Benhua Sun

Impact of soil tillage on the robustness of the genetic component of variation in phosphorus (P) use efficiency in barley ( Hordeum vulgare L.)

To enhance the sustainability of agriculture it is imperative that the use of P-fertilisers by temperate cereal crops be improved. This can be achieved both by agronomic and genetic approaches. While many studies have demonstrated genotypic variation in P-use efficiency in a number of cereal species the robustness of this genetic variation in contrasting environments is rarely considered. In this paper we describe an experiment in which we compare the P-nutrition of winter and spring barley genotypes from an association genetic-mapping population grown in a field trial with different cultivation treatments (conventional plough vs. minimum tillage) which had been established over a number of years. We demonstrate that, while there is significant variation between genotypes in their P nutrition, this variation is not comparable between cultivation treatments and only one winter barley genotype (cv. Gleam) has beneficial P-use efficiency traits in both cultivation systems. Analysis of the association genetic-mapping population demonstrated that there was a strong environmental component in the genotypic variation, with more significant associations of shoot P concentration with known SNP (Single Nucleotide Polymorphism) markers when the population was grown in minimum tillage treatments. These data suggest that it may be possible to identify genetic components to variation in P nutrition in barley, but that a large interaction with environmental variables may limit the usefulness of any genes or markers discovered for improving P-use efficiency to the conditions under which the screening was performed.

Contribution of Atmospheric Nitrogen Compounds to N Deposition in a Broadleaf Forest of Southern China

A one-year study in a typical red soil region of southern China was conducted to determine atmospheric nitrogen (N) fluxes of typical N compounds (NH3, NH4-N, NO3-N, and NO2) and contribution of three sources (gas, rainwater, and particles) to N deposition. From July 2003 to June 2004, the total atmospheric N deposition was 70.7 kg N ha^(-1), with dry deposition accounting for 75% of the total deposition. Dry NH3 deposition accounted for 73% of the dry deposition and 55% of the total deposition. Moreover, NO2 contributed 11% of the dry deposition and 8% of the total deposition. Reduced N compounds (NH(superscript + subscript 4) and NH3) were the predominate contributors, accounting for 66% of the total deposition. Therefore, atmospheric N deposition should be considered when soil acidification and critical loads of atmospheric deposition on soils are estimated.

Effects of straw and plastic film mulching on greenhouse gas emissions in Loess Plateau, China: A field study of 2 consecutive wheat-maize rotation cycles

Mulching practices have long been used to modify the soil temperature and moisture conditions and thus potentially improve crop production in dryland agriculture, but few studies have focused on mulching effects on soil gaseous emissions. We monitored annual greenhouse gas (GHG) emissions under the regime of straw and plastic film mulching using a closed chamber method on a typical winter-wheat (Triticum aestivum L. cv Xiaoyan 22) and summer-maize (Zea mays L. cv Qinlong 11) rotation field over two-year period in the Loess Plateau, northwestern China. The following four field treatments were included: T1 (control, no mulching), T2 (4000kgha-1 wheat straw mulching, covering 100% of soil surface), T3 (half plastic film mulching, covering 50% of soil surface), and T4 (complete plastic film mulching, covering 100% of soil surface). Compared with the control, straw mulching decreased soil temperature and increased soil moisture, whereas plastic film mulching increased both soil temperature and moisture. Accordingly, straw mulching increased annual crop yields over both cycles, while plastic film mulching significantly enhanced annual crop yield over cycle 2. Compared to the no-mulching treatment, all mulching treatments increased soil CO2 emission over both cycles, and straw mulching increased soil CH4 absorption over both cycles, but patterns of soil N2O emissions under straw or film mulching are not consistent. Overall, compared to T1, annual GHG intensity was significantly decreased by 106%, 24% and 26% under T2, T3 and T4 over cycle 1, respectively; and by 20%, 51% and 29% under T2, T3 and T4 over cycle 2, respectively. Considering the additional cost and environmental issues associated with plastic film mulching, the application of straw mulching might achieve a balance between food security and GHG emissions in the Chinese Loess Plateau. However, further research is required to investigate the perennial influence of different mulching applications.

Assessment of climate change impacts on soil organic carbon and crop yield based on long-term fertilization applications in Loess Plateau, China

Background and AimsClimate change may significantly impact crop yields and soil. In this study the DNDC model, together with climatic outputs from Hadley Centre’s general circulation model (HadCM3), was used to investigate the influence of projected climate change and management practices on soil organic carbon (SOC) dynamics and crop yield of the Chinese Loess Plateau. The results identify management practices with the greatest potential to mitigate climate change and to increase SOC in this area.MethodsField experiments on winter-wheat (Triticum aestivum L.) and summer maize (Zea mays L.) rotation included a control and four types of fertilization treatments: T1 (control), T2 (inorganic fertilizer), T3 (NPK inorganic fertilization combined with wheat or maize residue return), T4 (NPK inorganic fertilization combined with low amount of manure) and T5 (NPK inorganic fertilization combined with high amount of manure). DNDC model was calibrated using the field data from 1991 to 2000 and validated from 2001 to 2010. Furthermore, a baseline climate and three future climate scenarios (A1B, A2 and B1) were considered.ResultsDNDC model effectively simulated the SOC and crop yields. The findings showed that in 1991–2010, T1 maintained its initial SOC level but reduced crop yields, while T2 promoted crop production with less effect on soil carbon storage. However, T3, T4 and T5 enhanced both crop yield and soil carbon, and the best results were observed under T5. The investigated climate scenarios substantially affect SOC content and crop yields. In terms of SOC content, B1 had great effects on T1, T4 and T5, while A1B on T2 and T3. Considering crop yields, in all treatments, the trends are B1 > A1B > A2 for winter-wheat and A2 > A1B > B1 for summer maize, respectively.ConclusionsThe impacts of climate changes on SOC dynamics and crop yields were different depending on the management applied. Thus, the adoption of certain management practices in the Chinese Loess Plateau agroecosystems could be critical in maximizing SOC sequestration and reducing CO2 in the atmosphere. Reasonably low temperature and high precipitation can enhance winter-wheat yields, while maize yields need medium temperature and precipitation. We recommended the combined application of inorganic and organic fertilizers to achieve a balance between food security and soil carbon sequestration objectives.

Trends of Yield and Soil Fertility in a Long-Term Wheat-Maize System

The sustainability of the wheat-maize rotation is important to Chinas food security. Intensive cropping without recycling crop residues or other organic inputs results in the loss of soil organic matter (SOM) and nutrients, and is assumed to be non-sustainable. We evaluated the effects of nine different treatments on yields, nitrogen use efficiency, P and K balances, and soil fertility in a wheat-maize rotation system (1991–2010) on silt clay loam in Shaanxi, China. The treatments involved the application of recommended dose of nitrogen (N), nitrogen and phosphorus (NP), nitrogen and potassium (NK), phosphorus and potassium (PK), combined NPK, wheat or maize straw (S) with NPK (SNPK), or dairy manure (M) with NPK (M1NPK and M2NPK), along with an un-treated control treatment (CK). The mean yields of wheat and maize ranged from 992 and 2 235 kg ha−1 under CK to 5 962 and 6 894 kg ha−1 under M2NPK treatment, respectively. Treatments in which either N or P was omitted (N, NK and PK) gave significantly lower crop yields than those in which both were applied. The crop yields obtained under NP, NPK and SNPK treatments were statistically identical, as were those obtained under SNPK and MNPK. However, M2NPK gave a significant higher wheat yield than NP, and MNPK gave significant higher maize yield than both NP and NPK. Wheat yields increased significantly (by 86 to 155 kg ha−1 yr−1) in treatments where NP was applied, but maize yields did not. In general, the nitrogen use efficiency of wheat was the highest under the NP and NPK treatments; for maize, it was the highest under MNPK treatment. The P balance was highly positive under MNPK treatment, increasing by 136 to 213 kg ha−1 annually. While the K balance was negative in most treatments, ranging from 31 to 217 kg ha−1 yr−1, levels of soil available K remained unchanged or increased over the 20 yr. SOM levels increased significantly in all treatments. Overall, the results indicated that combinations of organic manure and inorganic nitrogen, or returning straw with NP is likely to improve soil fertility, increasing the yields achievable with wheat-maize system in a way which is environmentally and agronomically beneficial on the tested soil.

Soil aggregation and aggregate associated organic carbon and total nitrogen under long-term contrasting soil management regimes in loess soil

Abstract This study investigated the effects of three contrasting soil management regimes and different nutrient treatments on the distribution of water-stable aggregates (>2, 1–2, 0.5–1, 0.25–0.5, and 0.25 mm) and mean weight diameter (MWD) at 0–10 and 10–20 cm soil horizons compared with Cropping, whereas Fallow yielded lower values of above two parameters. Abandonment increased SOC and TN contents in all aggregate sizes by 17–62% and 6–60%, respectively, at 0–10 cm soil layer compared with Cropping. Conversely, Fallow decreased SOC and TN contents in all aggregates by 7–27% and 7–25%, respectively. Nevertheless, the three soil management regimes presented similar SOC contents in all aggregates at 10–20 cm soil horizon. Only Cropping showed higher TN content in >0.5 mm aggregates than the two other regimes. Consequently, Abandonment enhanced the partitioning proportions of SOC and TN in >1 mm macro-aggregates, and Fallow promoted these proportions in micro-aggregates compared with Cropping. Under Cropping, long-term fertilization did not affect the distribution of aggregates and MWD values compared with those under CK, except for NPK treatment. Fertilizer treatments enhanced SOC and TN contents in aggregates at all tested soil depths. However, fertilization did not affect the partitioning proportions of SOC and TN contents in all aggregates compared with CK. Comprehensive results showed that different soil management regimes generated varied patterns of SOC and TN sequestration in loess soil. Abandonment enhanced soil aggregation and sequestered high amounts of SOC and TN in macro-aggregates. Long-term amendment of organic manure integrated with NPK maintained soil aggregate stability and improved SOC and TN sequestration in all aggregates in loess soil subjected to dryland farming.

Microbial Properties of a Loess Soil as Affected by Various Nutrient Management Practices in the Loess Plateau of China

Microbial biomass phosphorus (MBP) and its relationships with other biological and chemical properties were studied on loess soil with an 11-year long-term fertilization experiment. The results indicated that inorganic fertilizers (F) improved soil microbial biomass carbon (MBC), nitrogen (MBN), and MBP levels and F plus maize stalk (SNPK) improved MBC and MBN. Manuring markedly increased soil MBC, MBN, and MBP levels. Fertilization decreased the ratios of MBC/MBN, MBC/MBP, and MBN/MBP. Microbial biomass phosphorus was positively and linearly correlated with MBC, MBN, organic carbon (SOC), total phosphorus (TP), water-soluble P, and Olsen P but negatively correlated with soil pH. Microbial biomass phosphorus constituted 2% of TP on control (CK) and inorganic fertilizer treatments and 12% on manure plots. Microbial biomass phosphorus to Olsen P ratios were 50% on CK, F, and SNPK and 80% on manure treatments. Measurements of MBP in soil containing high Olsen P were subject to analytical problems of unknown reasons.