Maize Straw Incorporation Research Articles

Soil Greenhouse Gas Emissions and Nitrogen Dynamics: Effects of Maize Straw Incorporation Under Contrasting Nitrogen Fertilization Levels

Straw is widely incorporated into conservation agriculture around the world. However, its effects on greenhouse gas emissions (GHGs) and nitrogen dynamics under soils formed by the long-term application of different amounts of nitrogen (N) fertilizer are still unclear. An incubation experiment was conducted on soils collected from a field study after 6 years of contrasting N fertilization of 0 (low N), 187 (medium N), and 337 kg N ha−1 (high N), with and without maize straw. Straw amendment significantly stimulated both nitrous oxide (N2O) and carbon dioxide (CO2) fluxes (p < 0.05), and increased cumulative emissions by 0.8 and 19.0 times on average compared to those without straw incorporation. Medium-N soil observably weakened N2O emissions (23.8 μg kg−1) compared to high-N soil (162.7 μg kg−1), and increased CO2 emissions (1.9 g kg−1) compared to low-N soils (2.3 g kg−1) with straw amendment. Soil NH4+-N and NO3−-N invariably increased with rising soil N level, whereas straw promoted the turnover of mineral N by enhancing soil N fixation capacity. From the first day until the end of incubation, NH4+-N decreased by 79.0% and 24.7%, while NO3−-N showed a decrease of 58.8% or an increase of 75.2%, depending on whether straw was amended or not, respectively. Moreover, partial least squares path modeling and random forest mean predictor importance were used to find that straw affected GHGs by altering the N turnover capacity. Straw amendment increased GHGs and diminished the risk of losing mineral N by enhancing its turnover. Combining straw with medium-N soil could mitigate the greenhouse effect and improve the N and carbon (C) balance in farming systems compared to low- and high-N soils. This is recommended as a farmland management strategy in Northeast China.

Divergent accumulation of microbial necromass and plant lignin phenol induced by adding maize straw to fertilized soils

Plant carbon (C) inputs and their subsequent microbial transformation affect the build-up process of soil organic C (SOC) pool. Nevertheless, there are knowledge gaps on how crop straw addition modifies SOC composition at molecular-level, especially in soils with different fertilization practices. Here, long-term fertilized Mollisols (unfertilized control, NF; inorganic fertilization, IF; inorganic fertilization plus manure, IFM) were incubated with or without maize straw addition in a 900-day field mesocosm experiment. The microbial necromass and plant lignin components contents were synchronously quantified based on amino sugar and lignin phenol biomarkers, respectively. And changes in SOC chemical composition were examined using solid-state 13C nuclear magnetic resonance spectroscopy. Relative to the NF treatment, long-term fertilization increased amino sugar and lignin phenol contents, and manure application enhanced the accumulation of plant lignin components more than that of microbial necromass. Compared with the NF treatment, the IF treatment decreased the relative proportion of alkyl C and SOC content, suggesting that changes in microbial necromass and lignin phenol were not always consistent with changes in SOC. For the NF and IF treatments, maize straw incorporation increased both amino sugar content and its contribution to SOC, indicating that microbial anabolism was important for SOC accumulation after adding maize straw in C-poor soils. For the IFM treatment, maize straw addition decreased lignin phenol content (27 %) and its contribution to SOC but increased the contribution of amino sugar to SOC, reflecting an enlarged contribution of microbial necromass to soil C pool formation under manure application after maize straw addition. The contribution of lignin phenol to SOC was decreased from days 360–900, whereas fungal necromass C content and the contribution of amino sugar to SOC were increased from days 360–900 under the IFM soil with maize straw addition, indicating that plant lignin components might be converted into fungal biomass and its necromass with increasing maize straw decomposition under manure application. Overall, we concluded that maize straw addition favored microbial immobilization in all fertilization treatments.

The impact of maize straw incorporation on arsenic and cadmium availability, transformation and microbial communities in alkaline-contaminated soils

Increasing evidence of the uncertainty of crop straw returning in heavy metal-contaminated soil is a significant concern. The present study investigated the influence of 1 and 2% maize straws (MS) amendment on As and Cd bioavailability in two different alkaline soils (A-industrial and B-irrigation) after 56 days of ageing. Adding MS to the two soils decreased the pH by 1.28 (A soil) and 1.13 (B soil) and increased the concentration of dissolved organic carbon (DOC) by 54.40 mg/kg (A soil) and 100.00 mg/kg (B soil) during the study period. After 56 days of ageing, the overall NaHCO3–As and DTPA-Cd increased by 40% and 33% (A) and 39% and 41% (B) soils, respectively. The MS additions increased the alteration of As and Cd exchangeable and residual fractions, whereas advanced solid-state 13C nuclear magnetic resonance (NMR) revealed that alkyl C and alkyl O–C–O in A soil and alkyl C, Methoxy C/N-alkyl, and alkyl O–C–O in B soil significantly contributed to the As and Cd mobilisation. Collectively, 16 S rRNA analyses revealed Acidobacteria, Firmicutes, Chloroflexi, Actinobacteria and Bacillus promoted the As and Cd mobilisation following the MS addition, while principle component analysis (PCA) demonstrated that bacterial proliferation significantly influenced MS decomposition, resulting in As and Cd mobilisation in the two soils. Overall, the study highlights the implications of applying MS to As- and Cd-contaminated alkaline soil and offers the framework for conditions to be considered during As- and Cd-remediation efforts, especially when MS is the sole remediation component.

Tillage with straw incorporation reduces the optimal nitrogen rate for maize production by affecting crop uptake, utility efficiency, and the soil balance of nitrogen

AbstractUnderstanding the combined effects of tillage and straw incorporation on grain yield and nitrogen (N) fertilizer utilization is vital for sustainable agriculture in northeastern China. How various tillage patterns with straw incorporation affect soil N balance and optimal N rate for crop production remains largely unknown. A four‐year (2015–2018) field experiment was conducted to assess the impact of rotary tillage with maize straw incorporation (RTS) and plough tillage with straw incorporation (PTS) combined with different N fertilizer rates (0, 112, 187, 262, and 337 kg N ha−1) on maize yield, N uptake, soil N balance, nitrogen use efficiency, and optimal N rate. In general, higher straw N uptake and lower N partial factor productivity, N use efficiency, and recovery of applied N in grains were obtained under PTS than under RTS. Moreover, grain yield and both straw and grain N uptake increased with the N application rate. However, no further increase in grain yield was observed when the applied N exceeded 187 kg N ha−1. PTS resulted in a higher level of unaccounted N from applied N fertilizer (38–81 kg N ha−1) than RTS. A high N fertilizer input (>262 kg N ha−1) combined with straw incorporation resulted in a high soil mineral N profit and substantially increased unaccounted N (614–715 kg N ha−1) over the four‐year field trial period. The optimal N input required for the highest maize yield could be reduced by 35.0%–44.6% using tillage with straw return. Nevertheless, PTS was more effective than RTS at lowering the optimal N application rate. Overall, the results of this short‐term maize field study conducted in northeastern China suggest that the amount of N fertilizer input required for maize production could be reduced by using tillage with continuous straw incorporation.

Key soil properties influencing infiltration capacity after long-term straw incorporation in a wheat (Triticum aestivum L.)–maize (Zea mays L.) rotation system

Straw incorporation is increasingly being adopted in wheat (Triticum aestivum L.)–maize (Zea mays L.) rotation systems to improve soil physiochemical properties. To identify the main soil properties influencing infiltration capacity under long-term straw incorporation in a wheat–maize rotation system, the study set four treatments: no straw incorporation and fertilizer application, wheat straw incorporation with 276 kg nitrogen/ha, wheat and maize straw incorporation with 276 kg N/ha, and wheat and maize straw incorporation. The initial, average, and final infiltration rates were calculated to represent soil infiltration capacity. Compared with other treatments, wheat straw incorporation with 276 kg nitrogen/ha treatment significantly decreased soil bulk density, soil aggregate (DMWD) mean weight diameter measured using the dry sieving method, and weight rate of soil aggregates with diameters greater than 0.25 mm measured using the wet sieving method, and significantly increased total soil porosity, soil capillary porosity, field capacity, and weight rate of soil aggregates with diameters less than 0.25 mm measured using the wet sieving method. In contrast, wheat and maize straw incorporation treatment significantly increased soil bulk density and noncapillary porosity, but decreased total soil porosity, capillary porosity, and field capacity. The results of partial least squares regression indicated that the soil moisture content and DMWD were the primary factors influencing initial infiltration rate with positive regression coefficient. Higher total soil porosity, capillary porosity, field capacity, and DMWD contributed to higher final infiltration rate, while higher soil bulk density and noncapillary porosity were correlated with a lower final infiltration rate. The key influencing factors of average infiltration rate were soil bulk density, soil moisture content, total soil porosity, capillary porosity, and DMWD. The wheat straw incorporation with 276 kg nitrogen/ha treatment had higher infiltration rates than no straw incorporation and fertilizer application treatment. However, with an increase in straw amount, the influence of straw on infiltration showed a law of diminishing marginal returns. Therefore, wheat and maize straw incorporation with 276 kg nitrogen/ha treatments had a lower infiltration rate than wheat straw incorporation with 276 kg nitrogen/ha treatment. In addition, wheat and maize straw incorporation treatment had the lowest average and final infiltration rates of all treatments, indicating that excessive straw incorporation without nitrogen fertilizer had adverse effects on infiltration rates. This study furthers understanding of the influence of long-term straw incorporation on soil hydrological processes and helps rationally use straw resources in wheat–maize rotation systems.

Soil microbial communities under wheat and maize straw incorporation are closely associated with soil organic carbon fractions and chemical structure

The incorporation of different types of crop straw may lead to distinct forms and chemical structures of soil organic matter (SOM), which are closely associated with the communities of soil microorganisms in agricultural ecosystems. However, the relationships between the physiochemical composition of SOM and soil microbial communities in response to the incorporation of different types of crop straw remain largely unknown. In this study, we sought to gain insights into these relationships based on a long-term (10 year) field experiment, in which we examined the effects of five treatments [no fertilizer (control), mineral fertilizer (F), mineral fertilizer and wheat straw return (WF), mineral fertilizer and maize straw return (MF), and mineral fertilizer with wheat and maize straw (WMF)]. Using advanced solid-state 13carbon (C) nuclear magnetic resonance and high-throughput sequencing techniques, we investigated the associations between SOM physical fractions and chemical composition and the compositions of soil fungal and bacterial communities Our observations indicated that compared with treatment MF, the long-term incorporation of wheat straw increased the proportions of carbohydrate carbons in light-fraction and coarse-particulate organic matter (cPOM), which were significantly correlated with soil bacterial community composition. Long-term maize straw incorporation was found to increase the proportions of course and fine-POM fractions relative to the WF treatment, as well as the proportions of their aromatic carbons, which were significantly correlated with soil fungal community composition. Collectively, the findings of this study revealed that bacterial and fungal communities are characterized by two distinct responses to wheat and/or maize straw incorporation, which are strongly associated with the physical fractions and chemical structure of SOM, particularly in the case of POM. These findings provide valuable insights for understanding the associations between soil microbial communities and SOM fractions following crop straw incorporation, which will contribute to the development of optimal strategies for crop straw management.

Soil organic carbon and nitrogen fractions as affected by straw and nitrogen management on the North China Plain

Straw incorporation and nitrogen (N) application play crucial roles in regulating soil carbon (C) and N storage and availability. However, their effects on soil C and N fractions and microbial community composition, as well as the relationships between microorganisms and soil organic C (SOC) and soil organic N (SON) fractions remain largely unexplored. Here, arable soils following 5-year straw (NS, nonamended controls; AS, wheat and maize straw incorporation) and N (0, 150 and 250 kg N ha−1 applied for each crop) management were collected to determine the organic C and N fractions and microbial community composition. Compared to NS, AS significantly increased the contents of SOC and total nitrogen (TN) by 36.26 % and 24.12 %, respectively, mainly by increasing the contents of dissolved organic carbon (DOC), particulate organic carbon (POC), hydrolysable unknown-N (HUN) and acid insoluble-N (AIN). Under straw incorporation, N addition significantly improved total phospholipid fatty acids (PLFAs), the contents of TN, DOC, amino acid-N (AAN), active SON and stable SON, and the ratios of POC/SOC and DOC/SOC. However, there was no significant difference in SOC pool, organic C and N fractions (except for AAN and active SON) and microbial community composition between the N150 and N250 levels under AS. Compared to straw removal, straw incorporation significantly changed the microbial community composition by increasing the accumulations of SOC, DOC, POC, and mineral-associated organic carbon (MAOC). Regression analysis indicated that high relative abundances of fungi and gram-positive bacteria (GP) were more conducive to stable SON accumulation. Collectively, straw incorporation coupled with 150 kg N ha−1 per crop growing season was a sustainable field management practice for effectively improving soil fertility on the North China Plain.

Difference of Soil Bacterial and Fungal Communities Under Wheat and Maize Straw Incorporation Closely Related to Fractions and Chemical Structure of Soil Organic Carbon

Difference of Soil Bacterial and Fungal Communities Under Wheat and Maize Straw Incorporation Closely Related to Fractions and Chemical Structure of Soil Organic Carbon

Nitrogen Fertilizer Management and Maize Straw Return Modulate Yield and Nitrogen Balance in Sweet Corn

Nitrogen fertilizer is an important component of crop production; however, its excessive application could result in N loss that could have serious environmental concerns. Straw incorporation in the soil after crop harvest is one of the most feasible straw management techniques, however, the optimization of nitrogen (N) fertilizer management and maize straw incorporation to modulate the crop yield and to maintain N balance in sweet corn is necessary to get better yields on a sustained basis. The present study was comprised of two straw management treatments i.e., (i) no straw return (S0), and (ii) incorporation of crushed corn ears by into the soil using rotary tiller (S100) and four N fertilizer management treatments i.e., (i) common farmer practice with total N applied at 300 kg ha−1 with 50%, 5%, 30%, and 15% splits at basal, 3-leaf stage (V3), at hilling stage (V8) and at tasseling/flowering stage (RT), respectively (FM); (ii) application of total N at 225 kg ha−1 with 40%, 10% and 50% at basal, 3-leaf stage (V3) and at hilling stage (V8), respectively (OMI); (iii) application of total N at 150 kg ha−1 with 40%, 10% and 50% at basal, 3-leaf stage (V3), and at hilling stage (V8), respectively (OMII); and (iv) the treatment without any fertilizer application (N0). The hybrid sweet corn cultivar ‘Yuetian 28’ was grown during the spring and autumn growing seasons of 2016 and 2017. The results showed that the N management treatments substantially improved the fresh ear yield, ear number and ear weight, partial factor productivity from nitrogen (PFPN), recovery efficiency from nitrogen (REN), and agronomic efficiency from nitrogen (AEN). Compared with FM, the OMI and OMII treatments significantly increased the AEN and PFPN whilst decreased the apparent N loss, however, the fresh ear yield, ear number and ear weight in OMI treatment were found to be statistically similar (p ˃ 0.05) to FM. Moreover, the S100 treatment did not affect the fresh ear yield and yield components significantly. Overall, straw return combined with an optimized N fertilizer application could improve the yield of sweet corn on a sustained basis with minimum and/or negligible N loss.

Effects of mineral phosphorus fertilizer reduction and maize straw incorporation on soil phosphorus availability, acid phosphatase activity, and maize grain yield in northeast China

ABSTRACT The partial substitution of mineral phosphorus (P) fertilizer by crop straw can mitigate its consumption and losing risk to the environment. However, the changes in soil P availability, acid phosphatase (AcP) activity, and grain yield under mineral P fertilizer reduction and crop straw incorporation remain poorly understood. This study evaluated the effects of a 20% reduction in mineral P fertilizer plus maize straw addition on soil P availability, AcP activity, and maize grain yield, as well as their relationships in a 5-year continually planted maize field in northeast China. Results showed that five years of continuous 20% of mineral P fertilizer reduction and maize straw incorporation significantly increased soil NaHCO3-Po and NaOH I-Pi concentrations, and did not decrease soil labile inorganic P concentration and grain yield compared to the treatment where 100% mineral P fertilizer was applied without straw addition. Additionally, there were significant positive correlations between soil AcP activity, labile inorganic P concentration, and grain yield, indicating AcP might play an important role in maintaining soil P availability and grain yield. Overall, the addition of maize straw can effectively replace 20% of the mineral P fertilizer and could be used as an appropriate fertilization practice in northeast China.

The effects of straw incorporation with plastic film mulch on soil properties and bacterial community structure on the loess plateau

AbstractThe application of plastic film mulch and the return and incorporation of crop straw into topsoil as independent treatments affect soil physicochemical properties, including nutrient balance/cycling. It remains unclear whether combining straw incorporation and plastic film mulch significantly affects soil physicochemical properties and bacterial communities. We conducted a two‐factor (plastic film mulch application and maize straw incorporation) randomized block design experiment with four treatments: no plastic film mulch or straw incorporation (C), plastic film mulch (M), straw incorporation without mulch (CS) and straw incorporation with mulch (MS). Soil was sampled at the end of the growing cycle after 3 years of treatment. Soil organic carbon (SOC), total nitrogen (TN) and nitrate‐nitrogen (NO3−‐N) concentrations significantly improved after straw incorporation. Plastic film mulch had a significant negative effect on soil bacterial richness, whereas straw incorporation had no effect. Straw incorporation had a significant positive effect on bacterial diversity, whereas plastic film mulch had no effect. The MS and M treatments had significantly more Proteobacteria than the C and CS treatments. Formation of the soil bacterial community structure was driven by soil TN, NO3−‐N and SOC in the treatments with straw incorporation, and soil ammonium‐nitrogen (NH4+‐N) in the treatments without straw incorporation. In conclusion, plastic film mulch coupled with straw incorporation can significantly change the taxonomical and functional composition of soil bacterial communities and enhance soil bacterial diversity by affecting carbon and nitrogen cycling in cropland soils of farmland, especially in arid and semiarid regions.Highlights SOC, TN and NO3−–N concentrations significantly improved after straw incorporation Straw incorporation had a greater effect on bacterial communities than plastic film mulch Soil bacterial community structure was driven by soil TN, NO3−–N and SOC after straw incorporation Soil bacterial community structure was driven by soil NH4+‐N without straw incorporation.

Impacts of residue quality and N input on aggregate turnover using the combined 13C natural abundance and rare earth oxides as tracers

The effects of residue quality and nitrogen (N) input on soil aggregate turnover are not clarified. In this study, aggregation pathways and C cycling were tracked by using rare earth oxides (REOs) and 13C natural abundance as tracers, respectively. Two residues (maize straw, C/N = 32; miscanthus straw, C/N = 220) coupled with or without N application (200 kg N ha−1) were incorporated into the REO labelled soil (δ13C = −23.2‰). Soil respiration, aggregate stability (MWD), REO concentrations and 13C were measured after 0, 7, 14 and 28 days of incubation. The maize straw incorporation resulted in a greater soil respiration and MWD as compared with the poor residue quality miscanthus straw. The N addition improved the miscanthus straw decomposition and MWD, whereas this effect was negligible for the maize straw treatments. The change in the MWD was related to the soil respiration (P < 0.001). As a result, the aggregate turnover of the soil incorporated with maize straw was faster than that of the soil incorporated with miscanthus straw. The N input increased the aggregate turnover of the soil incorporated with miscanthus straw but this effect was minimal for the maize straw amended soil. The new C accumulated more, but decomposed faster in macroaggregates than in microaggregates. A significant positive relationship was observed between the 13C concentration and the aggregate turnover rate (P < 0.01) in sole straw amended treatments, whereas this relationship became weak after N input. Our results demonstrate that aggregate turnover depends on the residue quality and N input when the residue decomposition is under N-limited conditions.

Transformation and stabilization of straw residue carbon in soil affected by soil types, maize straw addition and fertilized levels of soil

Soil organic carbon (SOC) sequestration is influenced by incorporation of maize straw and application of fertilizers, in intensive agricultural regions. However, there is a limited understanding of the transformation and stabilization of the newly added carbon (C) in soils applied with different amounts of straw residue. The aim of this study was to quantify the relationship between straw C input and SOC sequestration across soil types. We applied 13C-labeled maize straw (at amounts of 0 g, 1 g, 3 g, 5 g, 10 g per 100 g dried soil), combined with an in-situ carborundum tube method, in fertilized and non-fertilized Phaeozem and Luvisol soils at experimental sites in Northeast China. Over a period of 360 days, we found that the added amounts of maize straw, and fertilization, affected the residual rates, distribution and stabilization of extraneous new C. Fertilized treatments resulted in lower residual rates of maize straw at the end of the experimental period compared with non-fertilized treatments. We observed that the increased SOC from maize straw amendment (1.08 g C kg−1, the average for all treatments) could not compensate for the loss of native SOC (2.49 g C kg−1 soil, the average for all treatments) with 1 × C maize straw input. However, 5 × C and 10 × C straw addition were enough to offset the native SOC loss. An increase in maize straw incorporation with non-fertilized treatments caused the largest increase in new SOC formation which was highest (84.5%) for 10 × C maize straw input at the end of 360 days incubation at the Luvisol site. With increasing C input, turnover rate was observed to increase from 0.06 (1 × C) to 5.07 year−1 (10 × C), and the C turnover in each level of maize straw addition decreased with incubation time. These results demonstrate that soil type, fertilizer application, and a threshold amount of maize straw input are needed to drive net SOC sequestration.

Changes in soil characteristics and maize yield under straw returning system in dryland farming

Inappropriate fertilization has negative effects on soil quality and utilization of soil water storage. The effects of maize straw incorporation at low (LS 4500 kg ha−1), medium (MS 9000 kg ha−1), and high (HS 13,500 kg ha−1) rates combined with chemical fertilizers on soil properties, maize yield and water-use efficiency (WUE) compared with chemical fertilizers (CK) were researched over 5 years under semi-humic conditions in dark loessial soil. The duration of decreased soil bulk density after straw incorporation depended on the straw incorporation rate; compared with CK, only HS treatment significantly decreased soil bulk density from the fourth year of the experiment and onward. Annual straw incorporation had cumulative effects on the build-up of soil enzyme activity. Soil fertility and enzyme activities were significantly improved with increasing straw incorporation rate over time. Straw incorporation rate decided the duration of increased crop yield and WUE; compared with CK, MS and HS treatments had 8.0–39.5% higher maize yield and 6.2–36.8% higher WUE in the five experimental years, whereas LS treatment significantly increased maize yield after the second fertilization year and significantly enhanced WUE after the fifth fertilization year. After the fourth fertilization year, MS treatment had no significant difference with HS treatment on maize yield and WUE. The rational straw incorporation treatment is MS in terms of improving dryland soil fertility, crop product and WUE.

Coupled incorporation of maize (Zea mays L.) straw with nitrogen fertilizer increased soil organic carbon in Fluvic Cambisol

Soil organic carbon (SOC) level is influenced by incorporation of crop straw and application of nitrogen (N) fertilizer, which are typical farming practices in intensive agricultural regions. However, the interaction between the N fertilization and crop straw incorporation on SOC levels is still not univocally established, especially for calcareous soils. We therefore conducted a 224-day laboratory incubation experiment with four levels of 13C-labeled maize straw amendment (0, 1×, 3× and 5× of maize straw yield) and three N fertilization rates (0, 300, and 600kgNha−1a−1) on a Fluvic Cambisol to investigate the short-term response of SOC content. The 13C-labeled straw allowed partitioning of the CO2 produced from native SOC or crop straw for application to a two-compartment exponential decay model to simulate the addition of new SOC from the straw and the decomposition of the native SOC. The addition of maize straw caused immobilization of inorganic N during the incubation. Increased mineral N fertilization significantly inhibited the decomposition of maize straw, which led to the increased new SOC from maize straw amendment. Priming effect (PE) of native SOC decomposition peaked at 40days after incubation, and then decreased until the end of the incubation. N fertilization significantly enhanced the cumulative PE when maize straw was not added (N2 induced PE at C0 was +19% of C0N0 SOC decomposition), but had no significant effect when the highest rate maize straw was amended (N2 induced PE at C5 was 8% of C0N0 SOC decomposition), indicating that maize straw amendment can moderate the PE promoted by N fertilization. There was a positive linear correlation between the cumulative PE and the input of maize straw C. An increase in maize straw incorporation with N fertilization caused the largest increase in total SOC content at the end of 224-day incubation (the highest 23.7% for C5N2 treatment, i.e., 5× maize straw yield+600kgNha−1a−1). Our findings highlight that in intensively managed agricultural regions, integrating N fertilization with crop residue amendment can promote SOC sequestration and the retention of fertilizer N in the soil. The results are particularly relevant for developing new or improved farming methods in areas with calcareous soils, such as northern China.

Simulating the effects of long-term discontinuous and continuous fertilization with straw return on crop yields and soil organic carbon dynamics using the DNDC model

The objectives of this study were to investigate the applicability of the DNDC model under long-term discontinuous fertilization (three years of fertilization followed by three years of no fertilization) in the winter wheat-summer maize rotation cropping system, and to analyze the effects of long-term fertilization and straw return on soil organic carbon (SOC) and crop yields and to optimize the ratio of straw incorporation to fertilization rate. A 30-year (1981–2011) long-term experiment was conducted at the Hengshui ExperimentalStation in Hebei Province with combinations of four inorganic fertilization rates and four maize straw incorporation amounts. Crop yields and SOC contents in the topsoil (0–20cm) were measured for each treatment, and the data were used to calibrate and validate the DNDC model. Resultsindicated the good performance of DNDC model in simulating crop yields and SOC contents with modeling efficiency ≥0.55, normalized root mean square error ≤31.3%, and index of agreement ≥0.85. However, the model performed relatively poorly in four treatments without fertilizers. Determination coefficients between simulated and measured values of the winter wheat yields, summer maize yields, and SOC contents were 0.747, 0.671, and 0.425, respectively. Crop yield and SOC content predictions were better during periods with fertilization than that during periods without fertilization. The rate of increase in crop yields induced by increasing fertilization rates was higher than that induced by increasing amounts of incorporated straw. However, rate of increase in SOC content resulting from increasing fertilization rate was lower than that from increasing amount of incorporated straw. Over 52 scenarios combining 13 levels of fertilizer rates with four levels of maize straw incorporation were simulated. Resultsfrom yields, soil fertility, and greenhouse gas emission showed that the optimal ratio for discontinuous fertilization was 420kgNha−1yr−1 combined with straw incorporation of 10000kgha−1yr−1, whereas that for continuous fertilization was 300kgNha−1yr−1 combined with straw incorporation of 10000kgha−1yr−1. Thus, the DNDC model could effectively predict crop yields and SOC dynamics under discontinuous fertilization conditions in Hengshui. High and stable crop yields and enhanced soil fertility could be achieved by optimizing the ratio of fertilization rate to amount of incorporated straw.

Effects of Straw Incorporation on Soil Nutrients, Enzymes, and Aggregate Stability in Tobacco Fields of China

To determine the effects of straw incorporation on soil nutrients, enzyme activity, and aggregates in tobacco fields, we conducted experiments with different amounts of wheat and maize straw in Zhucheng area of southeast Shandong province for three years (2010–2012). In the final year of experiment (2012), straw incorporation increased soil organic carbon (SOC) and related parameters, and improved soil enzyme activity proportionally with the amount of straw added, except for catalase when maize straw was used. And maize straw incorporation was more effective than wheat straw in the tobacco field. The percentage of aggregates &gt;2 mm increased with straw incorporation when measured by either dry or wet sieving. The mean weight diameter (MWD) and geometric mean diameter (GMD) in straw incorporation treatments were higher than those in the no-straw control (CK). Maize straw increased soil aggregate stability more than wheat straw with the same incorporation amount. Alkaline phosphatase was significantly and negatively correlated with soil pH. Sucrase and urease were both significantly and positively correlated with soil alkali-hydrolysable N. Catalase was significantly but negatively correlated with soil extractable K (EK). The MWD and GMD by dry sieving had significantly positive correlations with SOC, total N, total K, and EK, but only significantly correlated with EK by wet sieving. Therefore, soil nutrients, metabolic enzyme activity, and aggregate stability might be increased by increasing the SOC content through the maize or wheat straw incorporation. Moreover, incorporation of maize straw at 7500 kg·hm−2 was the best choice to enhance soil fertility in the tobacco area of Eastern China.

EFFECT OF NITROGEN FERTILIZER AND MAIZE STRAW INCORPORATION ON NH4+15N AND N0(3) -15N ACCUMULATION IN BLACK SOIL OF NORTHEAST CHINA AMONG THREE CONSECUTIVE CROPPING CYCLES

ABSTRACT A pot experiment was conducted to evaluate the effect of nitrogen (N) fertilizer and maize straw incorporation on the accumulation of NH 4+ - 15 N and NO 3- - N in soil inorganic N pool among three consecutive cropping cycles, aimed to search for an effective N management practice to decrease superfluous accumulation of soil inorganic N and fertilizer N losses. The results showed that the amounts of soil NH 4+ - 15 N, NO 3- - 15 N and inorganic 15 N, and their percent to applied 15 N-labeled fertilizer declined significantly with sampling time ( p ≤ 0.001). Compared to low N application rate (44.64 mg N kg -1 soil), high N application rate (89.28 mg N kg soil) enhanced significantly the amounts of soil NH 4+ - 15 N, NO 3- - N and inorganic 15 N by 238.6%, 132.9% and 197.3%, respectively ( p ≤ 0.001). In contrast, maize straw addition declined significantly the amounts of soil NH 4+ - 15 N and inorganic 15 N by 21.4% and 16.1% compared to without maize straw ( p ≤ 0.001). The results suggested that a combined application of chemical fertilizer and maize straw with a wide C/N ratio is an important means for reducing the superfluous accumulation of fertilizer N as soil inorganic N to subsequently lower its loss.

Dynamics of benazolin under the influence of degrading maize straw in undisturbed soil columns

The effect of organic carbon amendment on the fate of benazolin was investigated in undisturbed soil columns. The soil columns were obtained from three different soil types located in three different regions with different crop production regimes. All soils were operated in a normal crop production regime, and one of the soils was additionally operated in low and high crop production regimes. Two experimental setups were conducted, one using [(14)C]maize straw and nonlabeled benazolin and one using nonlabeled maize straw and [(14)C]benazolin. The column experiments with [(14)C]maize straw showed that the residual crop residues remained mainly in the top layer. Benazolin and its metabolites showed a higher retention in columns that were amended with maize straw compared to column without amendment. The production regimes of the soils did not influence the behavior of benazolin. The effect of maize straw incorporation on the translocation and degradation of benazolin could well be caused by a change in the soil microbial activity, leading to an enhanced degradation of benazolin and producing metabolites exhibiting a sorption behavior different from the parent.