Long-term Tillage Effects Research Articles

Long-Term Effects of Nitrogen and Tillage on Yields and Nitrogen Use Efficiency in Irrigated Corn

By tonnage, corn (Zea mays L.) is the #1 crop produced globally, and recent research has suggested that no-till (NT) systems can lead to reduced yields of this important crop. Additionally, there is a lack of long-term data about the effects of tillage and N management on cropping systems. Corn is the most nitrogen (N)-fertilized crop in the USA, and N losses to the environment contribute to significant impacts on air and water quality. We conducted long-term studies on conventional tillage (CT) and conservation tillage systems, such as strip tillage (ST) and NT, under different N rates. We found that immediately after conversion to NT, yields from NT were significantly lower than yields from CT (p < 0.1), but after five years of NT, the NT yields were 1.5% higher than the CT yields (p < 0.1). Initially, the NT yields were lower than the ST (p < 0.01), but after seven years of NT, the NT yields were comparable to ST grain yields. Although the total aboveground N uptake with NT immediately after conversion to NT was lower than with CT and ST, these differences were not significant in the long run. The nitrogen use efficiency (NUE) with NT increased over time. The present work highlights the importance of long-term research for determining the cumulative impacts of best management practices such as NT. We found that NT becomes a more viable practice after five or seven years of implementation, demonstrating the high importance of long-term research.

Effect of Long Term Tillage and Soil Moisture Regime on the Chemical Properties of Soil under Mung Bean-Wheat and Sorghum-Wheat Cropping System

Effect of Long Term Tillage and Soil Moisture Regime on the Chemical Properties of Soil under Mung Bean-Wheat and Sorghum-Wheat Cropping System

No tillage and leguminous cover crop improve soil quality in a typical rainfed Mediterranean system

Soil and crop management influence soil organic carbon (SOC), chemical composition, and overall soil quality. In a Mediterranean region, a study initiated in 1994 examined the long-term effects of conventional tillage (CT) versus no-tillage (NT) practices. Initially focusing on continuous durum wheat cultivation until 2009, the experiment later introduced a 2-year rotation of durum wheat and Vicia faba L. cover crops in half of the CT and NT fields. SOC was monitored from 2008 to 2018, while microbial biomass (as dsDNA), soluble nitrogen (N), and enzyme activities (EAs) were monitored from 2011 to 2014 to evaluate the rotation’s impact. Between 2009 and 2018, CT yields were on average 15% higher than NT, especially during high rainfall years. NT significantly increased SOC content in the 0–30 cm soil layer, along with higher levels of soluble N, dsDNA, and EAs at 0–10 cm depth. NT led to a 23% and 10% increase in SOC stock and SOC stock per equivalent soil mass compared to CT. EAs increased by over 50% under NT, indicating enhanced biological activity. The SOC increase due to NT was limited to the top 10 cm, with a decrease at deeper depths (up to 50 cm). Introducing cover crops over 4 years did not yield significant impacts, suggesting the need for a longer period to observe noticeable effects. Overall, adopting NT practices resulted in higher SOC concentration, enhanced soil biological activity, and improved biogeochemical cycles, emphasizing the positive impact of NT on soil health and sustainability.

Effects of Long-term Tillage on Soil Bacterial Community Structure and Physicochemical Properties of Dryland Wheat Fields in Northern China

To explore the effects of long-term tillage on bacterial community structure in different soil layers of dryland wheat fields and its relationship with soil physicochemical properties, a long-term field experiment was conducted from 2016 to 2021 in Wenxi Experimental Demonstration Base of Shanxi Agricultural University, Shanxi Province. We studied the effects of no-tillage (NT), subsoiling-tillage (ST), and deep plowing (DP) on soil physicochemical properties; α and β diversity of the bacterial community; and dominant and different species of phyla and genera in different soil layers. Additionally, PICRUSt2 was used to predict the metabolic function of soil bacterial community. The results revealed that subsoiling-tillage and deep plowing significantly increased the soil water content in the 20-40 cm soil layer and significantly decreased the soil organic carbon content in the 0-20 cm soil layer compared with that under no-tillage for five consecutive years. Compared with that under deep plowing, subsoiling-tillage significantly increased soil water content, soil organic carbon content, dissolved organic carbon content, and dissolved organic nitrogen content in the 0-20 cm soil layer. Compared with that under no-tillage, subsoiling-tillage and deep plowing increased the α diversity of the soil bacterial community in the 0-40 cm soil layer, and subsoiling-tillage was higher than deep plowing. Compared with that under no-tillage, subsoiling-tillage and deep plowing significantly increased the relative abundances of Acidobacteria and Nitrospirae in the 0-20 cm soil layer and Acidobacteria, Chloroflexi, Gemmatimonadetes, Rokubacteria, GAL15, and Nitrospirae in the 20-40 cm soil layer. Compared with that under no-tillage, subsoiling-tillage and deep plowing significantly increased the relative abundance of Nitrospira in the 0-20 cm soil layer and Rubrobacter and Streptomyces in the 20-40 cm soil layer. Compared with that under deep plowing, subsoiling-tillage significantly increased the relative abundance of Acidobacteria and Gemmatimonadetes in the 0-40 cm soil layer. Redundancy analysis demonstrated that the contents of soil organic carbon, dissolved organic carbon, and dissolved organic nitrogen in the 0-20 cm soil layer exerted positive effects on Actinobacteria and Blastococcus, and the soil water content in the 0-40 cm soil layer exerted positive effects on Acidobacteria, Chloroflexi, and Gemmatimonadetes under subsoiling-tillage. The results of PICRUSt2 prediction showed that subsoiling-tillage and deep plowing significantly increased the relative abundance of amino acid metabolism and the metabolism of cofactors and vitamins but decreased the relative abundance of lipid metabolism of bacterial communities in the 20-40 cm soil layer compared with that under no-tillage. Compared with that under deep plowing, subsoiling-tillage significantly increased the relative abundances of amino acid metabolism in the 0-40 cm soil layer and other amino acid metabolism in the 0-20 cm soil layer. In conclusion, subsoiling-tillage or deep plowing could increase the soil water content, α diversity of the soil bacterial community, and their metabolic capacity in the dryland wheat fields during the summer fallow period. The relative abundance of Acidobacteria and Gemmatimonadetes and the ability of amino acid metabolism of the bacterial community were increased by subsoiling-tillage, and thus the contents of soil dissolved organic carbon and dissolved nitrogen can be increased.

Soil Aggregation and Associated Organic Carbon and Total Nitrogen in a Sandy Loam Soil under Long-Term Tillage Effects

In Tunisia, climate change impacts that lead to the degradation of soil resources are considered to be a major limiting factor on socio-economic development. These impacts are exacerbated by the intensive plowing and cultivation practices used by Tunisian farmers, which expedite the depletion of soil organic matter (SOM), leading to changes in the physio-chemical properties of soil and consequently promoting soil erosion. In fact, the decrease in soil organic carbon (SOC) stocks affects soil’s fertility and the ability to regulate climate change. The objective of this study, which was conducted in Le Krib in the Siliana region of northwestern Tunisia, was to evaluate the effects of two cropping systems, consisting of durum wheat (Triticum aestivum) and oats (Avena sativa), and two types of tillage, no-till (NT) and mouldboard plowing (MP), on different soil aggregate classes (>2000 µm, 2000–250 µm, 250–180 µm, 180–53 µm and <53 µm) and soil physio-chemical properties, as well as the resulting effects on the carbon and nitrogen concentrations in these aggregates. The results showed that the carbon content of all soil aggregate classes was influenced by interactions between the previous crop and tillage regime. The clay-silt fraction had higher carbon concentrations under no-till and mouldboard plowing management. Furthermore, the previous crop and tillage type and their interactions had significant effects on nitrogen concentrations in micro-aggregates. The highest nitrogen concentrations (2846.6 ppm) were found in micro-aggregates in soils where the previous crop was durum wheat and mouldboard plowing was used, while the lowest concentrations (1297 ppm) were obtained in soils where the previous crop was oats and mouldboard plowing was used.

Combined effects of long-term tillage and fertilisation regimes on soil organic carbon, microbial biomass, and abundance of the total microbial communities and N-functional guilds

Reduced tillage intensity is known to increase soil organic carbon (SOC) in the topsoil, but can also lead to increased microbially derived nitrous oxide (N2O) emissions. Although the trade-offs between C sequestration and N2O emissions under different agricultural practices have been extensively investigated, the reported results are conflicting and, thus remain unclear. In this study, the effects of different types of tillage [no-till (NT) and conventional mouldboard tillage (CT)] in combination with four fertilisation regimes [unfertilised control (CON), mineral NPK (MIN), organic (compost) (ORG), and mixed (NPK + compost) (MIX)] on SOC and microbial biomass (Cmic) were examined two decades after the experiment was initiated. The abundance of the microbial community and N-functional guilds within the soil profile (up to a depth of 60 cm) was also determined. SOC content was significantly higher in NT than in CT at 0–10 cm depth, with an average difference of 0.6–1.3 % SOC, depending on fertilisation. Organic fertilisation increased the SOC content in both tillage systems up to a depth of 20 cm. Microbial biomass, abundance of total bacterial and archaeal 16S rRNA, and fungal ITS genes decreased with depth, corresponding to the decrease in SOC, and, consequently, were higher in NT than in CT, in the top 20 cm soil for microbial biomass and bacterial abundance and top 10 cm for fungi and archaea. Denitrifiers and ammonium oxidising archaea (AOA) were affected by soil depth and tillage, whereas the distribution of ammonium oxidising bacteria (AOB) was affected by fertilisation and depth. The ratios between (i) the two nitrite-reducing communities (nirS/nirK), (ii) the two N2O-reducing communities (nosZI/nosZII), and (iii) the nitrite- and N2O-reducing communities [(nirK + nirS)/(nosZ + nosZII)] increased significantly with soil depth, indicating niche differentiation caused by differences in nutrients contents and environmental conditions. Overall, stratification of SOC and nutrients in the soil by tillage and fertilisation was the main driver of the differences in the total microbial and N cycling communities. The findings of our study provide novel insights that can aid in development of effective strategies for steering soil microbiome responsible for N2O emissions.

Rotational Tillage: A Sustainable Management Technique for Wheat Production in the Semiarid Loess Plateau

Rotational tillage could be an advisable attempt to overcome some of the adverse impacts of mono conservation tillage, and it is necessary to assess the feasibility of adoption of rotational tillage for sustaining productivity in the long run. Data from an 8-year site-specific field study conducted on the Loess Plateau were used to estimate the long-term effect of rotational tillage on soil water dynamic, soil properties and winter wheat (Triticum aestivum L.) productivity. Three mono-tillage (No tilling (NT), subsoiling (ST) and ploughing (PT)) and three rotational tillage (NT/ST (NT and ST performed alternately), ST/PT, PT/NT) methods were applied after wheat harvest. Results showed the mean grain weight in the three rotational tillage treatments was 4.5% to 16.9% greater than in NT, and water use efficiency (WUE) was 5.0% to 18.8% greater over the 8 years. Rotational tillage could overcome the increased bulk density and nutrition stratification caused by NT and soil degradation due to PT. NT/ST was the best rotational tillage pattern with the highest grain yield and WUE, best soil property and relatively low mechanical cost in the present study. Here, we demonstrate that rotational tillage can improve wheat yield, WUE and soil properties compared with long-term no tilling and recommend using NT/ST as the optimal tillage pattern in similar ecological regions.

Long Term Effects of Tillage–Crop Rotation Interaction on Soil Organic Carbon Pools and Microbial Activity on Wheat-Based System in Mediterranean Semi-Arid Region

Conservation agriculture based on no-tillage (NT) and crop rotation allows to enhance soil health. Based on data collected from long-term trials in a semi-arid region of Tunisia, results showed that NT increased significantly soil organic carbon stock (SOCS), soil microbial biomass carbon (SMBC), arbuscular mycorrhizal fungal (AMF) root colonization, and soil microbial respiration (CO2) at 0–20 cm topsoil layer compared to conventional tillage (CT). Moreover, triennial rotation (TRI), based on annual succession of Faba bean-Durum wheat-Barley, and biennial rotation (BI), based on annual succession of Faba bean-Durum wheat, increased significatively SMBC, AMF, and CO2. Likewise, a significant benefit of the two-way interactions Tillage × Rotation was observed. Furthermore, NT combined with TRI recorded the highest SOCS (2181 g C m−2), SMBC (515 mg C kg−1 soil), AMF (14%), and CO2 which is an indicator of soil microbial respiration (1071 mg CO2 kg−1 soil). The current results highlight the benefit adoption of minimum or (NT)combined with crop diversification on soil health.

Soil organic matter fractions in an Oxisol under tillage systems and winter cover crops for 26 years in the Brazilian subtropics

The improvement of carbon (C) accumulation in soils has been one of the main purposes of the conservation systems in agricultural production. This study aimed to assess the long-term effect of conventional tillage (CT) and no-tillage (NT) combined with winter cover crops, black oat and oilseed radish, and fallow on C accumulation and stabilization in a very clayey Oxisol in Southern Brazil. Soil samples were collected in the 0-0.05, 0.05-0.10 and 0.10-0.20 m layers of a 26-year-old experiment. Distribution of size-class aggregates, C stock in aggregates, total C stock, and C stocks in the physical fractions, free particulate organic matter (free-POM), occluded particulate organic matter (occluded-POM) and mineral-associated organic matter (min-OM) were assessed. NT had a higher percentage of macroaggregates and C stock in this size-class, and also higher C stock in bulk soil, free-POM and occluded-POM fractions than CT in 0-0.05 m (Tukey’s test p < 0.05), due to higher input of biomass and minimum soil mobilization in NT. Oat and radish had higher C stock in macroaggregates than fallow in 0.05-0.10 m (Tukey’s test p < 0.05). Radish had the highest C stock in the free-POM (0-0.05 m). Fallow decreased the stabilization of macroaggregates and C accumulation in free-POM, due to the lower C input from aboveground biomass over the years. In conclusion, NT after 26 years improved C accumulation and stabilization, mainly in the superficial layer and in POM fractions, and winter cover crops favored the formation and stability of macroaggregates.

Effect of long-term tillage and cropping system on portion of fungal and bacterial necromass carbon in soil organic carbon

The microbial necromass carbon (M-C) is considered to be relatively stable and important part of SOC. However, knowledge about the contribution of M-C storage in increasing SOC storage and the influences of tillage and cropping systems on fungal and bacterial necromass carbon (F-C and B-C) is lacking, especially in the long-term. Here, a subset of treatments in a long-term 16-year study was used to evaluate these changes. The treatments selected for present study were: (1) NTCS: no-tillage with two year corn-soybean (CS) rotation (Zea mays L. – Glycine max Merr.); (2) MPCS: moldboard plowing with two year corn-soybean rotation; (3) NTCC: no-tillage with continuous corn (CC); (4) MPCC: moldboard plowing with continuous corn; (5) CTCC: conventional tillage with continuous corn and no residue return (traditional tillage practice in China). Amino sugars were measured to calculate the M-C, F-C and B-C and their storage. Three-way ANOVA showed that tillage, depth and their interactions had significant effect on all amino sugars. However, two-way ANOVA in separate layers showed the effects of tillage on all amino sugars mostly occurred in 0–5 cm layer. A decaying exponential model showed the relationship between the M-C and SOC (R2 = 0.87). Tillage showed great effects on the amount of M-C, F-C and B-C storage but had no influence on the proportion of their distribution in SOC storage (%). More than half of the increase in SOC storage existed as M-C storage under CC cropping due to returned residue, which was higher than CS. F-C storage % was not affected by agriculture management (residue return, tillage and cropping), whereas B-C storage % was affected by both quantity and quality of residue. The results suggested that CC cropping system was better for M-C sequestration and that bacteria were relatively more sensitive to agriculture management than fungi.

Long-term fertilization and tillage regimes have limited effects on structuring bacterial and denitrifier communities in a sandy loam UK soil.

Denitrification causes loss of available nitrogen from soil systems, thereby reducing crop productivity and increasing reliance on agrochemicals. The dynamics of denitrification and denitrifying communities are thought to be altered by land management practices, which affect the physicochemical properties of the soil. In this study, we look at the effects of long-term tillage and fertilization regimes on arable soils following 16 years of treatment in a factorial field trial. By studying the bacterial community composition based on 16S rRNA amplicons, absolute bacterial abundance and diversity of denitrification functional genes (nirK, nirS and nosZ), under conditions of minimum/conventional tillage and organic/synthetic mineral fertilizer, we tested how specific land management histories affect the diversity and distribution of both bacteria and denitrification genes. Bacterial and denitrifier communities were largely unaffected by land management history and clustered predominantly by spatial location, indicating that the variability in bacterial community composition in these arable soils is governed by innate environmental differences and Euclidean distance rather than agricultural management intervention.

Long-term effects of tillage and nitrogen fertilization on soil C and N fractions in a corn–soybean rotation

Tillage and nitrogen (N) fertilization can influence soil organic matter (SOM) dynamics, but their interactive effects remain contradictory. A long-term (25 yr) corn (Zea mays L.)-soybean (Glycine max L. Merr.) rotation was used to investigate the effect of tillage [moldboard plow (MP) and no-till (NT)] and N rates (0, 80, and 160 kg N·ha−1) on soil organic carbon (SOC), total N (STN), respiration, and SOM fractions [particulate organic matter (POMC, POMN), mineral-associated organic matter (MAOMC, MAOMN), and microbial biomass (MBC, MBN)]. Results indicate that NT had 27% higher SOC and 24% higher STN than MP in the 0–20 cm depth. Furthermore, SOC and STN stocks (0–20 cm) were 22% and 20% higher, respectively, under NT than MP. There was significant stratification under NT, with a rather uniform distribution under MP. The SOM fractions and soil respiration were 28%–275% and 20%–83% higher at the 0–5 and 5–10 cm depths, respectively, under NT than MP. Interestingly, N fertilizer rate or its interaction with tillage had no impact, except for respiration (tillage × N rate and N rate × depth). Hence, while N addition was required for adequate grain production and increased cumulative plant C and N inputs, our findings indicate that the vertical distribution of SOC, STN, and SOM fractions was affected by tillage, thereby influencing resource accessibility and subsequent dynamics of SOM fractions. Taken together, our results support the adoption of NT and judicious use of N fertilizers for enhancing topsoil SOM storage and fertility under humid temperate conditions.

Long term effects of tillage and fertilization upon microbiota of a Romanian Chernozem under maize monoculture

The effects of agricultural practices upon soil microbiota were assessed in case of a long-term (42 years) tillage and fertilization experiment run on Chernozem soil under maize monoculture, as well as by comparing the experimental field with a grassland located nearby. We measured overall microbial biomass carbon (Cmic) as an indicator for total community size and ergosterol as a proxy for saprotrophic fungal biomass. We interpreted ergosterol: Cmic ratio as an indicator for community structure. Our findings showed that no till is characterized by a significantly increase in Cmic compared to chisel and mouldboard plough (+31% and + 16%, respectively). We further found that Cmic of the grassland was more than double the microbial biomass of experimental plots. Ergosterol concentration manifested the same tendency as overall microbial biomass across tillage treatments, however the impact was statistically significant only between zero tillage and chisel plough (+51%). Although ergosterol to Cmic ratio was higher in case of no till (+6% and + 17% compared to conventional tillage and chisel plough, respectively), the impact was not statistically significant. Similarly, moderate nitrogen fertilization (60 kg/ha) induced no significant effect whatsoever, a consequence that is attributed to the rather low dose applied.

The lagging movement of soil nitrate in comparison to that of soil water in the 500-cm soil profile

The combination of forage-crop rotation with conservation tillage has long been known to result in proven productivity and sustainability, but less information is available on the influence of long-term conservation tillage practices on the movement of soil water and residual nitrate at deep soil depths in forage-crop rotation systems. In this study, we measured the changes in soil water storage, residual soil nitrate accumulation and their relationship to study the long-term effects of tillage and mulching practices on regional nitrogen management in maize (Zea mays L.)-wheat (Triticum aestivum L.)-common vetch (Vicia sativa L., annual legume forage) rotation system. Soils were collected from the 500-cm soil profile at the harvest stage of the maize and common vetch after 19 years of continuous conventional tillage (T), conventional tillage followed by straw mulching (TS), no tillage (NT), and no tillage followed by straw mulching (NTS) on the Loess Plateau, China. The results showed that the NT practices increased soil water storage by 3.07% compared with the T practices in the maize field, mulching practices increased soil water storage by 3.47% compared with no mulching practices in the common vetch field, and the improvement effect was mainly concentrated in the deep soil layer (150–500 cm). When compared with no mulching, straw mulching practices increased residual soil nitrate accumulation by 51.20 kg ha−1 at shallow soil depths (0–120 cm) but decreased this accumulation by 206.09 kg ha−1 at deep soil depths (120–500 cm) in the maize field; however, straw mulching decreased nitrate accumulation by 16.25 kg ha−1 throughout the whole profile (0–500 cm) in the common vetch field. The NT practices decreased residual soil nitrate accumulation by 131.65 kg ha−1 compared with the T practices in the maize field but had no effects on the common vetch field in the 0–500-cm soil profile. Greater changes in soil residual nitrate accumulation appeared at depths of 200–500 cm than at other depths. Moreover, according to structural equation model, nitrite accumulation was limited by soil water storage. Soil nitrate peaked at deeper soil depths in the NT (90–120 cm) and TS (250–300 cm) treatments than in the T treatment (60–90 cm), whereas the NTS treatment resulted in no nitrate accumulation peak across the whole soil profile. Soil water recharge and depletion were deeper in the NT and TS treatments than in the T treatment, and this effect could limit the further leaching of soil nitrate into deep soil. The depth of soil water recharge was deeper than the depth of nitrate accumulation, and the vertical movement speed of soil residual nitrate was slower than that of soil water. Therefore, the downward movement of soil nitrate lagged behind that of soil water. Together, these results demonstrated that the NTS treatment exerted the strongest effect on maintaining soil water and decreasing residual nitrate accumulation at deep soil depths, which will be favorable for improving regional N management and assessing N budgets in agroecological systems on the Loess Plateau.

Long-term combined effects of tillage and rice cultivation with phosphogypsum or farmyard manure on the concentration of salts, minerals, and heavy metals of saline-sodic paddy fields in Northeast China

Soil sodicity is a major ecological problem in the western Songnen Plain of Northeast China and rice cultivation is the main approach used to mitigate saline-sodic soils. However, rice cultivation alone may not be the most effective practice. This study aimed to investigate the combined effects of annual tillage and rice cultivation with either phosphogypsum or farmyard manure on soil salinity, mineral status, and concentration of heavy metals in saline-sodic paddy fields. Treatments were: 1) untreated (no amendments), untilled, and uncultivated (no rice) saline-sodic native grasslands (UG); 2) untreated, tilled, rice-cultivated paddy fields (PFU); 3) tilled, rice-cultivated, amended paddy fields with phosphogypsum (PFPG); and 4) tilled, rice-cultivated, amended paddy fields with farmyard manure (PFFM). The effectiveness of these treatments on soil improvement was evaluated after a 10-year field experiment. Compared to the UG control, the 0–20 cm topsoil layer of PFU, PFPG, and PFFM had respective decreases in Na+ concentrations of 42.9%, 61.5%, and 60.9%; in CO32- + HCO3- concentrations of 18.9%, 63.2%, and 57.9%; in Cl- concentration of 64.6%, 75.7%, and 79.9%; in pH units of 0.57, 1.05, and 1.30; in soil electrical conductivity (EC1:5) of 18.3%, 49.1%, and 48.3%; and in exchange sodium percentage (ESP) of 47.2%, 66.9%, and 72.5%. Also, the 0–20 cm topsoil layer of PFPG and PFFM had its concentrations of soil organic matter (SOM), available nitrogen (AN), and available phosphorus (AP) significantly (P < 0.05) increased compared to the UG control. However, the concentrations of five heavy metals (As, Pb, Cd, Cr, and Hg) were kept within a safe range in saline-sodic paddy fields amended with phosphogypsum or farmyard manure and were far below the environmental quality standard held for Chinese soils. Therefore, phosphogypsum and farmyard manure significantly decreased soil salinity and sodicity while increased soil fertility and SOM. Because these amendments are locally available and affordable to farmers, their use is deemed suitable for large-scale soil reclamation and the mitigation of salinity and sodicity in soils destined for rice cultivation in Northeast China.

Effect of long-term Tillage and Nitrogen Fertilization Residue on Soil Biochemical Properties and Crop Yield

Sustainable soil management practices are necessary to enhance or maintain soil quality and crop yields. The objective of this experiment was to study the effect of long-term (32 years) tillage system and nitrogen fertilization residue on soil bacteria and fungi, growth and production of cowpea (Vigna unguiculata). This research was conducted using factorial experiment, arranged in a randomized block design with four replications. The first factor was tillage systems consisted of Intensive Tillage (T1) and No tillage(T2),the second factor was nitrogen fertilization residue (N) consisted of N1 (0 kg N ha-1) and N2 (200 kg N ha-1). Data were analyzed using analysis of variance, if there is a significant difference will be continued with Least Significant Difference (BNT) test at 5%. Soil bacteria and fungi data were used to figure out the Diversity Index (H'), Dominance Index (D) and the Evenness Index (e). Principal Component Anaysis (PCA) used to determined the relationship among observed variabels. The results showed that T2 could give better results on soil respiration, bacteria and fungi population than T1. Lower soil pH found at N2 compared to N1. Long term N1T2 was able to support cowpea growth and yield as high as N2T1. Principal component analysis showed that there was an interrelationship among soil biochemical properties, growth and yield of cowpea.

Long-term effects of crop rotation, tillage, and fertilizer nitrogen on soil health indicators and crop productivity in a temperate climate

Although diversifying crop rotations with perennials and cover crops and implementing no-tillage practices has been promoted as an effective strategy for increasing soil carbon and nitrogen storage in the long-term, uncertainty still remains, particularly regarding the association between crop productivity and soil health. Therefore, using two long-term experiments, we investigated the effects of crop rotation, tillage system, and nitrogen fertilizer application (at Ridgetown only) on surface soil (0−15 cm depth) parameters (soil organic carbon (SOC), total nitrogen (TN), commercial soil health tests (evolved CO2 and NH3 indicating microbial activity)), and crop yield in 2016. We used 5-yr average crop yield variability to test for the relationship of SOC and TN with crop yield stability. Results indicated that diversification of corn and soybean rotations and their monocultures with cover crops, perennials, and small grain cereals enhanced soil health indicators (by 32% at Ridgetown (21 yr) and 49% at Elora (36 yr)) and crop productivity (16% at Ridgetown and 29% at Elora). At Ridgetown, corn yield was 10.4% greater with including red clover to the corn-soybean-winter wheat than monoculture corn. Similarly, corn yield was enhanced by 25% when alfalfa was added to monoculture corn at Elora. Nitrogen fertilizer application did not increase surface SOC storage at Ridgetown. No-tillage system had greater evolved NH3-N (by 7.2%) and evolved CO2-C (by 27.9%) than conventional tillage at Elora only. Consistent with management effects on crop yield, at both sites, evolved NH3-N and CO2-C were greatest from rotations with winter wheat, red clover, and alfalfa. Additionally, a strong positive relationship of SOC and TN with soil health tests confirms the suitability of the commercial tests to detect management effects on soil health indicators in the long-term. At both sites, SOC positively correlated with crop yield indicating a direct association between soil carbon status and agroecosystem resiliency. We conclude that diversifying crop rotations increases soil microbial activity, surface SOC sequestration, and crop productivity in the long-term; thus, is a critical component for developing sustainable agroecosystems.

Soil Microbial Indicators within Rotations and Tillage Systems.

Recent advancements in agricultural metagenomics allow for characterizing microbial indicators of soil health brought on by changes in management decisions, which ultimately affect the soil environment. Field-scale studies investigating the microbial taxa from agricultural experiments are sparse, with none investigating the long-term effect of crop rotation and tillage on microbial indicator species. Therefore, our goal was to determine the effect of rotations (continuous corn, CCC; continuous soybean, SSS; and each phase of a corn-soybean rotation, Cs and Sc) and tillage (no-till, NT; and chisel tillage, T) on the soil microbial community composition following 20 years of management. We found that crop rotation and tillage influence the soil environment by altering key soil properties, such as pH and soil organic matter (SOM). Monoculture corn lowered pH compared to SSS (5.9 vs. 6.9, respectively) but increased SOM (5.4% vs. 4.6%, respectively). Bacterial indicator microbes were categorized into two groups: SOM dependent and acidophile vs. N adverse and neutrophile. Fungi preferred the CCC rotation, characterized by low pH. Archaeal indicators were mainly ammonia oxidizers with species occupying niches at contrasting pHs. Numerous indicator microbes are involved with N cycling due to the fertilizer-rich environment, prone to aquatic or gaseous losses.

Conservation tillage increases corn and soybean water productivity across the Ohio River Basin

Optimizing agricultural management practices is imperative for ensuring food security and building climate-resilient agriculture. The past several decades have witnessed the emergence of conservation tillage practices to combat soil erosion and degradation. However, the effects of conservation tillage on crop water productivity (CWP) remain uncertain, especially from a regional-scale perspective. Here, we used an improved process-based agroecosystem model (DLEM-Ag) to quantify the long-term effects of conservation tillage (e.g., no-tillage, NT; reduced tillage, RT) on CWP (defined as the ratio of crop productivity to evapotranspiration) of corn and soybean across the Ohio River Basin during 1979–2018. Our results revealed an average increase of 2.8% and 8.4% in CWP for corn and soybean, respectively, under the NT adoption scenario. Compared to the conventional tillage scenario, NT and RT would enhance CWP, primarily due to reductions in evapotranspiration, particularly evaporation. Further analysis suggested that, although NT and RT may decrease surface runoff, these practices could also increase subsurface drainage and nutrient loss from corn and soybean farmland via leaching. These results indicate that conservation tillage should be complemented with additional water and nutrient management practices to enhance soil water retention and optimize nutrient use in the region's cropland. Our findings also provide unique insights into optimizing management practices for other areas where conservation tillage is widely applied.

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