Years Of Continuous Fertilization Research Articles

Soil Acidification Can Be Improved under Different Long-Term Fertilization Regimes in a Sweetpotato-Wheat Rotation System.

Soil acidification is a significant form of agricultural soil degradation, which is accelerated by irrational fertilizer application. Sweetpotato and wheat rotation has emerged as an important rotation system and an effective strategy to optimize nutrient cycling and enhance soil fertility in hilly areas, which is also a good option to improve soil acidification and raise soil quality. Studying the effects of different fertilization regimes on soil acidification provides crucial data for managing it effectively. An eight-year field experiment explored seven fertilizer treatments: without fertilization (CK), phosphorus (P) and potassium (K) fertilization (PK), nitrogen (N) and K fertilization (NK), NP fertilization (NP), NP with K chloride fertilization (NPK1), NP with K sulfate fertilization (NPK2), and NPK combined with organic fertilization (NPKM). This study focused on the soil acidity, buffering capacity, and related indicators. After eight years of continuous fertilization in the sweetpotato-wheat rotation, all the treatments accelerated the soil acidification. Notably, N fertilization reduced the soil pH by 1.30-1.84, whereas N-deficient soil showed minimal change. Organic fertilizer addition resulted in the slowest pH reduction among the N treatments. Both N-deficient (PK) and organic fertilizer addition (NPKM) significantly increased the soil cation exchange capacity (CEC) by 8.83% and 6.55%, respectively, compared to CK. Similar trends were observed for the soil-buffering capacity (pHBC). NPK2 increased the soil K+ content more effectively than NPK1. NPKM reduced the sodium and magnesium content compared to CK, with the highest magnesium content among the treatments at 1.60 cmol·kg-1. Regression tree analysis identified the N input and soil magnesium and calcium content as the primary factors influencing the pHBC changes. Structural equation modeling showed that the soil pH is mainly influenced by the soil ammonium N content and pHBC, with coefficients of -0.28 and 0.29, respectively. Changes in the soil pH in the sweetpotato-wheat rotation were primarily associated with the pHBC and N input, where the CEC content emerged as the main factor, modulated by magnesium and calcium. Long-term organic fertilization enhances the soil pHBC and CEC, slowing the magnesium reduction and mitigating soil acidification in agricultural settings.

Differences in background environment and fertilization method mediate plant response to nitrogen fertilization in alpine grasslands on the Qinghai-Tibetan Plateau

Grassland degradation threatens ecosystem function and livestock production, partly induced by soil nutrient deficiency due to the lack of nutrient return to soils, which is largely ascribed to the intense grazing activities. Therefore, nitrogen (N) fertilization has been widely adopted to restore degraded Qinghai-Tibetan Plateau (QTP) grasslands. Despite numerous field manipulation studies investigating its effects on alpine grasslands, the patterns and thresholds of plant response to N fertilization remain unclear, thus hindering the prediction of its influences on the regional scale. Here, we established a random forest model to predict N fertilization effects on plant productivity based on a meta-analysis synthesizing 88 publications in QTP grasslands. Our results showed that N fertilization increased the aboveground biomass (AGB) by 46.51 %, varying wildly among plant functional groups. The positive fertilization effects intensified when the N fertilization rate increased to 272 kg ha−1 yr−1, and decreased after three years of continuous fertilization. These effects were more substantial when applying ammonium nitrate compared to urea. Further, a machine learning model was used to predict plant productivity response to N fertilization. The total explained variance and mean squared residuals ranged from 49.41 to 75.13 % and 0.011–0.058, respectively, both being the highest for grasses. The crucial predictors were identified as climatic and geographic factors, background AGB without N fertilization, and fertilization methods (i.e., rate, form, and duration). These predictors with easy access contributed 62.47 % of the prediction power of grasses' response, thus enhancing the generalizability and replicability of our model. Notably, if 30 % of yak dung is returned to soils on the QTP, the grassland productivity and plant carbon pool are predicted to increase by 5.90–6.51 % and 9.35–10.31 g C m−2 yr −1, respectively. Overall, the predictions of this study based on literature synthesis enhance our understanding of plant responses to N fertilization in QTP grasslands, thereby providing helpful information for grassland management policies.Conflict of interest: The authors declare no conflict of interest.

Changes in soil phosphorus (P) fractions and P bioavailability after 10 years of continuous P fertilization

Phosphorus fertilization modify soil P fractions differing in availability, but little is known about bioavailability of these pools for the crops when increasing P fertilizer rates in the medium term. Our objectives were to evaluate: i) changes in Bray-1 P content (extracted with 0,03 M NH4F and 0,1 M HCl) and soil P fractions as estimated by physical (Cambardella and Elliot method, POM-P) and chemical fractionation (Hedley method), ii) the relationship between these fractions and P bioavailability quantified in a test crop, and iii) the interaction with sulfur (S) fertilization after 10 years of continuous P and S fertilization. Soil samples were taken after 10 years in an experiment that followed a maize - full season-soybean - double-cropped wheat /soybean sequence that received P and S fertilization when cereals were sown. Treatments consisted of a factorial combination of three P rates (0, 20, and 40 kg P ha−1) and four S rates (0, 12, 24, and 36 kg S ha−1) applied to cereals from 2000 to 2010. After that, a maize used as a test crop was sown and P uptake was considered as bioavailable P. Soil samples were taken before sowing the test crop, and P in soil was fractionated chemically by the Hedley method and physically by wet sieving. After 10 years, when P fertilizer was not applied, soil Bray-1 P decreased 50 % respect to the initial P values, and increased up to 2.3 times when evaluating the highest P fertilizer rate. P fertilization did not change in POM-P. P soil labile (NaHCO3-Pi) and moderately labile (NaOH- Pi and HCl 1 M- Pi) inorganic fractions increased 83 %, 50 %, and 22 % in response to P addition, representing an increase of 4.2, 4.9, and 4.5 mg kg−1 of these fractions per 100 kg of applied P. Likewise, these fractions were related with P uptake in the maize test crop with 1.6, 1.5, and 1 kg of P uptake ha−1 in mg kg−1 increase in each of these fractions, respectively. Then, these fractions may be responsible for the legacy-P after 10 years of continuous fertilization in a Luvic Phaeozem of the Pampas region.

Positive effects of organic fertilizers and biofertilizers on soil microbial community composition and walnut yield

Different fertilization regimes differentially impact the physicochemical properties, diversity, and ecosystem functioning of soil microbial communities. However, there is little research on the relationship between soil quality, microbial diversity, and crop production under different long-term fertilization regimes, especially on woody plants. Therefore, in this study, we investigated changes in the soil microbial communities of walnut orchards after nine years of continuous fertilization (no fertilizer, only chemical fertilizer, chemical + organic fertilizer, chemical + biofertilizer, and chemical + organic + biofertilizer), and analyzed the link between fertility improvement and yield increase from a microbial perspective. The results showed that the soil quality index was strongly correlated with organic fertilizers and biofertilizers addition, and exhibited a significant relationship with walnut yield. Furthermore, the addition of organic fertilizers or biofertilizers promoted the enrichment of microorganisms beneficial to soil fertility, crop growth (Bacillus spp.) and soil bioremediation (Solicoccozyma spp.) and decreased the amounts of Fusarium spp. in the walnut orchard soil. Moreover, structural equation modeling indicated strong and positive relationships between walnut yield and the diversity of the keystone microbial communities. Overall, the results confirm the feasibility of using multiple fertilizer blends to improve soil fertility and reveal the fundamental role of fungal diversity in maintaining economic forest tree production.

Long-term fertilization and manuring with different organics alter stability of carbon in colloidal organo-mineral fraction in soils of varying clay mineralogy

Majority of organic matter is bound to clay minerals to form stable colloidal organo-mineral fraction (COMF) in soil. Stability of carbon (C) in COMF is crucial for long-term C sequestration in soil. However, information on the effect of long-term fertilization and manuring with various organic sources on C stability in such fraction in soils with varying clay mineralogy is scarce. The present study was, therefore, carried out to assess the effect of thirty-one years of continuous fertilization and manuring with different organics on C-stability in COMF extracted from an Inceptisol, a Vertisol, a Mollisol, and an Alfisol. The treatments comprised of control (no fertilization), 100% NPK (100% of recommended N, P and K through fertilizer), 50% NPK+ 50% of recommended N supplied through either farm yard manure (FYM) or cereal residue (CR) or green manure (GM). The stability of C (1/k) in COMF was determined from desorption rate constant (k) of humus-C by sequential extraction and correlated with extractable amorphous Fe-Al-Si-oxides, and crystallite size of illite minerals. Long-term fertilization and manuring with the above sources of organic altered the contents of amorphous Fe-Al-Si-oxides, and decreased the crystallite size of illite in all the soil orders. Fifty percent substitution of fertilizer N by various organics significantly increased C-stability in COMF by 27–221% (mean 111%) over full dose of NPK (100% NPK). Smectite dominating Vertisol exhibited highest stability of C followed by the Mollisol, the Inceptisol and the Alfisol. Stability of such C in soil was correlated positively with the amount of amorphous Fe and Al oxides but negatively with crystallite size of illite (r = −0.46, P < 0.01). Application of NPK + GM or NPK + FYM in Inceptisol, Vertisol and Mollisol and NPK + GM or NPK + CR in Alfisol emerged as the best management practices for higher stabilization of C in COMF for long-term C sequestration.

Twenty-six years of chemical fertilization decreased soil RubisCO activity and changed the ecological characteristics of soil cbbL-carrying bacteria in an entisol

Soil autotrophic bacteria are important for sequestrating atmospheric CO2 and thus contribute to the global carbon cycle. However, information is limited on how chemical fertilization can alter the composition of soil autotrophic bacteria. In this study, the cbbL gene (a key gene in the Calvin-Benson-Bassham cycle that encodes the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase, RubisCO) was used to study the abundance and composition of autotrophic bacteria in an entisol with 26 years of continuous fertilization. In this process, five chemical fertilization regimes were examined: without fertilization control (CT), nitrogen and phosphorus fertilization (NP), N and potassium fertilization (NK), PK fertilization (PK), and NPK fertilization (NPK). The results showed that after the 26-year (1991–2017) period, the CT with a neutral pH (7.55) had a higher RubisCO activity than did the chemical fertilizer treatments, but the cbbL abundance was the lowest under CT. Soil RubisCO activity positively correlated with soil pH (R2 = 0.67, P < 0.001); soil cbbL abundance significantly positively correlated with soil available N (R2 = 0.54, P < 0.01) and significantly negatively correlated with pH (R2 = 0.30, P < 0.05). Meanwhile, the soil RubisCO activity significantly negatively correlated with cbbL abundance (R2 = 0.67, P < 0.001). In addition, the alpha-diversity of cbbL was lowest under CT, indicating a positive effect of fertilization on the soil cbbL diversity. In conclusion, a 26-year long-term chemical fertilization changed the community structure of soil cbbL-carrying bacteria, and soil pH and available N played crucial roles in controlling the ecological properties of soil cbbL-carrying bacteria.

The effect of 34-year continuous fertilization on the SOC physical fractions and its chemical composition in a Vertisol

Reports regarding the effects of long-term organic and inorganic fertilization on the quantity and quality of soil organic carbon (SOC), particularly in Vertisols, are scarce. In this study, we combined SOC physical fractionation with 13C NMR spectroscopy technology to investigate the effect of 34 years of continuous fertilization on the SOC physical fractions and its chemical composition of 0–20 cm soil layer in a Vertisol. This study consisted of six treatments: no fertilization (control), chemical nitrogen, phosphorus and potassium fertilizers (NPK), low and high amounts of straw with chemical fertilizers (NPKLS and NPKHS), and pig or cattle manure with chemical fertilizers (NPKPM and NPKCM). Over 34 years of continuous fertilization, the SOC sequestration rate was from 0.08 Mg C ha−1 yr−1 in the control treatment to 0.66 Mg C ha−1 yr−1 in the NPKCM treatment, which was linearly related with the C input (P < 0.01). Of the five SOC physical fractions, two silt plus clay fractions (S + C_M, S + C_mM) dominated 74–92% of SOC, while three POM fractions (cPOM fPOM and iPOM) were only 8–26%. The two manure application treatments significantly increased all the SOC physical fractions except for the silt plus clay fraction within macroaggregates (S + C_M) compared with NPK treatment (P < 0.05), which was dependent on the larger amount of C input. Also, the two manure application treatments increased the levels of alkyl C and aromatic C but decreased O-alkyl C (P < 0.05), whereas the straw application (NPKLS and NPKHS) had no impact on the C functional groups (P > 0.05). Overall, the combination of animal manure with inorganic fertilization could enhance the SOC sequestration and alter its quantity and quality in Vertisols.

Plant Functional Diversity Can Be Independent of Species Diversity: Observations Based on the Impact of 4-Yrs of Nitrogen and Phosphorus Additions in an Alpine Meadow.

Past studies have widely documented the decrease in species diversity in response to addition of nutrients, however functional diversity is often independent from species diversity. In this study, we conducted a field experiment to examine the effect of nitrogen and phosphorus fertilization ((NH4)2 HPO4) at 0, 15, 30 and 60 g m-2 yr-1 (F0, F15, F30 and F60) after 4 years of continuous fertilization on functional diversity and species diversity, and its relationship with productivity in an alpine meadow community on the Tibetan Plateau. To this purpose, three community-weighted mean trait values (specific leaf area, SLA; mature plant height, MPH; and seed size, SS) for 30 common species in each fertilization level were determined; three components of functional diversity (functional richness, FRic; functional evenness, FEve; and Rao’s index of quadratic entropy, FRao) were quantified. Our results showed that: (i) species diversity sharply decreased, but functional diversity remained stable with fertilization; (ii) community-weighted mean traits (SLA and MPH) had a significant increase along the fertilization level; (iii) aboveground biomass was not correlated with functional diversity, but it was significantly correlated with species diversity and MPH. Our results suggest that decreases in species diversity due to fertilization do not result in corresponding changes in functional diversity. Functional identity of species may be more important than functional diversity in influencing aboveground productivity in this alpine meadow community, and our results also support the mass ratio hypothesis; that is, the traits of the dominant species influenced the community biomass production.

Effects of nitrogen and phosphorus fertilization on soil carbon fractions in alpine meadows on the Qinghai-Tibetan Plateau.

In grassland ecosystems, N and P fertilization often increase plant productivity, but there is no concensus if fertilization affects soil C fractions. We tested effects of N, P and N+P fertilization at 5, 10, 15 g m−2 yr−1 (N5, N10, N15, P5, P10, P15, N5P5, N10P10, and N15P15) compared to unfertilized control on soil C, soil microbial biomass and functional diversity at the 0–20 cm and 20–40 cm depth in an alpine meadow after 5 years of continuous fertilization. Fertilization increased total aboveground biomass of community and grass but decreased legume and forb biomass compared to no fertilization. All fertilization treatments decreased the C:N ratios of legumes and roots compared to control, however fertilization at rates of 5 and 15 g m−2 yr−1 decreased the C:N ratios of the grasses. Compared to the control, soil microbial biomass C increased in N5, N10, P5, and P10 in 0–20 cm, and increased in N10 and P5 while decreased in other treatments in 20–40 cm. Most of the fertilization treatments decreased the respiratory quotient (qCO2) in 0–20 cm but increased qCO2 in 20–40 cm. Fertilization increased soil microbial functional diversity (except N15) but decreased cumulative C mineralization (except in N15 in 0–20 cm and N5 in 20–40 cm). Soil organic C (SOC) decreased in P5 and P15 in 0–20 cm and for most of the fertilization treatments (except N15P15) in 20–40 cm. Overall, these results suggested that soils will not be a C sink (except N15P15). Nitrogen and phosphorus fertilization may lower the SOC pool by altering the plant biomass composition, especially the C:N ratios of different plant functional groups, and modifying C substrate utilization patterns of soil microbial communities. The N+P fertilization at 15 g m−2 yr−1 may be used in increasing plant aboveground biomass and soil C accumulation under these meadows.

Effects of fertilization on the relations of diameter at breast height between different-aged ramets of Phyllostachys edulis population

Aims Clonal plants are physiologically integrated, allowing translocation of photosynthates, water, nutrients and other substances between connected ramets within a clone. This suggests that the sizes of ramets of different ages may be correlated. So far, however, little is known about the effects of fertilization on the size relationships between ramets of different ages. In this study, we aim to examine how fertilization affects the relations of diameter at breast height(DBH) between ramets of different ages in the giant clonal bamboo Phyllostachys edulis. Methods We established 112 20 m × 30 m plots of P. edulis in Longquan City, Zhejiang Province, China. Among them, 46 plots were fertilized only in 2008, 49 fertilized in five consecutive years from 2004 to 2008, and 17 unfertilized(the control). We measured DBH of ramets of one, three and five years old in each plot in 2009. The relations of DBH between ramets of different ages in different fertilization treatments were examined using allometric scaling by the standardized major axis(SMA) analysis, and that were also analyzed by multiple linear regression. Important findings The DBH of the 1-year-old ramets was significantly greater than that of the 5-year-old ones in the 5-year fertilization plots, while no significant difference was found in the 1-year fertilization plots. Under different fertilization treatments, the slopes of SMA(0.88–1.10) for the relations of DBH between ramets of one, three and five years old were not significantly different from 1.00(p 0.05), suggesting isomeric growth relationships. Compared to the control(unfertilization), fertilization in one or five years did not change the slope of SMA. However, fertilization in five years increased the intercept of SMA, indicating that continuous fertilization could result in greater DBH increment in the 1-year-old ramets. The multiple linear stepwise regression analysis indicated that 3-year-old ramets could greatly influence DBH of the newly produced ramets, and that the effect of DBH of the 5-year-old ramets on that of the 1-year-old ramets increased after five years of continuous fertilization.

Effects of Irrigation and Fertilization on Soil Microbial Biomass and Functional Diversity

Optimal water and nutrient treatment effects on soil mi-crobial characteristics, including microbial functional diversity and mi-crobial biomass carbon (C) and nitrogen (N) were assessed at a loblolly pine plantation on a Sandhills site after 6 years of continuous fertilization and irrigation. Fertilization significantly increased soil C and N and microbial C and N. Irrigation significantly increased soil C and N, and microbial C. Fertilization, irrigation, and their interaction changed soil microbial selection of carbon compounds, but did not influence the numbers of carbon compounds utilized by soil microbes, as measured by the BIOLOG method suggesting that soil microbial species may have changed. The increases in soil microbial biomass and soil C and N indicate that the fertilization and irrigation treatments have had a positive effect on soil productivity on this very sandy site.