Inorganic Phosphorus Fertilizers Research Articles

Pelletized Organomineral vs. Inorganic Nitrogen and Phosphorus Fertilizers: Impact on Wheat Nutritional Status, Productivity, and Grain Quality

Pelletized Organomineral vs. Inorganic Nitrogen and Phosphorus Fertilizers: Impact on Wheat Nutritional Status, Productivity, and Grain Quality

The global fate of inorganic phosphorus fertilizers added to terrestrial ecosystems

The global fate of inorganic phosphorus fertilizers added to terrestrial ecosystems

Effects of Inorganic Phosphorus and Organic Fertilizer on Growth and Yield of Common Bean (Phaseolus Vulgaris L.) under Kabul Conditions

In Afghanistan, the main reasons for low crop yields are low soil fertility. Growing human populations has resulted in shrinking land areas and decreased soil fertility. Also, the overuse of chemical fertilizers is considered to be the main cause of soil characteristics deterioration, such as soil fertility, soil biology, and soil physical properties. On the other hand, no research has been done to find the ideal phosphorus and organic (ORGOFERT) fertilizer rate for improving common bean production in Afghanistan. Thus, it is pertinent to determine the optimum phosphorus and organic fertilizer dose for common bean cultivation in Afghanistan, where this crop is grown expensively. In 2020, a field trial took place at the agriculture faculty research farm of Kabul University during the growing season. The trial utilized a randomized complete block design (RCBD) with three replications. Each plot measured 200cm x 300cm, with plants spaced 40 cm apart in rows and 20 cm apart within rows. Different amounts of phosphorus and organic fertilizer were applied in the experiment. The results indicated that employing 50 kg of ORGOFERT and 80 kg of P2O5 fertilizers per hectare led to enhanced growth parameters such as plant height, number of branches per plant, and number of green leaves per plant, as well as improved yield attributes including the number of pods per plant, number of grains per pod, 100-grain weight, and total grain yield per hectare. The ideal amount of phosphorous and ORGOFERT fertilizer to improve the growth and production of common beans under field conditions might be the rate of 80kg P2O5 + 50 kg ORGOFERT fertilizer ha-1 under Kabul's agro-ecological conditions.

Controlling Phosphorus Transport in Poyang Lake Basin under the Constraints of Climate Change and Crop Yield Increase

Phosphorus, as a key nutrient, plays an essential role in both algal growth in surface waters and crop development on land. Its presence in inorganic fertilizers is crucial for maximizing crop yields. However, an excessive accumulation of phosphorus in soils can lead to its loss and exacerbate eutrophication in water bodies. This study highlights the complex interplay among phosphorus management, agricultural productivity, and environmental health, particularly in the context of climate change’s influence on sediment transport and water pollution. We focus on the Poyang Lake Basin (PLB) and use a sophisticated process-based phosphorus model to forecast phosphorus load trends from 2020 to 2049. Our predictions indicate a significant increase in the total phosphorus load of the PLB due to the impact of climate change. To address these challenges, we explore a novel strategy combining organic and inorganic phosphorus fertilizers. This approach aims to improve crop yields while reducing non-point source phosphorus pollution through adjusted anthropogenic inputs. Our findings reveal that a synergistic application of these fertilizers, coupled with a controlled use of inorganic phosphate, can reduce its usage by more than 2.5% annually. This method not only contributes to a 2.2% average annual increase in livestock and poultry production but also promotes a 0.6% yearly growth in grain output. Consequently, it effectively diminishes non-point source phosphorus pollution, offering a sustainable solution to the dual challenge of enhancing agricultural productivity and protecting environmental health.

Effect of Mixed Manure and Inorganic Fertilizer on Phosphorus Adsorption and Desorption Characteristics of Vertisols in Haramaya District, Eastern Ethiopia

Applying inorganic phosphorus fertilizer is less effective in increasing crop yields in tropical soils due to precipitation and adsorption reactions. However, research suggests that partial substitution of organic and inorganic fertilizers has shown to improve the efficiency of applied phosphorus fertilizer by reducing its adsorption and enhancing desorption due to their synergistic effects. This study aimed to investigate the impact of treating the soil with mixed manure (MM) rates and blended nitrogen, phosphorus, sulfur, and boron (NPSB) fertilizer on the soil’s phosphorus adsorption and desorption characteristics. Results showed increased adsorbed phosphorus in all treatments, with increased added phosphorus (P) concentration from 100 to 500 mg kg−1. However, the efficiency of adsorbed P decreased significantly as added P concentration rates increased from 100 to 400 mg·kg−1 in all treatments and then decreased as the added P concentration advanced to 500 mg·kg−1. Moreover, in all treatments that received combined applications of MM and blended NPSB, both quantity and percentage of desorbed P showed a significant increase. The Freundlich adsorption coefficient and constant were also significantly reduced because of the combined application of MM and blended NPSB, compared to the control and their sole applications. Overall, the soil treated with a combined application of 15 t·ha−1 of MM with 100 kg·ha−1 of blended NPSB showed the highest reduction in the efficiency of adsorbed P, percentage of desorbed P, Freundlich adsorption capacity, and intensity by 8%, 37.5%, 60%, and 58%, respectively, as compared to the control. These findings indicate that the combined application of MM and blended NPSB can improve the P availability and uptake by maize by reducing its adsorption while increasing desorption characteristics. Finally, this experiment recommends further research on the long‐term effects of MM and blended NPSB on P adsorption and desorption characteristics of vertisols.

Biochar amendments to tropical paddy soil increase rice yields and decrease N2O emissions by modifying the genes involved in nitrogen cycling

Water management strategies are critical in regulating nitrous oxide (N2O) emissions from paddy soils under rice cultivation. Biochar is widely used as an amendment to decrease soil N2O emissions. However, the impacts of biochar amendment on N2O emissions under different water management strategies in paddy soils have not been investigated thoroughly, and the underlying mechanisms remain poorly understood. In particular, the effects of mid-season water drainage, a strategy used for water conservation, need to be better understood. In this study, a pot experiment was conducted including six treatments: alternating dry-wet conditions during the mid-season period without and with 2% (w/w) biochar (AWD1 and AWD2, respectively), continuous flooding during the mid-season period without (CF1) and with 2% (CF2) biochar, and regular mid-season drainage during the mid-season period without (CON1) and with 2% (CON2) biochar. All treatments received inorganic nitrogen, phosphorus and potassium fertilizers (NPK) administered in a split application. We found that fluxes of N2O emission peaked after the two fertilizers’ additions. No significant difference in the first N2O flux peak was found among different treatments. There also was no difference in the second N2O flux peak in both CF treatments, whereas biochar addition significantly decreased the second N2O flux peak in AWD2 and CON2 treatments. This was mainly due to increased nosZ gene copies and decreased ratios of denitrification and amoA genes to nosZ gene copies. Biochar amendments resulted in significant stimulation of nifH gene copies in the AWD2 treatment. Lastly, biochar increased rice yields in all treatments. Our study suggested that AWD2 was the optimal management strategy for mitigating N2O emissions and improving rice production in this tropical paddy soil.

Effects of long-term organic and inorganic fertilization on greenhouse gas emissions and soil nutrient stoichiometry in a rice–rice–fallow cropping system

Long-term use of organic and inorganic fertilizers can have a negative impact on greenhouse gas (GHG) emissions and nutrient stoichiometry in paddy soil. However, production of sufficient crops to meet food and feed demands globally requires the use of fertilizer in crop production. In the present study, we assessed the environmental impacts of five fertilizer treatments in a rice–rice–fallow cropping system: no fertilizer (CK); inorganic nitrogen, phosphorus, and potassium fertilizers (NPK); manure (M); inorganic phosphorus and potassium fertilizers with manure (PKM); and inorganic nitrogen, phosphorus, and potassium fertilizers with manure (NPKM). Soil parameters were analyzed to examine the relationships between GHG emissions, net ecosystem carbon budgets (NECBs), and soil nutrient stoichiometric ratios. Both the PKM and NPKM treatments increased grain yield and the soil carbon–nitrogen (C:N), carbon–phosphorus (C:P), and nitrogen–phosphorus (N:P) ratios compared to the CK treatment; they also decreased the nitrogen–potassium (N:K) ratio. In the combined fertilization treatments, the fallow season accounted for 9–13% of annual methane (CH4) emissions, whereas early rice accounted for 55–62 % and late rice contributed 38–45 %. Compared to the CK, PKM and NPKM fertilization increased the annual nitrous oxide (N2O) emissions by 52–73 % and 103–115 %, respectively, in both the rice and fallow seasons. In early rice, the C:P ratio and GHG intensity (GHGI) were negatively correlated with CH4 and N2O emissions, whereas both yield and CH4 emissions had strong positive associations with global warming potential (GWP). In the late rice season, GHGI was negatively correlated with carbon dioxide (CO2) and CH4 emissions, and N2O had strong positive associations with GWP. CO2 and N2O emission levels were greater from late rice than from early rice, although CH4 emissions from early rice contributed more to the annual GWP, resulting in higher carbon equivalent emissions but a lower carbon efficiency ratio in early rice output. A Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) optimization analysis suggested that PKM was the best fertilization method to improve yield while minimizing negative environmental impacts, followed in descending order by the NPKM, NPK, and M treatments.

Findings on agricultural cleaner production in the three Gorges Reservoir Area

The ‘rural revitalization strategy’ is important to achieve sustainable development in the Three Gorges Reservoir Area (TGRA), the largest reservoir in China, located in the poverty alleviation region of the Qinling-Daba mountains, and characterized as mountainous and hilly dominated by backwards resettlements. Pig farming around the reservoir area is a key industry, accounting for 0.90% of the arable land area in the country, while the annual pig market represents a 1.37% share of the national figure. Here, 12 study sites were investigated on-site for understanding agricultural green development in the TGRA. We found two main prevailing models: one of ecological circulation (EC), based on animal husbandry and recycling. Of the 12 site, six cases of the ecological circulation model relied on pig husbandry, combined with cropping (grains/fruits/vegetables) by eco-industrial chains, such as pig-biogas-fruit (grain/vegetables), to prevent environmental pollution, while promoting agricultural economic growth by recycling fecal residues and wastewater (FSW) from pig-husbandry facilities to the fields. Our analysis predicted that a farm holding 10,000 pigs may save inorganic nitrogen and phosphorus fertilizers by as much as 74.36 and 11.15 ton·a−1, respectively. On the other hand, five cases of ecological models oriented towards agritourism provided tourists with high-quality ecological products while coordinating environment protection with economic development. In addition, 11 research points applied water and fertilizer integration system for the purpose of saving water. However, lack of sufficient supporting arable land made intensive pig farming a risk of ecological degradation. Green control technologies are rarely used leading to an increase in the type and amount of pesticides. Our study has theoretical and practical significance for decision-makers to promote agricultural cleaner production (ACP).

Optimization of chemical fertilizer application for blueberry vegetative growth, fruit quality and soil condition

Commercial cultivation of blueberry has rapidly expanded in China in recent years. However, suboptimal fertilization results in poor growth and management practices in blueberry orchards. The present study studied fertilization of southern highbush blueberry in southwest of China. We evaluated the effects of inorganic nitrogen, phosphorus, and potassium fertilizers at different doses. Plant vegetative growth, leaf photosynthesis parameters, fruit quality and soil nutrient contents were analyzed. Application of ammonium sulfate enhanced fruit weight, sweetness, and nutrient content, including vitamin C and anthocyanin contents. Comparison of P and K fertilizer treatments revealed that 30 g P/plant in combination with 30 g K/plant conferred superior plant growth and improved fruit sweetness and nutrient content. Using ammonium sulfate as the N source and monopotassium phosphate as the P and K source contributed to maintenance of soil acidity

The Effect of Inorganic Nitrogen and Phosphorus Fertilizers, Chicken Manure and Their Combinations on Growth and Development of Common Bean (Phaseolus vulgaris L.)

The Effect of Inorganic Nitrogen and Phosphorus Fertilizers, Chicken Manure and Their Combinations on Growth and Development of Common Bean (Phaseolus vulgaris L.)

Impact of NPK Enriched Bio-Compost on Rice Yield and Sustainability of Nutrients in Sandy Loam Soils of India

ABSTRACT To feed the burgeoning population, the cultivation of rice is exploited on low fertility soils, which are otherwise not fit for its cultivation. To enhance the fertility status of such soils, the nutrient-enriched bio-compost play vital role in maintaining the soil productivity and yield sustainability. Field experiments were conducted on sandy loam soil for two years (2016–2017 and 2017–2018) to evaluate the impact of different combinations of N (nitrogen)-, P (phosphorus)-, and K (potassium)-enriched bio-compost with inorganic nitrogen, phosphorus and potassium fertilizers (NPK) on crop productivity, nutrient uptake, and soil fertility by rice under rice-wheat system. The results reported that growth parameters, yield attributing characters, grain and straw yield of rice improved significantly by different NPK-enriched bio-compost treatments. Rice grain yield increased significantly, that is, 4350 kg ha−1 with the application of 150% NPK over recommended fertilizer (3360 kg ha−1). Also, plant growth parameters and yield attributing characters improved with application of bio-compost applied @ 4 t ha−1. The NPK content in grains and their buildup in soil were significantly higher in treatments where 25% NPK were substituted through NPK-enriched bio-compost and 75% NPK through inorganic fertilizers. Overall, it is concluded that integrated use of 25% nutrients through NPK-enriched bio-compost and 75% nutrients through NPK inorganic fertilizers is the best option for the maintenance of soil health and sustainable rice yield.

Response of Coffee Husk Biochar on Growth of Faba Bean on Nitisol and Soil Nutrients

Soil fertility depletion and the associated soil acidity has become a serious problem to crop production in most highlands of Ethiopia. Fortunately, such problems can be reclaimed by the application of biochar as soil amendments which can be sequestered in the soil for several years. A pot experiment was conducted to investigate the effects of biochar on growth response and nutrient uptake of faba bean and soil nutrients. The design employed was a randomized complete block with four replications. Collected Composite soil from (0-20 cm) depths at different distance in the zigzag pattern and prepared, analyzed before conducting the pot experiment and after harvesting following the standard laboratory procedures. Prepared biochar samples were collected from Jimma University collage of agricultural and veterinary medicine. The parameters analyzed includes: Trace Metals using DTPA extraction, macronutrient using 1 N ammonium acetate (pH =7) extraction. Dry ashing method was used to determine nutrient uptake of plant samples. The treatments included control, recommended inorganic phosphorus fertilizer (RPF), 10 t h -1 coffee husk biochar (CHB) + RPF ,20 t h - CHB+ RPF,10 t h -1 CHB+50% RPF,20 t h - CHB+50% RPF, lime+ RPF, lime+50% RPF,50% lime+RPF+10 t h -1 CHB and 50% lime+50% RPF+10 t h -1 CHB. The studied soil and plant data were collected and subjected to analysis of variance and treatment means were compared at the 0.05 probability level using list significant difference test. The results revealed that application of biochar significantly improved growth of faba bean and soil nutrient content. The highest values for soil chemical parameters such as total nitrogen, available phosphorus and exchangeable cations were obtained from the application of 20 t/ha CHB. Likewise, the highest growth performance of faba bean including plant height, leaf number, chlorophyll content, nodulation number, root and shoot biomass, uptake of N, P and K were recorded from biochar-amended soil. Keywords: Amelioration, coffee husk biochar, faba bean, Nitisols DOI: 10.7176/JNSR/13-13-04 Publication date: July 31 st 2022

Straw residue incorporation and potassium fertilization enhances soil aggregate stability by altering soil content of iron oxide and organic carbon in a rice–rape cropping system

AbstractBoth iron (Fe) oxide and soil organic carbon (SOC) content, among other factors, drive the development and subsequent stability of soil aggregates. However, the mechanism of these drivers in paddy‐upland rotation systems with straw residue incorporation is not well understood. In this multiyear (2011–2017) trial, we sought to study the factors which drive the stability of soil aggregates in such a rice‐rape (RR) agronomic system. In order to examine the effect of straw residue incorporation and potassium fertilization on soil aggregation dynamics, we divided our trial into four treatments: inorganic phosphorus (P) and nitrogen (N) fertilizer; inorganic NPK fertilizer; inorganic NP fertilizer plus straw residue; and inorganic NPK fertilizer plus straw residue. Treatments which incorporated straw residue significantly increased both the geometric mean diameter (GMD) and the mean weight diameter (MWD) of soil aggregates. Soil aggregate stability was greater after rape harvest than after rice harvest, while SOC shows the opposite trend. Straw residue incorporation increased the SOC and, specifically, concentrations of aliphatic‐C and aromatic‐C, particularly in aggregates greater than 0.25 mm. Straw residue addition significantly increased both the amorphous (Feo) and complex iron oxide (Fep) contents of soil. In both bulk soil and in aggregates greater than 5 mm, SOC and Fep were positively correlated with MWD, while in aggregates less than 5 mm, Feo was positively correlated with MWD. Overall, we suggest that the increased concentrations of SOC, alkane‐C, Feo, and Fep in soils after incorporation of straw residue were responsible for increasing soil aggregate stability.

Pigeon Manure Tea Improves Phosphorus Availability and Wheat Growth through Decreasing P Adsorption in a Calcareous Sandy Soil

ABSTRACT There are many environmental problems related to the production of inorganic phosphorus (P) fertilizers as well as their continuous usage, which pose great challenges to sustainable agriculture. Applying inorganic P fertilizers combined with pigeon manure tea (PMT) could be a promising strategy to enhance P use efficiency and yield of crop plants. Therefore, this study investigates the effect of integrated use of inorganic P and PMT on P sorption using Freundlich sorption isotherms as well as the availability of P and its use efficiency by wheat grown in a calcareous sandy soil. Application of PMT amendment significantly enhanced P availability compared to the unamended soil. The PMT significantly decreased the rate of P sorption from 246 to 179 mL g−1 and sorption capacity of the soil from 388 to 298 µg P g−1 soil. Consequently, the P fertilizer quantity required to produce the desired level of P in solution (0.2 mg L−1) was low in PMT amended soil (114 mg P kg−1) than that in control soil (140 mg P kg−1). Application of inorganic P in combination with PMT increased P use efficiency (PUE) of the wheat plant. Thus, the combined application of PMT and P fertilizer has positive, complementary, and synergistic effects on P availability in soil and its uptake by wheat plants. Due to its low cost and easy availability, integrated use of PMT1:100 (2.4 t PM ha−1) and inorganic P fertilizer could be an effective amendment to reduce P-sorption and improve soil P availability in the calcareous sandy soil.

Coupling phosphate-solubilizing bacteria (PSB) with inorganic phosphorus fertilizer improves mungbean (Vigna radiata) phosphorus acquisition, nitrogen fixation, and yield in alkaline-calcareous soil

To overcome the problems associated with soil phosphorus (P) insolubility, soil inoculation with phosphate-solubilizing bacteria (PSB) can be used. In a field experiment, we evaluated the efficacy of PSB in enhancing mungbean P acquisition, nitrogen (N) fixation, and morphological and yield traits in alkaline-calcareous soil when added together with P as single superphosphate (SSP) or rock phosphate (RP) at 45 or 90 kg P2O5 ha−1. Coupling PSB with mineral P fertilizers (SSP & RP) improved P use efficiency, mungbean P acquisition, N2 fixation, nodulation, NP uptake, and the morphological and yield-related traits of mungbeans compared with non-fertilized controls and plots received P from mineral sources alone. Soil PSB inoculation with mineral P also improved post-harvest soil fertility relative to pre-harvest by improving soil organic matter from 0.61% to 0.70%, lowering pH from 7.74 to 7.68, and improving soil total N from 0.04 to 0.09%, ABDTPA-extractable P from 2.07 to 3.44 mg kg−1, and potassium (K) concentrations from 100.27 to 129.45 mg kg−1. When combined with PSB, RP generally performed better than SSP. Moreover, there was a significant correlation between soil N and plant N, while the correlation between soil P and plant P was non-significant. The correlation between soil organic matter content and NP uptake by mungbeans was also non-significant. Therefore, adding P as RP at 45–90 kg ha−1, together with PSB inoculation, can be recommended for improving mungbean P acquisition, use efficiency, optimum N2 fixation, and yield in alkaline-calcareous soils.

Effects of conservation tillage, phosphorus and variety on selected soil physical properties and cowpea productivity at Minna in Nigeria’s Southern Guinea Savanna

This study was conducted to evaluate the influence of conservation tillage, inorganic phosphorus fertilizer and variety on soil physical properties and cowpea productivity at Minna in the Southern Guinea Savanna of Nigeria. Three tillage practices (zero, reduced and ridged), three phosphorus rates (0, 30 and 60 kg P2O5 ha-1) and three cowpea varieties (IT93K-452-1, IT99K-573-1-1 and IT90K277-2) were factorially combined and laid out in randomized complete block design with three replications. Two crops of cowpea were cultivated sequentially. Soil and crop indices used for the evaluation were soil bulk density, soil organic carbon content, mean weight diameter, soil moisture content, haulm yield and grain yield. Conservation tillage significantly affected the four soil indices while phosphorus rates significantly affected soil organic carbon content, mean weight diameter and soil moisture content. There was varietal effect on soil organic carbon content and soil moisture content. Conservation tillage methods influenced haulm yield significantly but had no significant effect on grain yield. Phosphorus application and variety, on the other hand, significantly affected both haulm and grain yields. Notably, in the early harvest, application of 60 kg P2O5 ha-1 raised haulm yield from 2,489 kg ha-1 (untreated control) to 5,482 kg ha-1 , and grain yield from 614 kg ha-1 (untreated control) to 1,440 kg ha-1 , representing 120% and 135% increments for haulm and grain yields respectively. Farmers are advised to combine either zero or reduced tillage with 60 kg P2O5 ha-1 and IT99K573-1-1 for maximum haulm and grain yields.

Effects of complementary and sole applications of inorganic fertilizers and winery solid waste compost on maize yield and soil health indices

The development of plant nutrition systems that enhance soil productivity through the use of mineral fertilizers combined with organic fertilizers has recently gained increased attention. Two field experiments were conducted in 2018 (from February to June) and 2018/19 (from December 2018 to April 2019) to assess the effects of complementary application of inorganic nitrogen (N) and phosphorus (P) fertilizers (INPF) and winery solid waste (WSW) composts on maize yield and soil health indicators. The INPF and optimum rates of microbially inoculated and uninoculated WSW compost types were combined at different ratios (0:0, 75:25, 50:50, 25:75 and 0:100 w/w) to supply proportionate N and P amount. The recommended INPF rates for maize (200 kg N ha-1 and 90 kg P ha-1) were mixed and included as a standard control. The interaction of compost type and application rate had no significant effects on total biomass yield (TBY), grain yield (GY) and harvest index (HI). The compost type had significant effects on GY and HI in 2018/19. The TBYs obtained from the 50:50, 75:25 and 100:0 compost-INPF combinations were significantly higher than that recorded from untreated control across the compost types in 2018. The 25:75 and 50:50 compost-INPF combinations gave GYs which were significantly higher than that obtained from the untreated control in 2018/19. In many instances, soil pH and the contents of organic C, NO3, P, K, Na and Zn recorded from treatments with the different mix ratios of compost and INPF were higher than that recorded from the untreated control. Grain yield correlated significantly and positively with the contents of soil NH4 (r = 0.59) and P (r = 0.53) indicating that these nutrients contributed to the final GY. In conclusion, the joint application of compost and INPF at 25:75 and 50:50 ratios appears promising for improving GY. Increase in soil K content suggested the need for a controlled application of WSW compost followed by frequent soil testing exercise to monitor and avoid unnecessary K build-up that may induce the deficiencies of other plant nutrients.

Soil potassium regulation by changes in potassium balance and iron and aluminum oxides in paddy soils subjected to long-term fertilization regimes

Southern China’s paddy soils are poor in potassium (K) and rich in iron (Fe) and aluminum (Al) oxides, both of which are affected by fertilizer application. However, the response of soil K budget to long-term K fertilization and Fe and Al oxides remains unclear, especially in the subsurface horizons in different soil types. Here, four long-term fertilization treatments (no fertilizer, CK; inorganic nitrogen and phosphorus fertilizers, NP; NPK; and the combined NPK and manure, NPKM) were selected to determine the effects of K input and different forms of Fe and Al oxides on soil K status at two soil layers (0–20, surface; and 20–40 cm, subsurface) in red (Ferralsols) and purple (Cambisols) paddy soils across China. Overall, treatments where K fertilizer application was withheld had lower surface soil exchangeable K (EK), non-exchangeable K (NEK), and total K contents than treatments applied with K fertilizer. In contrast, the treatment including K with manure fertilizer increased EK and NEK contents. Regardless of fertilization regimes, the contents of EK and NEK in both soil depths of purple soil were significantly higher than those in their corresponding depths of red soil. Moreover, there were significantly lower EK and NEK contents in the subsurface layer than those in the surface layer of red soil, while no significant differences were observed in purple soil. A positive correlation was obtained between K balances and soil EK contents (P < 0.05) and the slopes of linear regressions in red soil was higher than that in purple soil. A three-way ANOVA showed that the lone and interactive effects of experimental site, fertilization regime, and soil depth significantly influenced the contents of Fe and Al oxides in both soils. The application of NPKM can inhibit the decrease of free Fe and Al oxides in the surface layer of soil and increase the amorphous and chelated Fe and Al oxides, especially in red soil. Redundancy analysis showed that the amorphous Fe and Al oxides were the most important factors for regulating surface soil EK content. The free and chelated oxides were the most important factors for regulating NEK contents in red and purple soils, respectively, particularly in subsurface soil. Our results imply that the combined application of inorganic fertilizer and manure is a viable strategy for improving soil K availability by increasing K balance and regulating the contents and forms of Fe and Al oxides in different depths of paddy soil.

EFFECT OF ORGANIC AND INORGANIC FERTILIZERS OR THEIR COMBINATIONS ON YIELD AND QUALITY COMPONENTS OF OIL SEED SUNFLOWER IN A SEMI-ARID ENVIRONMENT

Producers in semi-arid and highland regions have difficulty in increasing diversity in crop rotations due to unfavorable conditions imposed by cool temperatures, inadequate rainfall, and shorter growing periods. In such conditions, some cultural practices that increase productivity such as fertilization appear as a promising alternative. Fertilization and the form of fertilizer have a substantial influence on sunflower (Helianthus annuus L.) seed yield and quality. The objective of this study was to determine the responses of the oilseed sunflower to organic (vermicompost and leonardite) and inorganic (nitrogen and phosphorus) fertilizers, or their combinations in a highland environment. To this end, the field research was carried out in 2017 and 2018 in Erzurum, Eastern Anatolia, Turkey. In this study, it was found that the organic and inorganic fertilizers alone and their combinations significantly affected all the plant parameters. The highest seed yield (4854 kg ha-1) and oil yield (2114 kg ha-1) were obtained from the combined use of nitrogen and vermicompost. Moreover, the use of vermicompost alone yielded the highest oil content (46.8%). According to the results of this study, combined applications of organic (vermicompost) and inorganic (nitrogen) fertilizers had the highest yield and agronomic characteristics in oilseed sunflower production; so, these applications can be recommended for the similar ecological conditions, that is, short growing season and high altitude.

Effects of nearly four decades of long-term fertilization on the availability, fraction and environmental risk of cadmium and arsenic in red soils

Fertilizers are important for agricultural production because they can effectively promote crop productivity. However, long-term fertilization can cause heavy metal accumulation in soils and crops. This study utilized sequential extraction, the diffusive gradient in the thin films (DGT) technique and risk assessment models to estimate the effects of the longest long-term fertilization (38 years) in China on cadmium (Cd) and arsenic (As) accumulation in soils. The treatments included no fertilization (CK); inorganic nitrogen, phosphorus, and potassium fertilization (NPK); manure fertilization (M); and NPK plus M cofertilization (NPKM). The results indicated that the soils treated with NPKM, M and NPK had significantly increased total and available concentrations of Cd and As after 38 years of long-term fertilization. Cd mainly originates from cattle manure, while As originates from phosphate fertilizer. Sequential extraction results indicated that the application of manure increased the acid/exchangeable fraction (F1) and organic matter-bound fraction (F3) of Cd and As. The risk assessment results showed that the environmental risks of both Cd and As increased during long-term fertilization, and Cd contamination in the soil was at a moderate-high level, while As remained at a relatively low level. According to the calculations of the maximum numbers of years of soil productivity and rice production, Cd was labile and accumulated in the soils, and As was more labile than Cd in terms of accumulating in rice, indicating that the true risk from As in rice is higher than that from Cd. Controlling the heavy metals in fertilizers, mitigating effective amendments, and identifying plant types that accumulate low amounts of contaminants may be good choices for cleaner crop production.