosphorus Uptake, Use Efficiency, and Budget under Long-Term Manure and Fertilizer Application in a Rice–Wheat Planting System

Little is known about the effect of the long-term application of organic and inorganic fertilizers on P-use efficiency, P budget, and the residual effect of P fertilizer. To clarify the effect of different fertilization on soil P balance in a rice (Oryza sativa L.)–wheat (Triticum aestivum L.) rotation system is helpful to promote the sustainable development of agriculture. Thus, a thirty-five-year fertilizer experiment was conducted with eight treatments, including an unfertilized control (CK); chemical nitrogen (N), phosphorus (P), and potassium (K) fertilizers; and organic manure (M) either alone or in combination treatments (N, NP, NPK, M, MN, MNP, and MNPK). The results indicated that crop yields and P uptake were higher in the combined application of manure and chemical fertilizer treatments than in the manure or chemical fertilizer alone treatments. Soil P budget indicated a 23.4–55.4 kg P ha−1 yr−1 surplus in the organic combined with or without mineral fertilizer treatments, but the soil P budget indicated a 20.0 and 21.9 kg P ha−1 yr−1 deficit in the control and N treatments. The proportion of residual fertilizer P converted to soil available P in NP, NPK, M, MN, MNP, and MNPK treatments was 4.5%, 4.8%, 19.1%, 19.0%, 11.5%, and 13.3%, respectively, over a 35-year period. Furthermore, according to the higher P content and crop uptake in organic manure treatment compared with chemical P fertilizer alone, an organic addition could effectively reduce the use of chemical fertilizer and become an effective way of sustainable development in practice. Therefore, the combined application of organic and inorganic fertilizer will be a practical method to increase crop yields and soil P status in a rice–wheat planting system.

Soybean responds infrequently to phosphorus fertilization in Manitoba

Soybean ( Glycine max (L.) Merr.) production in Manitoba has increased substantially over the last 20 years, raising questions about phosphorus (P) fertilization in this region. Between 2013 and 2015, a study was conducted across 28 sites in Manitoba to evaluate the effect of P fertilizer rate and placement on soybean plant stand and seed yield. Treatments were 22.5, 45, and 90 kg P2O5 ha−1 applied as monoammonium phosphate, seed-placed, side-banded or broadcast, plus an unfertilized control treatment. Plant stand reduction due to seed-placed fertilizer toxicity was observed at five of 28 site-years, typically at the rate of 90 kg P2O5 ha−1. Stand reduction was most frequent on medium- to coarse-textured soils, dry soils or when seeding equipment had low seedbed utilization. Seed yield was reduced at two site-years due to seed placing 90 kg P2O5 ha−1, which reduced plant stands below the recommended threshold of 247 000 plants ha−1. Phosphorus fertilization did not increase seed yield, regardless of P rate, P placement, or Olsen soil test P level, except for one site-year where 45 and 90 kg P2O5 ha−1 increased seed yield by 343 and 430 kg ha−1, respectively. The extremely infrequent response to P fertilizer in combination with the high rate of P removal indicates that soybeans can use soil P reservoirs that are less available to other crops. Nevertheless, soybean growers in Manitoba should consider strategies for applying supplemental P to soybean or other crops in their rotation to maintain P fertility in soil.

DETERMINATION OF THE OPTIMAL FERTILIZATION RATE BY A NEW BIOORGANIC FERTILIZER TO ENHANCE THE GROWTH PARAMETERS AND NUTRITIONAL QUALITY OF RED BEETROOT (BETA VULGARIS L. SSP. VULGARIS)

The goal of this study was to investigate the effect of different rates of a new bioorganic fertilizer and an inorganic fertilizer on the parameters growth and the nutritional quality of red beetroot. A field trial was conducted using the randomized complete block design with six treatments and six replications: (T1= inorganic fertilizer, NPK 20-45-25 ha−1, T2= Bio-Organic Fertilizer “BOF” at 10%, T3= BOF at 20%, T4= BOF at 30%, T5= BOF at 60% and T6= unfertilized control). The total carbohydrate, protein and nitrate content of harvested red beetroot was measured analytically. Quantification of betanin was determined spectrophotometrically, while the antioxidant activity assessed free radical scavenging activities against DPPH. Statistical analysis of soils treated with 20 and 30% BOF showed similar results for the total weight of red beetroot and the weight and diameter of their bulbs. However, these treatments significantly (p < 0.05) increased the betanin content of red beetroot by 16 % compared to the conventionally grown samples. However, the investigation of the effect of the different rates of BOF on the IC50 value showed a decrease of up to 52% in favor of the T5 treatment compared to the inorganic fertilizer. In contrast, organically and conventionally growing red beetroot had similar average nitrate levels. In light of the crucial role of BOF rates, high levels of macro and micronutrients in the soil negatively affect all quality parameters of red beetroot.

Soil chemical responses to fertilization, with or without a cover crop, in an olive orchard in southwestern Buenos Aires (Argentina)

Our objective was to study the effect of fertilization on soil chemical traits on an olive orchard (artificially irrigated), considering areas with or without a cover crop, in southwestern Buenos Aires, Argentina, during the period 2020/2021. Fertilization treatments were (1) organic manure applied to the soil near the tree trunk; inorganic fertilization applied to the (2) soil or (3) to the leaves of Olea europaea L. trees; and (4) unfertilized control. Seeding of Vicia benghalensis L. and Avena sativa L. around subplots (one per each of the four studied treatments) constituted the areas with a cover crop. Subplots which were not seeded corresponded to the control areas. Soil pH was lower (p<0.05) under organic and inorganic soil fertilization. In areas without a cover crop in April 2021, soil nitrate concentrations were greater (p<0.05) under organic soil fertilization than in the control. At 0-20 cm soil depth, P concentrations were greater (p<0.05) under organic and inorganic soil fertilizations than in the other treatments. The greatest (p<0.05) K concentrations were found in the organic fertilization treatment. Organic soil fertilization on areas without a cover crop showed greater values for the soil chemical studied traits.

Enhancing crop productivity and its economic farm profitabilty of smallholder farmer through the use of green manures from Alnus acuminata

Decline in soil fertility is a major threat to land productivity and food security in the East African highlands. This calls for the application of nutrient inputs to improve crop productivity. A study was conducted in Nyabihu District of Rwanda from 2013 to 2016 to assess the effect of Alnus acuminata green manure (AGM)─applied in situ, through biomass alone, or combined with inorganic fertilizer─on the productivity and profitability of maize (Zea mays), beans (Phaseolus vulgaris), and potato (Solanum tuberosum). The treatments included application of AGM, inorganic fertilizer, combination of AGM and inorganic fertilizer, and unfertilized plot as a control (except for potato). These treatments were compared in two seasons and on two local soil fertility levels (medium and high) as defined by the farmer’s knowledge and experience. There was a convergence between farmers’ criteria and soil analysis in the soil fertility evaluation. Crops yields were analyzed using a linear mixed model while for other parameters, descriptive statistics were applied. The combination of AGM and inorganic fertilizer recorded the highest increment in maize (44%) and bean (46%) yields compared with inorganic fertilizer while it increased up to 87% compared with the unfertilized control. The financial analysis showed that AGM + inorganic fertilizer recorded the highest value-to-cost ratio (VCR) of 24.6 for potato and a significantly lower VCR (2.9) for maize and beans. The high VCR highlights a significant potential contribution of AGM + inorganic fertilizer to increase incomes of resource-constrained potato farmers in the Rwandan highlands. However, low crop prices possibly make this practice less attractive for those cultivating maize and beans.

Phosphorus Availability and Balance with Long-Term Sewage Sludge and Nitrogen Fertilization in Chernozem Soil under Maize Monoculture.

A continuous long-term field experiment with maize monoculture was conducted to evaluate the P availability and balance, DM yield, P uptake, and P sorption parameters in chernozem soil after 27 years. A total of 2 doses of nitrogen (120 and 240 kg ha-1) were applied as mineral nitrogen (N120 and N240) and sewage sludge (SS120 and SS240) and compared with unfertilized control (Con). The aboveground biomass (DM) yields significantly increased in the order of Con < SS120 < SS240 < N120 < N240 treatments and the maximum P uptake was recorded for both N240 and SS240 (25.1 kg P ha-1) according to the nutrient application gradient. The N120 and N240 treatments positively influenced the DM yield but negatively influenced the P balance (-648 and -678 kg P ha-1 27 years-1), gradually bringing a risk of P deficiency in the soil. On the other hand, applications of SS120 and SS240 positively influenced the P availability and pseudototal (PAR) content in the soil, which resulted in a buildup of legacy P or an increase in P saturation greater than the environmental threshold value. Aluminum was found to be a major controlling sorption factor for P in our chernozem soil.