Long-term Application Of Inorganic Fertilizers Research Articles

Active Soil Organic Carbon Pools Decrease with Increased Time since Land-Use Transition from Rice Paddy Cultivation to Areca Nut Plantations under the Long-Term Application of Inorganic Fertilizer

Many croplands in the tropics of China have been converted over the last decades into areca nut plantations due to their high economic returns. This land-use transition was accompanied by changes in agricultural practices such as soil moisture regimes and fertilizer inputs, which may affect soil organic carbon (SOC) and its fractions, especially in tropical soils with low fertility and high nitrogen loss. Yet, how the time since land-use transition from rice paddy cultivation to areca nut plantations affects soil carbon dynamics and their underlying mechanisms in the tropics of China remains elusive. Here, areca nut plantation soils with different ages (2, 5, 10, 14, and 17 years) and paddy fields in the tropical region of China were investigated. The study result indicates that the contents of dissolved organic carbon (DOC), particulate organic carbon (POC), easily oxidized organic carbon (EOC), light organic carbon (LFOC), and microbial biomass carbon (MBC) decreased significantly with increased time since land-use transition from rice paddy cultivation to areca nut plantations. Similarly, the ratios of DOC/SOC, MBC/SOC, POC/SOC, LFOC/SOC, and EOC/SOC decreased significantly with increased time since land-use transition. Compared with the paddy soil, the carbon pool management index decreased by 36.6–76.7% under the areca nut plantations, concluding that increasing the time since land-use transition from rice paddy cultivation to areca nut plantations with high application rates of chemical fertilizers resulted in reduced soil active carbon fractions and SOC supply capacity. Therefore, agricultural practices such as the use of organic fertilizers should be applied to improve the soil’s ability to supply organic carbon in managed plantation ecosystems in the tropics of China.

Impact of long-term application of inorganic fertilizers and organic manure on wheat yield and available phosphorous contents in a vertisol under soybean-wheat cropping sequence

Impact of long-term application of inorganic fertilizers and organic manure on wheat yield and available phosphorous contents in a vertisol under soybean-wheat cropping sequence

Effects of long-term application of inorganic fertilizers and organic amendments on the turnover rates of fractionated soil organic carbon and their determining factors in paddy fields

ABSTRACT To investigate how the long-term application of inorganic fertilizer and organic amendments affects the turnover rates of organic matter in physico-chemically fractionated components in paddy soils and how their rates are related to their amounts, we studied the effect of variable management of inorganic fertilizer and organic amendments for > 50 years on the ∆14C values of accumulated soil organic carbon (SOC) in fractionated components of 5 soil samples from three paddy fields. SOC was fractionated into four components based on their physico-chemical properties: (1) light fraction (LF) derived from plant residues, (2) heavy fraction (HF) containing stable aggregates, (3) oxidizable fraction (OxF) and (4) non-oxidizable fraction (NOxF) forming organo-mineral complexes with fine-textured minerals. The ∆14C values were determined by accelerator mass spectrometry using graphitized samples. The ∆14C values of SOC in NOxF (from −305‰ to − 90.5‰) were much lower than those of HF (from −123‰ to − 3.7‰) and OxF (from −215‰ to 21.0‰). Lowest values for NOxF suggested slowest turnover rates as expected, and higher and comparable values for OxF and HF implied much faster turnover rates of SOC in OxF compared with upland soils. This could be one of the characteristics of SOC dynamics in paddy soils, probably reflecting repeated puddling of plow layer soils. ∆14C values in all the fractions increased in response to the application of inorganic fertilizer and organic amendments, suggesting faster turnover rate. Soils with clayey and weathered characteristics had the lowest ∆14C values, or slowest turnover rates among the study fields. The relationship between the ∆14C value and the amount of accumulated C for HF, OxF and NOxF indicated that the more the SOC accumulated, the faster the turnover rate of the SOC was, regardless of the fractions, and the relationship of the HF was considerably different from those of OxF and NOxF. In conclusion, these results can be the basis for understanding the C dynamics and for improving soil fertility status and soil C sequestration in paddy soils.

Effects of long-term application of inorganic fertilizer and organic amendments on the amounts of fractionated soil organic carbon and their determining factors in paddy fields

ABSTRACT To investigate how the long-term application of inorganic fertilizer and organic amendments affects the accumulation of organic matter in physico-chemically fractionated components in paddy soils and how the accumulation is determined by soil properties and anthropogenic carbon input, we studied the effect of variable management of inorganic fertilizer and organic amendments for > 50 years on the amounts of accumulated soil organic carbon (SOC) in fractionated components in three paddy fields. SOC was fractionated into four components based on their physical and chemical properties: (1) light fraction (LF) derived from plant residues, (2) heavy fraction (HF) containing stable aggregates, (3) oxidizable fraction (OxF) and (4) non-oxidizable fraction (NOxF) forming organo-mineral complexes with fine-textured minerals. On average, the amount and percentage of accumulated C in the four fractions were as follows: OxF (6.63 gC kg−1 soil, 46%) > NOxF (5.32, 35) > LF (1.68, 12) > HF (1.12, 7.2), suggesting about 80% of SOC was in fine, stable fractions. The amount of accumulated C in all fractions increased slightly with the application of inorganic fertilizer, while it increased considerably with the use of organic amendments. In addition, the application of fertilizers and amendments raised the proportion of C content in LF and HF, which are labile and related to soil fertility. Stepwise multiple regression analysis using two principal component analysis scores of soil properties and anthropogenic C input further revealed that the labile fractions (LF and HF) were more strongly determined by the management of fertilizers and amendments, while the stable fractions (OxF and NOxF) were more strongly determined by soil-specific properties, mainly the amorphous nature of the soil. These results indicate that the use of certain amounts of organic amendments would be recommended to carry out rational management to improve soil fertility and C sequestration in paddy fields, with the application of amorphous minerals as an additional option.

Effect of Long-Term Application of Inorganic Fertilizers, Organic Manure, and Lime on Different Forms of Potassium in Soil under Maize-Wheat Cropping System

The field study was undertaken with the major emphasis on potassium fractionation and its contribution in acid alfisol soils as affected by adoption of continuous cropping, fertilization, and manuring under maize-wheat cropping system in same field over 62 years of crop cycles. The experiment consisted of fourteen treatments, replicated thrice times in a randomized block design, out of which nine treatments were selected for the present study. The selected treatments were as follows - control, T2-100% N, T3- FYM, T4-100% NP, T5-100% NPK, T6- 1/2(N+FYM) + P(A-X/2) + K(B-Y/2) (INM), T7-100% NPK + Lime where the lime application in LR once in 4 years, T8-Lime+ FYM+ P(A-X) + K(B-Y), T9-Lime+N. Surface soil (0-15cm) and subsurface soil (16-30 cm) samples were collected after the harvest of wheat in 2017-18 to observe the initial Physico-chemical properties. Different fractions of potassium, viz., water-soluble K, exchangeable K, available K, 1NHNO3K, non-exchangeable K, Lattice K, and Total K were analyzed for the study. There was a significant difference among the different treatments with respect to potassium fractions in 0-15 cm, and 16-30 cm layers. Moreover, K fractions were significantly decreased with increasing depth of soil. Results showed that the percentage contribution of different forms of K with regard to the total K in surface soil and subsurface soil followed as: Lattice K (68.75-78.11%) > Non – Exchangeable K (19.15-25.49%) > Exchangeable K (1.65-2.45%) >Water soluble K (0.18-0.62%). Application of N and P without K caused depletion of soil, water-soluble K, available K, exchangeable K, non-exchangeable K, and lattice K because of continuous omission of potassium content during the all crop growing stages or the simultaneous leaching nature of residual potassium under same field of the experiment. Therefore, the present investigation stresses the vital importance of the inclusion of organic manure and lime in the fertilizer schedule to maintain soil K dynamics over the long run under the maize-wheat cropping system.

Effects of Agricultural Waste Application on Soil Carbon Emission in Newly Cultivated Land

Cultivated land is an important resource to ensure food production and food security. However, the low degree of soil ripening, poor soil and lack of organic matter are common problems in newly cultivated land. Fertilization can effectively improve the physical properties of soil, improve soil nutrients and fertility, but long-term application of inorganic fertilizer will cause soil compaction or even degradation. Returning agricultural waste to the field can not only increase soil fertility and effectively improve soil structure, but also change soil carbon emissions. In this paper, the benefits of straw returning and livestock manure composting and their potential effects on soil carbon emissions were summarized to provide ideas for improving the fertility of new cultivated land.

The Green Manure (Astragalus sinicus L.) Improved Rice Yield and Quality and Changed Soil Microbial Communities of Rice in the Karst Mountains Area

The use of green manure plants for soil restoration is a viable agricultural practice that can mitigate soil degradation and biodiversity loss caused by the long-term application of inorganic fertilizers. However, the effects of green manure on soil microbial communities, rice yield, and quality in the karst mountains are largely unknown. The effects of no chemical fertilizer, chemical fertilizer, chemical fertilizer + different Astragalus sinicus L. (Chinese milk vetch, CMV) treatments on the microbial community, soil enzyme activities, soil nutrient content, and crop yield were investigated through field experiments. A moderate application of chemical fertilizer with green manure can increase chlorophyll content, increase effective rice spikes, positive impact on rice yield, and increase crude protein, etc. Additional application of the moderate amount of CMV can increase alkali-hydrolyzable nitrogen and available phosphorus (a significant increase of 54.87–72.65%), improve microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) (CFMV2 significantly increased by 22.16%), improve soil urease and phosphatase activities, and the urease activity increased by 43.43–69.24% with CMV application compared to CK. Moreover, all bacterial communities were dominated by three major phyla (Proteobacteria, Chloroflexi, and Acidobacteria), where the application of chemical fertilizer with CMV increased the ratio of abundance of Proteobacteria and Acidobacteria in rice soils, and the effect of chemical fertilizer application on the dominant bacteria was regulated to some extent by additional green manure application, which may have a beneficial effect on rice yield. Therefore, we conclude that the rational use of chemical fertilizers with CMV (22,500 kg ha−1) in karst landscapes is one of the effective measures to achieve efficient and sustainable use of rice fields.

Effects of organic fertilizer proportion on the distribution of soil aggregates and their associated organic carbon in a field mulched with gravel

Gravel and sand mulching is an indigenous technology that has been used for increasing soil temperature and improving crop yield and water use efficiency for at least 300 years in northwestern China. However, long-term application of inorganic fertilizer with gravel and sand mulch could decrease the soil organic carbon content, and how to improve soil fertility under gravel and sand mulching remains largely unknown. Thus, we evaluated the effects of the application of inorganic (chemical) and organic (manure) fertilizers on the distribution of soil aggregates and their associated organic carbon in a field mulched with gravel and sand. A 5-year (2014–2018) field experiment was conducted in the arid region of northwestern China. Total organic carbon (TOC), permanganate oxidizable carbon (POC), TOC reserves in soil aggregates with different particle sizes, and watermelon (Citrullus lanatus) productivity in gravel-mulched fields were analysed for the following six fertilization modes: no N fertilizer input as a control (CK), N fertilizer without organic fertilizer (CF), and organic fertilizer replacing 25%, 50%, 75%, and 100% of mineral nitrogen (recorded as OF-25%, OF-50%, OF-75% and OF-100%, respectively). The results showed that, higher manure to nitrogen fertilizer ratios were positively correlated with the percentage of soil macroaggregates (> 0.25 mm), mean weight diameter (MWD), TOC and POC concentrations, and their ratios in different particle sizes. Compared with CF, the treatments with 50% to 100% organic fertilizer significantly increased TOC storage (5.91–7.84%) in the soil profile (0–20 cm). Moreover, the CF treatment did not increase SOC concentrations or TOC storage, compared with CK. The fruit yield (2014–2018) of watermelon significantly increased by an average of 31.38% to 45.70% in the treatments with 50% to 100% organic fertilizer, respectively, compared with CF. Our results suggest that the partial replacement of chemical fertilizer with organic manure (OF-50%, OF-75% and OF-100%) could increase the proportion of macroaggregates, POC and TOC concentrations, and TOC stock in aggregates with different particle size and improve the yield of watermelon in the gravel fields of arid northwestern China mulched with gravel and sand.

Assessing Soil Physical and Chemical Properties Under Long Term Fertilization After Forty-Eight Years in North-Western Himalayas

ABSTRACT The present investigation was carried out in an on-going long-term fertilizer experiment, initiated during 1972 at experimental farm of Department of Soil Science, Choudhary Sarwan Kumar Himachal Pradesh Krishi Vishwavidyalaya Palampur, to study the long-term effect of fertilizers and amendments on soil physical and chemical properties in an acid Alfisol under maize–wheat cropping system. The experiment consisted of 11 treatments with 3 replications with randomized block design. The soil of the experimental site was silt loam and classified taxonomically as “Typic Hapludalf” (Subgroup). Long-term use of integrated nutrient management practices significantly improved the available Nitrogen, Phosphorus and Potassium as compared to control. Effect of long-term application of inorganic fertilizers and amendments on soil chemical properties was studied. Soil organic carbon content was increased in 100% Nitrogen, Phosphorus and Potassium + Farm Yard Manures applied plots. Application of inorganic fertilizers along with Farm Yard Manures increased the Mean weight diameter (MWD) and Geometric mean weight diameter (GMD) over control. The available Nitrogen, Phosphorus and Potassium and Diethylenetriamine pentaacetate (DTPA) extractable micronutrients cation were optimum in 100% Nitrogen, Phosphorus and Potassium + Farm Yard Manures applied treatments.

Long term combined fertilization and soil aggregate size on the denitrification and community of denitrifiers

Balanced fertilization strategies that combine the use of organic and inorganic fertilizers have been adopted to increase soil fertility and crop yield and to safeguard environment. However, knowledge on the influence of these fertilization strategies on microbe-mediated nitrogen cycling in the agricultural ecosystems remains limited. We analyzed the denitrifiers with nitrite reductase genes (nirK and nirS) in three soil aggregate classes (large macroaggregates, >2 mm; small macroaggregates, 0.25–2 mm; and microaggregates, <0.25 mm) in response to long-term application of inorganic fertilizers (NPK), NPK plus straw (NPKS), and NPK plus manure (NPKM) in the fluvo-aquic soil of North China Plain. Both fertilization and aggregate size had significant effects on the nirK and nirS gene abundances and soil potential denitrification activity (PDA). PDA in the combined fertilizer-treated soils (NPKS and NPKM treatments) was two times more than that in inorganic NPK-treated soil. PDA dramatically increased in small macroaggregates and microaggregates of NPKS treatment. The nirS gene abundance was significantly higher than that of the nirK gene abundance, and NPKS and NPKM treatments increased the nirS to nirK ratio in bulk soils and in microaggregates compared with NPK treatment and control. Correlation analysis and automatic linear modeling revealed a primary correlation between PDA and abundance of nirS-type denitrifiers. Soil properties, such as SOC, pH and TN, significantly affected the community structure of nirK- and nirS-type denitrifiers while only aggregate size significantly influenced the composition of nirK-type denitrifiers. Taken together, our results suggest that long-term combined fertilization increased the denitrification potential in small macroaggregate and microaggregate classes, and the increased gene abundance and the shift community structures of nirS- and nirK-type denitrifiers were potentially responsible for an increase in the promoted denitrification.

Effect of long-term application of inorganic fertilizers, farm yard manure and lime on wheat (Triticum aestivum L.) productivity, quality and nutrient content in an acid alfisol

The effect of long-term addition of fertilizers and amendments on productivity, quality and nutrient content of wheat (Triticum aestivum L.) in an acid Alfisol was evaluated in field experiment at the research farm of the Department of Soil Science, Chaudhary Sarwan Kumar Himachal Pradesh Krishi Vishvavidyalaya (CSKHPKV) Palampur, Himachal Pradesh (India). The Long-Term Fertilizer Experiment was initiated during 1972 in randomized block design (RBD) with 11 treatments which were replicated three times. The soil of the experimental area was silt loam and classified taxonomically as “Typic Hapludalf”. The highest productivity of wheat (2822 kg ha−1) was recorded in the treatment comprising the recommended dose of fertilizer along with farmyard manure (FYM) @ 10t ha−1 and was statistically comparable with 100% NPK + lime (2589 kg ha−1). Continuous application of nitrogen (N) alone through urea (100%) in an acid alfisol has resulted in zero yield of wheat. Application of FYM and lime along with recommended doses of fertilizers improved all the crop quality parameters viz. crude protein, gluten, ash, fat, fiber and carbohydrate as compared to control and imbalanced fertilization for the last 45 years led to decline in crop quality parameters. Nutrient content in wheat grain i.e., phosphorus (P), magnesium (Mg) and iron (Fe) content was also the highest in FYM amended treatment and lowest in control. Whereas, calcium (Ca) content was the highest in lime amended plot and the lowest in control.

Effect of long-term organic amendments on the full-range soil water retention characteristics of a Vertisol

Enhancement of soil water holding capability is of great interest for the management of agro-ecosystems to increase water use efficiency and crop yields. Application of organic amendments has been reported to affect the wet range of the soil water retention characteristic (SWRC, pF ≤ 4.2) differently and knowledge of the impact on the dry range of the SWRC (pF > 4.2) is limited. In this study, we evaluated the effect of 33 years application of inorganic fertilizer and organic amendments, including wheat straw, cow and pig manure on the full range of the SWRC of a Vertisol. Results showed that long-term application of inorganic fertilizer did not significantly affect soil water retention. The addition of organic amendments, i.e. wheat straw, pig or cow manure in combination with inorganic fertilizer significantly increased the wet range of the soil water retention, which was attributed to improved soil structure by increased SOC content. However, plant available water content was not significantly improved by organic amendments. Application of organic amendments decreased or had no effect on soil water retention at pF > 5.5, indicating the hygroscopic water was less impacted by SOC content. Our results showed that the effects of organic amendments mainly improved the retention of the capillary water but not the adsorption of hygroscopic water. This provides new insights on the understanding of water behaviors in Vertisols.

Nitrogen fertilizer is a key factor affecting the soil chemical and microbial communities in a Mollisol.

Microbial communities drive geochemical cycles in soils. Relatively few studies have assessed the long-term impacts of different types of soil amendments under field conditions in long-term experiments. The response of soil microbial organisms in a Mollisol cultivated with maize for 35 years was examined. Treatments involved the use of N, P, and K fertilizers and two doses of straw residue in isolation or combined. Real-time PCR and Illumina MiSeq sequencing methods were used to characterize the microbial community. The results showed that addition of nitrogen fertilizers decreased soil pH, but this was mitigated when a high dose of straw was also incorporated. Long-term application of inorganic fertilizers was able to alter the abundance of functional soil microbial population. Application of inorganic N fertilizer resulted in distinctive changes on N-cycle microorganisms. Phosphate-solubilizing functional genes abundance was lower in plots with no phosphate fertilizer. Sequencing analysis showed that the presence or absence of N in the fertilizer mix is a key factor affecting bacterial community diversity of agricultural soil, and pH, total organic C, and total N show a high correlation with bacterial community composition. Nitrogen addition increased the N concentration in the soil, which could cause changes in the soil pH and change the soil bacterial community. Our findings proved that interaction of N fertilizer with other fertilizers can affect microbial communities.

Water extractable organic carbon and nitrogen and their stable isotopes from long-term experiment in a Japanese rice paddy

Hot water- and water-extracted organic matter was extracted from soil samples collected after a 31-year long-term experiment which aimed to assess the effect of different fertilization strategies (inorganic fertilizers and organic matters) commonly used for paddy rice cultivation in Yamagata, northeastern Japan. The ratio of soil to extracted water was 2:3. The amounts of hot water-extracted organic carbon and nitrogen (HWEOC and HWEN) at 80 o C and 16 hours, water-extracted organic carbon and nitrogen (WEOC and WEN) at room temperature, and their δ 13 C and δ 15 N were measured from the five fertilizer treatment plots as [1) PK, 2) NPK, 3) NPK + 6 Mg ha -1 rice straw (RS), 4) NPK + 10 Mg ha -1 rice straw compost (CM1), and 5) NPK + 30 Mg ha -1 rice straw compost (CM3)], for surface (0-15 cm) and subsurface (15-25 cm) layers. HWEOC and WEOC accounted for an average of about 1.5 1 and 0.66% of SOC, while HWEN and WEN accounted for an average of about 1.09 and 0.40% of soil TN, respectively. About 90% of the extracted N was organic form among all treatments . The values of δ 13 C for HWEOC and WEOC ranged from -28.2 to -26. 5 ‰ and from -28.3 to -27.0‰, similar to the original rice straw and rice straw compost , and lower than the value of original soil at -22.5 ‰. The values of δ 15 N of HWEN, WEN and bulk soil ranged from 0. 8 to 3. 8 ‰, from 1.0 to 4.0‰, and from 0. 8 to 2. 8 ‰, respectively. It was clear that δ 15 N decreased in RS but increased in CM3 treatments. Our results indicated that the amounts of h ot water- and water-extracted organic matter were affected by long-term application of inorganic fertilizers and organic matter s remarkably. However, the values of δ 13 C for HWEOC and WEOC were not different among 5 treatments, but values of δ 15 N of HWEN and WEN were affected by RS and CM3 applications clearly .

Long-term animal manure application promoted biological binding agents but not soil aggregation in a Vertisol

To improve soil aggregation through proper fertilization is very important for enhancing soil quality and crop productivity. However, the response of soil aggregation varies with the fertilization practices. The objective of this study was to determine the effects of long-term application of inorganic fertilizer, straw and manure on water-stable aggregate distribution (>2 mm, 0.25–2.0 mm, 0.053–0.25 mm, and <0.053 mm), soil organic carbon (SOC), glomalin-related soil proteins (GRSP) and microbial biomass carbon (MBC) as the major biological binding agents in a Vertisol. The fertilization experiment established in 1982 is composed of six treatments as follows: no fertilization (Control), balanced inorganic fertilizer (NPK), low and high amount of straw plus inorganic fertilizer (NPKLS and NPKHS), and animal manure (both pig and cattle) plus inorganic fertilizer (NPKPM and NPKCM). Long-term straw and manure fertilization significantly increased SOC, GRSP and MBC (P < 0.05), while the application of the two animal manures also increased dispersing agents like exchangeable Na+. Consequently, the straw incorporation promoted the formation of >2 mm macroaggregates significantly (P < 0.05) but the two animal manures did not (P > 0.05). The SOC, GRSP and MBC played an important role in the formation and stabilization of 0.25–2.0 mm aggregates. Our results indicate that animal manure may degrade soil structure due to the high salt content but straw incorporation is a judicious practice for sustainable agriculture in the Vertisol.

Changes in the pH, EC, available P, SOC and TN stocks in a single rice paddy after long-term application of inorganic fertilizers and organic matters in a cold temperate region of Japan

The objective of this study was to determine the changes in the main soil chemical properties including pH, electrical conductivity (EC), available phosphorus (P), soil organic carbon (SOC) and total nitrogen (TN) stocks after long-term (31 years) additions of two types of organic matters—rice straw and rice straw compost, combined with NPK fertilizers in single rice paddy in a cold temperate region of Japan. A long-term experiment on combined inorganic fertilizers and organic matters in paddy rice cultivation began in May 1982 in Yamagata, northeastern Japan. After the 31st harvest, soil samples were collected from five treatments [(1) PK, (2) NPK, (3) NPK + 6 Mg ha−1 rice straw (RS), (4) NPK + 10 Mg ha−1 rice straw compost (CM1), and (5) NPK + 30 Mg ha−1 rice straw compost (CM3)] at five soil depths (0–5, 5–10, 10–15, 15–20, and 20–25 cm). Soil chemical properties of pH, EC, available P, SOC, and TN were analyzed. The pH decreased significantly only at the higher compost rate of 30 Mg ha−1, while EC increased in all the organic matter treatments. Available P significantly increased in the CM1 and CM3 treatments by 55.1 and 86.4 %. The amounts of SOC stock increased by 67.2, 21.4, and 8.6 %, and soil TN stock by 64.1, 20.2, and 8.5 % in CM3, RS, and CM1, respectively, compared to NPK treatment. Significant changes in soil properties were observed after 31 years of organic matter applications with reference to PK- and NPK-fertilized rice paddy soils. A significant decrease in pH was observed with the application of a high rate (30 Mg ha−1) of rice straw compost but not with the conventional rate of 10 Mg ha−1. However, EC increased significantly relative to that of the PK- and NPK-fertilized plots in all the organic matter treatments. Available P significantly increased in the CM1 and CM3 treatments by 55.1 and 86.4 %. The amounts of SOC stock expressed as a percentage of total C applied to the soil were higher from 10 Mg ha−1 compost (28.7 %) than that from 6 Mg ha−1 rice straw (17.4 %), indicating a more effective soil organic C accumulation from rice straw compost than that from original rice straw.

Changes in the soil C and N contents, C decomposition and N mineralization potentials in a rice paddy after long-term application of inorganic fertilizers and organic matter

ABSTRACTA long-term experiment on combined inorganic fertilizers and organic matter in paddy rice (Oryza sativa L.) cultivation began in May 1982 in Yamagata, northeastern Japan. In 2012, after the 31st harvest, soil samples were collected from five fertilizer treatments [(1) PK, (2) NPK, (3) NPK + 6 Mg ha−1 rice straw (RS), (4) NPK + 10 Mg ha−1 rice straw compost (CM1), and (5) NPK + 30 Mg ha−1 rice straw compost (CM3)], at five soil depths (0–5, 5–10, 10–15, 15–20 and 20–25 cm), to assess the changes in soil organic carbon (SOC) content and carbon (C) decomposition potential, total nitrogen (TN) content and nitrogen (N) mineralization potential resulting from long-term organic matter addition. The C decomposition potential was assessed based on the methane (CH4) and carbon dioxide (CO2) produced, while the N mineralization potential was determined from the potassium chloride (KCl)-extractable ammonium-nitrogen (NH4+-N), after 2, 4, 6 and 8 weeks of anaerobic incubation at 30°C in the laboratory. Compared to NPK treatment, SOC in the total 0–25 cm layer increased by 67.3, 21.0 and10.8%, and TN increased by 64.2, 19.7 and 10.6%, in CM3, RS and CM1, respectively, and SOC and TN showed a slight reduction in the PK treatment by 5.2 and 5.7%, respectively. Applying rice straw compost (10 Mg ha−1) instead of rice straw (6 Mg ha−1) to rice paddies reduced methane production by about 19% after the soils were measured under 8 weeks of anaerobic incubation at 30°C. Soil carbon decomposition potential (Co) and nitrogen mineralization potential (No) were highly correlated with the SOC and TN contents. The mean ratio of Co/No was 4.49, lower than the mean ratio of SOC/TN (13.49) for all treatments, which indicated that the easily decomposed organic matter was from soil microbial biomass and soil proteins.

Maize straw effects on soil aggregation and other properties in arid land

Soil structure has been destroyed due to long-term application of inorganic fertilizer in the Loess Plateau of China. Our objective was to determine how incorporation of three different rates of maize (Zea mays L.) straw affected soil aggregate size and stability within the top 30cm of arid soil on the Loess Plateau of China to provide basic theory of land utilization. Three rates of maize straw (4.5, 9.0, or 13.5Mgha−1, hereafter referred to as LS, MS, and HS) were incorporated with 255 and 90kg/ha of inorganic N and P fertilizer, respectively, 2 times in a 4-year field experiment. Water stability of five aggregate size classes (>5, 2–5, 1–2, 0.5–1, and 0.25–0.5mm) in the 0–10, 10–20, and 20–30cm depth increments was measured 3 times for each treatment and a check (CK) that received only the inorganic fertilizers. Incorporation of 13.5Mgha−1 of straw significantly increased water stability of three aggregate classes (>5, 1–2, 0.5–1mm) compared with CK and LS treatments within the surface 10cm and for aggregates >0.5mm in the 10–20cm depth increment. Within the 20–30cm depth increment water-stablity of aggregates in the 0.25–0.5mm class increased significantly as the rate of straw incorporation increased. Overall, aggregate stability was primarily increased through changes in microaggregate size distribution, especially for aggregate classes >5, 0.5–1, 0.25–0.5mm within the 0–10, 10–20, 20–30cm soil depth, respectively. Straw incorporation is a positive and effective agriculture measure to improve soil structure.

Measuring and estimating sulfur mineralization potential in soils amended with poultry litter or inorganic fertilizer

The effect of long-term (more than 10 years) application of poultry litter (PL) or inorganic fertilizer (IF) on sulfur (S) mineralization potential (So) was evaluated using four different soils (Delaware 1, Delaware 2, Iowa, and Georgia). Also, different methods to estimate S availability (extraction with KCl, NaHCO3, and KCl after a wetting-drying cycle, aerobic incubations for 7 and 14 days, and NH4+ quantification after an anaerobic incubation) were compared to So. When compared to long-term application of IF, long-term application of PL generated an increase in total soil S ranging from 0 to 0.14 g kg−1, which was positively associated with the soil clay content (R2 = 0.98), and resulted in an increase in So ranging from 0 to 21.2 g kg−1. From the evaluated methods to estimate So, only three of them were significantly (p < 0.05) correlated to So: aerobic incubation for 7 days (r = 0.85), extraction with NaHCO3 (r = 0.85), and nitrogen anaerobic incubation (r = 0.99). Based on the reduced time and labor involved and in their capacity to distinguish between treatments, we recommend further use and further evaluation of the last two methods as estimators of So.

Long-term impacts of manure, straw, and fertilizer on amino sugars in a silty clay loam soil under temperate conditions

There is increasing evidence that microorganisms participate in soil C sequestration and stabilization in the form of resistant microbial residues. The type of fertilizers influences microbial activity and community composition; however, little is known about its effect on the microbial residues and their relative contribution to soil C storage. The aim of this study was to investigate the long-term impact (21 years) of different fertilizer treatments (chemical fertilizer, crop straw, and organic manure) on microbial residues in a silty clay loam soil (Udolls, USDA Soil Taxonomy). Amino sugars were used to indicate the presence and origin of microbial residues. The five treatments were: CK, unfertilized control; NPK, chemical fertilizer NPK; NPKS1, NPK plus crop straw; NPKS2, NPK plus double amounts of straw; and NPKM, NPK plus pig manure. Long-term application of inorganic fertilizers and organic amendments increased the total amino sugar concentrations (4.4–8.4 %) as compared with the control; and this effect was more evident in the plots that continuously received pig manure (P < 0.05). The increase in total amino sugar stock was less pronounced in the straw-treated plots than the NPKM. These results indicate that the accumulation of soil amino sugars is largely influenced by the type of organic fertilizers entering the soil. Individual amino sugar enrichment in soil organic carbon was differentially influenced by the various fertilizer treatments, with a preferential accumulation of bacterial-derived amino sugars compared with fungal-derived glucosamine in manured soil.