Biannual Rotation Research Articles

Durum Wheat Production and Soil Chemical Properties in Response to Three Biannual Rotation Cycles with Residue Incorporation

Crop rotations incorporating residues generates benefits in productivity and a better efficiency of resources. However, the incorporation of residues in high quantities is not a common practice, given the lack of comprehension of farmers of the effects on the following crop. This experiment was carried out in an Andisol soil in south-central of Chile. Three biannual rotation cycles (canola-durum wheat and bean-durum wheat) with four levels of residue incorporation (0%, 50%, 100% and 200%) were evaluated on the evolution of grain yield and production of durum wheat residues, and on chemical properties of the soil at the end of the three cycles. The results indicated that pre-cultivation affected the grain yield and residue production of durum wheat, highlighting the positive effect of the bean. In soil, a higher concentration of available N and exchangeable Ca, Mg and K was obtained in the bean-durum wheat rotation, and a higher concentration of available S in the canola- durum wheat rotation. By increasing the dose of waste, an increase in the concentrations of exchangeable Ca, Mg and K was achieved. Finally, the chemical properties of the soil presented positive and negative correlations associated with the management of liming, fertilization and nutrients mostly present in the incorporated waste. This study helped to validate that the continuous incorporation of the residues produced within the rotations in this volcanic soil contributes to the improvement of some of its chemical properties with no effect of yield of the durum wheat crop.

Three Biannual Rotations Cycles with Residue Incorporation Affect Wheat Production and Chemical Soil Properties.

There are few reports of crop rotations with high residue incorporation in terms of their effects on indicator crop yields and soil properties, so this study evaluated the effect of two medium-term biannual rotations on wheat yield development and soil chemical properties after six years of rotation. The experiment was conducted with two biannual rotations (canola-wheat and bean-wheat) and four residue incorporation levels (0%, 50%, 100%, and 200%) in an Andisol in south central Chile. Wheat grain yield and residue production were evaluated during each biannual cycle during three cycles of crop rotation, and soil chemical properties were evaluated at final evaluation. The use of beans as a wheat preculture partially improved grain yield in 7.3%. The chemical properties of the soil showed an increase in pH (0.08 units), organic matter content (15 g kg-1), and concentrations of P (2.8 mg kg-1), S (7.4 mg kg-1), and Al (0.03 cmol+ kg-1) after canola cultivation, while after bean cultivation there was an increase in the available N concentration (3.7 mg kg-1). The use of increasing doses of residue allowed for an increase in the soil pH and decrease in the exchangeable Al concentration. The continuous incorporation of the residues produced within the biannual rotations evaluated in this volcanic soil did contribute to improving some chemical properties of the soil without affecting wheat crop yield.

Residue incorporation in biannual rotations of bean-corn and canola-corn affects soil chemical properties and corn yield

Residue incorporation in biannual rotations of bean-corn and canola-corn affects soil chemical properties and corn yield

Effect of three crop rotations and four residue levels on canola and bean grain yield and residue production

AbstractCrop rotation in agriculture can lead to increased crop productivity in the rotation and improved soil fertility as a result of residue incorporation. Unfortunately, residue incorporation is not a common practice in crop production systems under the Mediterranean regime, largely due to the lack of information on the effect of the follow-up crops. Therefore, this study was conducted with six biannual rotations (bread wheat–canola, bread wheat–bean, durum wheat–canola, durum wheat–bean, corn–canola and corn–bean) using four residue incorporation levels (0, 50, 100 and 200%) in an Andisol in south central Chile. Grain yield and residue production were evaluated in the canola and bean crops 5 years after initiating crop rotation. The previous crop affected canola grain yield and residue production, which were both higher after corn. Meanwhile, the residue incorporation level had a slight effect on residue production after bread wheat. Only bean grain yield was affected by the previous crop, which was higher after the durum wheat and corn crops. The residue incorporation has marginally affected residue production after bread wheat. Finally, residue incorporation at different levels under the conditions of the present experiment had a minimal effect on bean and canola residue production following the bread wheat crop. The best crop rotation for canola grain yield was corn–canola, which produced 0.54 Mg/ha (18.3%) higher yield than the average of the other two rotations. The best crop rotation for achieving higher bean grain yield was corn–bean, which yielded 0.52 Mg/ha (12.3%) higher than the average of the other two rotations.

C-sequestration and resilience to climate change of globe artichoke cropping systems depend on crop residues management

Globe artichoke is one of the most intensively cultivated horticultural species in Mediterranean regions. In this context, sustainable agronomic management is a requisite to increase the soil carbon content, making the artichoke cultivation system more resilient to climate change. A 10-year experiment was considered to forecast the influence on soil C dynamic of three globe artichoke managements: monoculture with dry crop residues incorporation (conventional monoculture), monoculture with the inclusion of a cover crop (alternative monoculture), and rotation with cauliflower plus cover crop (biannual rotation). During the 2006–2016 period, total soil organic carbon content and plant C inputs to soil were measured. RothC model was used to predict the effect on the soil C stock and C sequestration potential in 20 years of the three managements tested in the field, plus a hypothetical conventional scenario with no residues’ incorporation (no residues). Plant C inputs increased according to the number of crops in rotation in each system, resulting 25% lower in conventional monoculture with respect to biannual rotation, whereas the C stock change was significantly higher (p < 0.01) in conventional and alternative monoculture (+ 7.57 and 7.14 t C ha-1) compared to biannual rotation (-1.03 t C ha-1). In the 20-year predictions, all the systems had a positive C balance. The soil organic carbon change (t C ha-1) for the future climate was + 7.2 for alternative monoculture and + 0.6 for monoculture with residues removals. For the first time, in this study, we clearly shown in the long term and in a climate change perspective that an improper crop residues management might lead to a loss of soil fertility in intensively cultivated horticultural soils under Mediterranean climate. The adoption of biannual rotation with cauliflower needs to be evaluated carefully because it proved to be less efficient in terms of C sequestration potential.

Canola production and effect on soil chemical properties in response to different residue levels from three biannual crop rotations

ABSTRACT Conservation agriculture using crop rotations and residue management is increasingly accepted in conventional agricultural systems. However, the effects on crop productivity and soil properties of different rotations, levels of use, and residue management have yet to be fully understood. Our study considered the effect of three previous crops (bread wheat, durum wheat, and corn) and four levels of residue incorporation (0%, 50%, 100%, and 200%) in a split plot design with four replicates on canola production parameters and soil chemical properties at the end of this crop. Production parameters and soil chemical properties were mostly affected by the previous crop and less by the residue incorporation rates under the conditions of this experiment; however, neither of these factors affected grain yield (ranging from 4.0 to 4.8 Mg ha−1). Canola residue production was higher (9.7%) after the corn crop, regardless of the residue incorporation rate, but the harvest index was lower after this crop. Most of the soil chemical properties were also affected, revealing increased organic matter and exchangeable K when the previous crop was corn and decreased concentrations of the cations with basic reaction when the previous crop was durum wheat.

Durum wheat grain production, grain quality, and plant nutrient concentration in response to different residue levels from two biannual crop rotations

Residue incorporation in agriculture associated with crop rotation, benefits the environment, soil fertility, and crop production. However, the benefits of conservation agriculture practices in soil fertility and crop yield increases come up after several years. To study durum wheat (Triticum turgidum L.) crop production under conservation agriculture with incorporation of residues a biannual rotation experiment was conducted in a volcanic soil in south-central of Chile.The experiment consisted was comprised of two crops, canola (Brassica napus L.) and bean (Phaseolus vulgaris L.), and four levels of residue incorporation (0%, 50%, 100%, and 200% of generated residue). Results indicated that grain yield, grain P, and residue K concentrations were higher when the previous crop was bean. Sedimentation values (SDS test), yellowness values (b), grain N concentration, grain and residue Ca concentrations, were higher when the previous crop was canola. The different leves of applied residue for the previous crop only presented effect on sedimentation values and yellowness values. Even though to obtain consistent results about the effect of different residue levels on a crop rotation experiments a larger number of crops cycles is required, the present work showed relevant results in a short time crop rotation. Highlights Bean pre-crop increases durum wheat grain yield respect to canola crop in short-time rotations. Canola pre-cop increases sedimentation and yellowness value in durum wheat grain.

Maize grain production, plant nutrient concentration and soil chemical properties in response to different residue levels from two previous crops

ABSTRACTThe incorporation of previous crop residues in agricultural management benefits soil fertility, crop production, and environment. However, there is no enough information about maximum residue application level without negative effect over next crop yield. To evaluate maize (Zea mays L.) yield under short-time conservation management with incorporation and/or importation of different residue levels, a biannual rotation experiment was conducted in ash volcanic soil in south-central Chile. The experiment consisted of two previous crops, canola (Brassica napus L.) and bean (Phaseolus vulgaris L.), and four levels of residue incorporation (0%, 50%, 100%, and 200% of generated residue; from 0 to 21.4 Mg ha−1 for canola and from 0 to 19.0 Mg ha−1 for bean). Previous crop species and residue level affected some nutrients concentrations in grain and plant and some soil chemical properties, without effect in maize yield, which averaged 16.6 Mg ha−1. Bean residue increased Ca and reduced S in maize plant, increasing soil P, Ca, Mg and K (P < 0.05). Maize grain Ca content was positively and proportionally affected by canola residue level and negatively and proportionally affected by bean residue level. All canola residue levels increased soil pH and Mg, but the highest level reduced soil S; soil P concentration increased proportionally with bean residue level. The highest bean residue level increased soil S. Different crop and levels of residue did not affect maize yield but did some plant nutrient concentration, and also affected some soil chemical properties.

Processing Tomato–Durum Wheat Rotation under Integrated, Organic and Mulch-Based No-Tillage Organic Systems: Yield, N Balance and N Loss

In a 4-year study, the biannual crop rotation processing tomato–durum wheat was applied to three cropping systems: (i) an innovative organic coupled with no-tillage (ORG+) where an autumn-sown cover crop was terminated by roller-crimping and then followed by the direct transplantation of processing tomato onto the death-mulch cover; (ii) a traditional organic (ORG) with autumn-sown cover crop that was green manured and followed by processing tomato; and (iii) a conventional integrated low-input (INT) with bare soil during the fall–winter period prior to the processing tomato. N balance, yield and N leaching losses were determined. Innovative cropping techniques such as wheat–faba bean temporary intercropping and the direct transplantation of processing tomato into roll-crimped cover crop biomass were implemented in ORG+; the experiment was aimed at: (i) quantifying the N leaching losses; (ii) assessing the effect of N management on the yield and N utilization; and (iii) comparing the cropping system outputs (yield) in relation to extra-farm N sources (i.e., N coming from organic or synthetic fertilizers acquired from the market) and N losses. The effects of such innovations on important agroecological services such as yield and N recycling were assessed compared to those supplied by the other cropping systems. Independently from the soil management strategy (no till or inversion tillage), cover crops were found to be the key factor for increasing the internal N recycling of the agroecosystems and ORG+ needs a substantial improvement in terms of provisioning services (i.e., yield).

Different Residues Affect Wheat Nutritional Composition

Conservation agriculture using crop rotation benefits the environment, soil fertility, and crop production. A biannual rotation experiment during a period of 2 years was conducted in volcanic soil in south-central Chile in a production system under conservation agriculture. The experiment considered two previous crops, canola (Brassica napus L.) and bean (Phaseolus vulgaris L.), and four levels of residue incorporation (0%, 50%, 100%, and 200% of generated residue). Grain yield (0.41 Mg ha−1), grain sedimentation value (5.5%), grain K (0.031%) and Ca (0.006%) concentrations, and residue K concentration (0.159%) were higher when the previous crop was bean. The Ca concentration (0.037%) in wheat residue increased after the canola crop. The different applied residue levels of the previous crop had no effect on any of the evaluated parameters in wheat. There was a very consistent negative correlation between the grain S concentration and the residue P (− 0.55), K (− 0.55), Mg (− 0.61), and S (− 0.63) concentrations in wheat when it was cultivated after bean. A larger number of study cycles are required to obtain more consistent results about the effect of the different residue levels on these two biannual rotations.

Soil carbon and nitrogen stocks and physical properties under no‐till and conventional tillage cotton‐based systems in the Brazilian Cerrado

AbstractThe aim of this study was to investigate soil C and N stocks and soil physical properties under a cotton (Gossypium hirsutum) based system using no‐till (NT) and conventional tillage (CT). The experiment was established as a randomized block design with four replications of six treatments as follows: [NT1], NT system with crop rotation of cotton/soybean (Glycine max)/maize (Zea mays) + brachiaria (Brachiaria ruziziensis); [NT2], NT system with crop rotation of soybean/maize + brachiaria/cotton; [NT3], NT system with crop rotation of maize + brachiaria/cotton/soybean; [CR1], CT with annual rotation (soybean/cotton); and [CR2], CT with biannual rotation (soybean/soybean/cotton) and [CT1] CT with cotton monoculture. An area of native Cerrado vegetation was used as the reference or baseline. Soil samples were obtained from 0‐ to 5‐, 5‐ to 10‐, 10‐ to 20‐, 20‐ to 30‐, 30‐ to 60‐, and 60‐ to 100‐cm depths. After 9 years of cultivation, soil under NT systems contained higher C concentrations than those under CT (p &lt; 0.05); however, significant differences were restricted to the 0‐ to 5‐cm layer. Stocks of C and N in the 0‐ to 30‐cm depth ranged from 36.2 to 39.8 Mg ha−1 and from 2.00 to 2.22 Mg ha−1, respectively. Despite higher C concentration in the upper layer, NT treatments (NT1, NT2, and NT3) had soil C stocks similar to those of CR1 and CT1. In comparison with Cerrado, C stocks in soil under all cultivated treatments were reduced by 27% in the top 1‐m depth, which represents a C loss of 35 Mg C ha−1 upon conversion from the Cerrado to cultivated land. The least soil bulk density among all treatments was observed for NT1. However, there were no differences in macroporosity and microporosity among NT and CT systems even after 9 years of cultivation. In comparison with CT, principal benefits of NT systems for C sequestration and soil physical improvements are restricted to the surface layer.

Análisis de la estrategia MasAgro-maíz

&#x0D; &#x0D; &#x0D; En este ensayo se examinan los objetivos y estrategias del programa MasAgro-maíz, partiendo de las condiciones iniciales del subsector agrícola tradicional de México que produce maíz de temporal. Estas condiciones iniciales muestran que la tendencia de los últimos 30 años ha sido de incrementar la producción nacional de maíz de temporal en 1.20 millones de toneladas anuales (MTA) y el rendimiento en 0.22 Mg ha-1, cada 10. Por lo tanto los objetivos de MasAgro habrán de ser corregidos en consecuencia. Se analiza la experiencia mundial sobre la adopción de la agricultura de conservación (AC) por parte de los productores en pequeño. Para el caso examinado de adopción de la AC con rotación bianual, se calcula que el programa ha de tratar directa o indirectamente 3.164 millones de hectáreas (M ha) manejadas por más de 800 000 unidades de producción (UP) pequeñas (categorías &lt; 5 ha y 5-20 ha) y lograr rendimientos promedio de 3.92 Mg ha-1. No obstante el reconocido efecto positivo sobre la sostenibilidad, la estrategia de adopción irreversible de la AC podrá ser pobre debido al bajo incentivo económico de plazo corto involucrado, a la falta de acceso al crédito, a apoyos a la comercialización, y varias incompatibilidades con los objetivos y demandas de bienestar de las pequeñas UP. La estrategia de sustituir entre 25y50%,delasuperficieocupadaporlosmaícesnativosylas variedades acriolladas se considera inadecuada para México, por su carácter de centro de origen del maíz y de importante reservorio de biodiversidad de la especie.&#x0D; &#x0D; &#x0D;

Enzymes and C pools as indicators of C build up in short-term conservation agriculture in a savanna ecosystem in Cambodia

Soil organic carbon (SOC) pools, particularly labile pools, and soil enzymes are good indicators of short-term impacts of soil management. We hypothesized that labile SOC pools drives C accumulation and enzyme activity can be an efficient indicator for C build up in short-term conservation agriculture. The aims of this study were to quantify the impacts of tillage and crop rotations with diverse crop residue inputs on changes in SOC labile pools and enzymatic activities in rice-, soybean- and cassava-based cropping systems designated as RcCS, SbCS and CsCS, respectively. The four treatments in each cropping system consisted of: conventional tillage (CT), no-till in which main crops (rice, soybean and cassava) were grown in a one-year frequency pattern (NT1) and, no-till in which the main crops were grown in bi-annual rotations with maize (NT2 and NT3). After 5 years experiment period, greater hot-water extractable organic C (HWEO-C) stocks of 61%, 55% and 53%, and permanganate oxidizable C (POX-C) stocks of 23%, 21% and 32% were attributed to NT than those in CT soils under RcCS, SbCS and CsCS, respectively, at 0–5 cm soil layer. The pyrophosphate extractable organic C (PEO-C) and chemically stabilized organic C (CSO-C) stocks were almost constant in each depth among treatments, except 0–5 cm in CsCS. The β-glucosidase activity was 18%, 28% and 49% greater in NT than those in CT soils at 0–5 cm under RcCS, SbCS, CsCS, respectively. Arylsulfatase activity was 36% and 39% greater in NT than in CT under SbCS and CsCS, respectively but no significant differences in RcCS. A strong and positive correlation (P < 0.001) between β-glucosidase and arylsulfatase activity with POX-C, HWE-C, SOC and total N indicated how these variables were inter-related. Comparison among three NT treatments, bi-annual crop rotations showed a better increasing trend of HWEO-C, POX-C and enzymatic activities than those with one-year frequency pattern. In conclusion, short-term NT crop rotations with permanent soil cover significantly increased the storage of HWEO-C and POX-C and enhanced β-glucosidase and arylsulfatase activities at the surface soil layer as a result of higher biomass-C input and the absence of soil disturbance.

Stable nutrient flows in sustainable and alternative cropping systems of globe artichoke

The conventional cultivation of globe artichoke causes high nitrogen (N) balance surpluses. The planning of more sustainable open-field horticultural systems (with no synthetic fertilizer supply) can contribute to the reduction of the nutrient surplus. We hypothesized that an artichoke conventional system could be shifted to a sustainable system through mineral fertilizer supply based on expected plant nutrient uptake, return of crop residues in well-defined growth phases, use of fertility-building crops, and crop rotations. Over a 10-year field experiment, three management systems, differing in fertilizer rates, crop sequence (monoculture/rotation with cauliflower), and legume cover crop adoption and management, were compared: (i) improved conventional, (ii) alternative monoculture, and (iii) biannual rotation. We monitored soil conditions at a sampling interval of approximately 3 years. We calculated gross N, P, and K balances for each growing season, and we also monitored soil respiration over the last two growing seasons. On average, the biannual rotation resulted in a well-balanced N budget (72 kg ha−1 N surplus) compared with improved conventional (160 kg N ha−1 N surplus) and alternative monoculture (− 34 kg ha−1 deficit) systems. By contrast, compared with the improved conventional system (133 and 116 kg ha−1 for P and K budgets, respectively), alternative monoculture and biannual rotation systems had negative budgets for P (− 9 kg ha−1 for both alternative systems) and K (− 58 and − 51 kg ha−1 for alternative monoculture and biannual rotation systems, respectively) in nine of ten growing seasons. Our results show for the first time that long-term biannual rotation with cauliflower coupled with cover crop use can optimize nutrient fluxes of conventionally grown globe artichoke. Overall, the study proposes a re-design of artichoke cropping systems, provides novel information useful for growers, and verifies that introducing a legume species cover crop is also the most promising approach to foster long-term sustainability.

Crack formation in a mediterranean rainfed Vertisol: Effects of tillage and crop rotation

The frequency, size and development rate of Vertisols cracks influence the water, solute and heat dynamics and hence on the crop productivity. The aim of this study was to evaluate the effect of the tillage system and crop rotation on the behaviour of cracks and soil compaction in a long-term experiment that was initiated in 1986 on a Mediterranean rainfed Vertisol in southern Spain. The treatments studied were conventional tillage (CT) vs. no-tillage (NT) for five crop rotations: wheat (Triticum aestivum L.) - chickpea (Cicer arietinum L.), wheat - sunflower (Helianthus annuus L.), wheat - faba bean (Vicia faba L.), wheat - bare fallow and continuous wheat. The following parameters were measured: penetration resistance, water content at harvest, and perimeter, depth and width of crack. Soil compaction was greater in NT compared to CT in the top 10cm of soil, with the opposite occurring between 10 and 40cm. The surface area and volume of cracks was significantly greater in CT than in NT. The perimeter of the cracks was greater in wheat monoculture plots but with smaller crack width and depth in relation to the other studied biannual rotations. The water content at harvest recorded in the first 30cm of soil was negatively correlated with the depth of cracks. The characterization of the cracks in Vertisols is very important for estimating losses or recharging the water in the soil profile as well as for evaluating its compaction and stability.

Long-term bioenergy sorghum harvest strategy and soil quality

A long-term study was initiated in 2008 to determine effects of bioenergy sorghum [Sorghum bicolor (L.) Moench.] production on soil quality. Sorghum biomass removal may potentially deteriorate soil quality and productivity through nutrient removal and decreased organic matter return. Study treatments included continuous bioenergy sorghum and a sorghum/corn (Zea mays L.) biannual rotation, 0, 25, or 50% return of harvested sorghum biomass, no or non-limiting N addition, and a complete nutrient return treatment. The study was conducted near College Station, TX on Weswood silty clay loam soil. Soil quality indicators including soil organic carbon (SOC), total soil nitrogen (TSN), and soil C:N ratio were determined in soil samples collected annually at five depth increments to 90 cm for seven years (2009–2015) and compared to initial values in 2008. The greatest sorghum biomass yield increase from residue return was observed with 25% return and N fertilization. Nitrogen was essential for biomass and biomass C yield for both sorghum cropping systems, especially continuous sorghum. Increasing residue return from 25 to 50% tended to increase SOC in the near surface regardless of N addition, but generally not with depth. From the initial year in 2008 to 2015, SOC increased at all soil depths, except 15–30 cm, under continuous sorghum receiving residue return and N fertilization. Increases in SOC were much higher with continuous than rotated sorghum. For example, SOC storage for fertilized rotated sorghum averaged across residue return rates increased by 10% (59.4 to 65.1 Mg ha−1) and for continuous sorghum by 51% (59.4 to 90.1 Mg ha−1) by 2015 compared to initial values in 2008. For both continuous and rotated sorghum, changes in SOC stocks were greater in lower depths, principally at 30–60 and 60–90 cm, implying that SOC increases at these depths were most likely associated with bioenergy sorghum roots. After seven years of 25% residue return, SOC increased by 1.75, 5.25, 15.4, 32.9, and 39.2 Mg ha−1, respectively, at 0–5, 0–15, 0–30, 0–60, and 0–90 cm. Total soil N to 90 cm depth tended to follow similar patterns as those observed for SOC storage. Soil C:N ratio also tended to increase in all depth increments with residue return, but especially in the surface 0–5 cm with N fertilization. The highest C:N ratio increase were observed in surface soil under continuous sorghum at 25 and 50% residue return rates with or without N fertilization. Increased soil C:N at deeper depths in continuous sorghum was probably associated with sorghum roots. The return of 25% of aboveground biomass from a continuous sorghum cropping system in conjunction with N fertilization appeared feasible for maintaining soil quality in the long term.

Short-term conservation agriculture and biomass-C input impacts on soil C dynamics in a savanna ecosystem in Cambodia

Conservation agriculture (CA) is an effective tool that is used to increase soil C sequestration and enhance soil quality and agronomic productivity. However, rigorous empirical evidence from Southeast Asia, particularly in the Cambodian agro-ecosystem, is still scarce. We hypothesized that high and diversified biomass-C inputs in CA might be the first step toward to increase SOC in the topsoil by creating the C flow to support C storage overtime. Thus, the aim of this study was to quantify the short-term (i.e., five year) impacts of soil management and cropping systems on soil organic C (SOC), soil total N (STN), particulate organic C (POC) and mineral-associated organic C (MAOC). There were three distinct experiments comprised of a combination of cover and main crops including rice-, soybean- and cassava-based cropping systems, hereafter designated as RcCS, SbCS and CsCS, respectively. The experimental plots were laid out in a randomized complete block design with three replicates. Soil management treatments included conventional tillage (CT) and no-till (NT) and a selected adjacent area of reference vegetation (RV). Soil sampling was conducted in 2011 and 2013 at seven depths (0–5, 5–10, 10–20, 20–40, 40–60, 60–80 and 80–100cm). Soil management and crop sequences significantly affected SOC and STN stocks in all three cropping systems. On average, NT SOC stocks at 0–5cm depth was greater than those of CT by 10%, 20% and 18% and STN stocks by 8%, 25% and 16% for RcCS, SbCS and CsCS, respectively. SOC levels followed the order RV>NT>CT. SOC stocks in the subsoil layers were consistently lower in NT than in CT in all three cropping systems. POC stocks at 0–5cm depth in NT were on average 22%, 20% and 78% greater than those in CT in RcCS, SbCS and CsCS, respectively. However, significant differences were detected only in RcCS and CsCS. The major POC stocks were found at 0–20cm depth. NT treatments in SbCS stored 9% greater MAOC stocks at 0–5cm depth than those in CT, and an increasing trend of NT was observed in RcCS and CsCS. In all three cropping systems, NT systems with diversified crop species significantly increased SOC stocks ranging by 6 to 28% and POC stocks by 56–127% in the surface soils and tended to restore SOC and POC in the subsoil layers after five years. The results leads to accept the hypothesis that short-term CA associated with high biomass-C inputs (particularly bi-annual rotations) promotes SOC recovery in the topsoil layer and creates a potential to increase SOC in the subsoil layers when deep-rooting cover crops are included in crop rotations.

Modeling the effect of soil structure on water flow and isoproturon dynamics in an agricultural field receiving repeated urban waste compost application

Transport processes in soils are strongly affected by heterogeneity of soil hydraulic properties. Tillage practices and compost amendments can modify soil structure and create heterogeneity at the local scale within agricultural fields. The long-term field experiment QualiAgro (INRA–Veolia partnership 1998–2013) explores the impact of heterogeneity in soil structure created by tillage practices and compost application on transport processes. A modeling study was performed to evaluate how the presence of heterogeneity due to soil tillage and compost application affects water flow and pesticide dynamics in soil during a long-term period. The study was done on a plot receiving a co-compost of green wastes and sewage sludge (SGW) applied once every 2years since 1998. The plot was cultivated with a biannual rotation of winter wheat–maize (except 1year of barley) and a four-furrow moldboard plow was used for tillage. In each plot, wick lysimeter outflow and TDR probe data were collected at different depths from 2004, while tensiometer measurements were also conducted during 2007/2008. Isoproturon concentration was measured in lysimeter outflow since 2004. Detailed profile description was used to locate different soil structures in the profile, which was then implemented in the HYDRUS-2D model. Four zones were identified in the plowed layer: compacted clods with no visible macropores (Δ), non-compacted soil with visible macroporosity (Γ), interfurrows created by moldboard plowing containing crop residues and applied compost (IF), and the plow pan (PP) created by plowing repeatedly to the same depth. Isoproturon retention and degradation parameters were estimated from laboratory batch sorption and incubation experiments, respectively, for each structure independently. Water retention parameters were estimated from pressure plate laboratory measurements and hydraulic conductivity parameters were obtained from field tension infiltrometer experiments. Soil hydraulic properties were optimized on one calibration year (2007/08) using pressure head, water content and lysimeter outflow data, and then tested on the whole 2004/2010 period. Lysimeter outflow and water content dynamics in the soil profile were correctly described for the whole period (model efficiency coefficient: 0.99) after some correction of LAI estimates for wheat (2005/06) and barley (2006/07). Using laboratory-measured degradation rates and assuming degradation only in the liquid phase caused large overestimation of simulated isoproturon losses in lysimeter outflow. A proper order of magnitude of isoproturon losses was obtained after considering that degradation occurred in solid (sorbed) phase at a rate 75% of that in liquid phase. Isoproturon concentrations were found to be highly sensitive to degradation rates. Neither the laboratory-measured isoproturon fate parameters nor the independently-derived soil hydraulic parameters could describe the actual multiannual field dynamics of water and isoproturon without calibration. However, once calibrated on a limited period of time (9months), HYDRUS-2D was able to simulate the whole 6-year time series with good accuracy.

Stratification ratio of organic matter pools influenced by management systems in a weathered Oxisol from a tropical agro-ecoregion in Brazil

Enhancement of organic matter plays an essential role in improving soil quality for supporting sustainable food production. Changes in carbon stocks with impacts on emissions of greenhouse gases may result from the stratification of organic matter as a result of soil use. The objective of this study was to evaluate the impact of soil management systems on soil carbon stocks and stratification ratios (SR) of soil organic matter pools. Total organic carbon (TOC), particulate organic carbon (POC), mineral-associated organic carbon, microbial biomass carbon (MBC) and nitrogen, basal respiration, and particulate organic matter nitrogen (PON) were determined. The field experiment comprised several tillage treatments: conventional tillage, no-till with biannual rotation, no-till with biannual rotation combined with a second crop, no-till with annual rotation, and pasture. The labile fractions indicated a high level of variation among management systems. Pasture proved to be an excellent option for the improvement of soil carbon. While the conventional tillage system reduced total carbon stocks of the soil (0–40 cm), no-tillage presented TOC stocks similar to that of native vegetation. Sensitivity of the TOC SR varied from 0.93 to 1.28, a range of 0.35; the range for POC was 1.76 and for MBC 1.64. The results support the hypothesis that the labile fractions (POC, MBC, and PON) are highly sensitive to the dynamics of organic matter in highly weathered soils of tropical regions influenced by different management systems. Reductions to SRs of labile organic matter pools are related to the impacts of agricultural use of Cerrado soils.

Evidence for increased monoculture cropping in the Central United States

While crop rotation patterns can be complex with multiple crops rotated over several years, the most common rotation practice in the Central United States is biannual rotation between corn and soybeans. We analyzed the changes in crop rotation patterns from 2003 to 2010 using the Cropland Data Layer (CDL), which provides remotely sensed land cover layers for agricultural crops in the Central United States. The accuracy of the CDL was validated by comparing the total acreage for a state or county present in the CDL with the total planted crop acreage available from the National Agricultural Statistics Service. The data layers were combined into two time periods 2003–2006 and 2007–2010, and specific rotation patterns were determined for every location in the study area. The combinations resulted in unique sequences such as single, double, triple and quadruple, the latter of which is equivalent to the same crop class present all four years at a particular location. Corn and soybeans were analyzed to determine the amount of area used for production as well as the amount of change between unique crop rotation sequences. While the total area under production of major crops in the second half of our study period increased only slightly, the extent to which major crops (e.g., corn and soybeans) were grown in continuous cropping sequences increased significantly. For example, the amount of land impacted by corn in the first time period increased by only 2% in the second time period. However, the amount of corn grown in quadruple sequence doubled from the first half to the second half of our study period. We conclude that, although crop rotation patterns are very complex in this region, involving considerable amount of non-cropland, the footprint of major crops such as corn have moved toward monoculture cropping practices in the last decade.