Combined application of chemical fertilizers with organic amendments was recommended as a strategy for improving yield, soil carbon storage, and nutrient use efficiency.  However, how the long-term substitution of chemical fertilizer with organic manure affects rice yield, carbon sequestration rate (CSR), and nitrogen use efficiency (NUE) while ensuring environmental safety remains unclear.  This study assessed the long-term effect of substituting chemical fertilizer with organic manure on rice yield, CSR, and NUE.  It also determined the optimum substitution ratio in the acidic soil of southern China.  The treatments were: (i) NPK₀, unfertilized control; (ii) NPK₁, 100% chemical nitrogen, phosphorus, and potassium fertilizer; (iii) NPKM₁, 70% chemical NPK fertilizer and 30% organic manure; (iv) NPKM₂, 50% chemical NPK fertilizer and 50% organic manure; and (v) NPKM₃, 30% chemical NPK fertilizer and 70% organic manure.  Milk vetch and pig manure were sources of manure for early and late rice seasons, respectively.  The result showed that SOC content was higher in NPKM₁, NPKM₂, and NPKM₃ treatments than in NPK₀ and NPK₁ treatments.  The carbon sequestration rate increased by 140, 160, and 280% under NPKM₁, NPKM₂, and NPKM₃ treatments, respectively, compared to NPK₁ treatment.  Grain yield was 86.1, 93.1, 93.6, and 96.5% higher under NPK₁, NPKM₁, NPKM₂, and NPKM₃ treatments, respectively, compared to NPK₀ treatment.  The NUE in NPKM₁, NPKM₂, and NPKM₃ treatments was higher as compared to NPK₁ treatment for both rice seasons.  Redundancy analysis revealed close positive relationships of CSR with C input, total N, soil C:N ratio, catalase, and humic acids, whereas NUE was closely related to grain yield, grain N content, and phenol oxidase.  Furthermore, CSR and NUE negatively correlated with humin acid and soil C:P and N:P ratios.  The technique for order of preference by similarity to ideal solution (TOPSIS) showed that NPKM₃ treatment was the optimum strategy for improving CSR and NUE.  Therefore, substituting 70% of chemical fertilizer with organic manure could be the best management option for increasing CSR and NUE in the paddy fields of southern China

 

该研究系统阐述了长期不同施肥对土壤剖面SOC和N库的影响，通过冗余分析了SOC团聚体组分及影响因素，三维表面分析深入理解剖面SOC和N库对作物产量的影响。与化肥处理相比，长期施用有机肥通过增加表土层 (0–20 cm）SOC输入、SOC储量、TN储量和土壤pH值来提高作物产量。不同施肥处理的SOC团聚体组分存在差异，所有处理SOC团聚体组分高低依次为矿物结合有机碳（mSOC）>粗自由颗粒有机碳（cfPOC）>物理保护有机碳（iPOC）>细自由颗粒有机碳（ffPOC）。施用有机肥处理的所有SOC组分含量均显著高于化肥处理。在不同SOC团聚体组分中，ffPOC对不同施肥处理的敏感性最高。单施有机肥（M）和有机无机肥配施（NPKM）显著提高了表层（0-20 cm）SOC和TN含量，与化肥处理相比，M和NPKM处理降低了深层土壤（80-100 cm）中的SOC和N含量，有利于减少养分垂直流动，从而减少养分的淋溶损失。

大豆是典型的短日照作物，对光周期的敏感性决定大豆品种的适宜种植区域。在光周期调控的大豆开花途径中，开花抑制因子E1起主导作用。E1La和E1Lb是E1的同源基因，功能与E1类似。本研究利用RNA干扰（RNAi）技术在大豆品种自贡冬豆中同时沉默了E1和E1La/b基因。结果显示，与受体品种自贡冬豆相比，RNAi株系开花期和成熟期大幅度提前，光周期敏感性明显下降。在RNAi超早熟株系中，开花抑制基因GmFT4的表达水平显著下降，而开花促进基因GmFT2a/GmFT5a的表达水平明显上升。生育期组鉴定结果显示，自贡冬豆的生育期组属于MG VIII，为极晚熟品种，而RNAi株系的生育期组为MG 000，属超早熟新种质，可在中国最北部（53.5°N）的漠河市北极村种植。本研究验证了E1和E1La/b对大豆开花期和成熟期的负调控作用，创制出超早熟大豆新材料，为显著钝化大豆品种的光周期敏感性，大幅度缩短生育期，实现南方大豆种质资源在北方大豆主产区的有效利用，拓宽高寒地区大豆的遗传基础提供了新的途径。

Soil productivity (SP) without external fertilization influence is an important indicator for the capacity of a soil to support crop yield. However, there have been difficulties in estimating values of SPs for soils after various long-term field treatments because the treatment without external fertilization is used but is depleted in soil nutrients, leading to erroneous estimation. The objectives of this study were to estimate the change of SP across different cropping seasons using pot experiments, and to evaluate the steady SP value (which is defined by the basal contribution of soil itself to crop yield) after various longterm fertilization treatments in soils at different geographical locations. The pot experiments were conducted in Jinxian of Jiangxi Province with paddy soil, Zhengzhou of Henan Province with fluvo-aquic soil, and Gongzhuling of Jilin Province with black soils, China. Soils were collected after long-term field fertilization treatments of no fertilizer (control; CK-F), chemical fertilizer (NPK-F), and combined chemical fertilizer with manure (NPKM-F). The soils received either no fertilizer (F0) or chemical fertilizer (F1) for 3–6 cropping seasons in pots, which include CK-P (control; no fertilizer from long-term field experiments for pot experiments), NPK-P (chemical fertilizer from long-term field experiments for pot experiments), and NPKM-P (combined chemical and organic fertilizers from long-term field experiments for pot experiments). The yield data were used to calculate SP values. The initial SP values were high, but decreased rapidly until a relatively steady SP was achieved at or after about three cropping seasons for paddy and fluvo-aquic soils. The steady SP values in the third cropping season from CK-P, NPK-P, and NPKM-P treatments were 37.7, 44.1, and 50.0% in the paddy soil, 34.2, 38.1, and 50.0% in the fluvo-aquic soil, with the highest value observed in the NPKM-P treatment for all soils. However, further research is required in the black soils to incorporate more than three cropping seasons. The partial least squares path mode (PLS-PM) showed that total N (nitrogen) and C/N ratio (the ratio of soil organic carbon and total N) had positive effects on the steady SP for all three soils. These findings confirm the significance of the incorporation of manure for attaining high soil productivity. Regulation of the soil C/N ratio was the other main factor for steady SP through fertilization management.

As an important food crop and oil crop, soybean (Glycine max [L.] Merr.) is capable of nitrogen-fixing by root nodule.  Previous studies showed that GmNMH7, a transcription factor of MADS-box family, is associated with nodule development, but its specific function remained unknown.  In this study, we found that GmNMH7 was specifically expressed in root and nodule and the expression pattern of GmNMH7 was similar to several genes involved in early development of nodule (GmENOD40-1, GmENOD40-2, GmNFR1a, GmNFR5a, and GmNIN) after rhizobia inoculation.  The earlier expression peak of GmNMH7 compared to the other genes (GmENOD40-1, GmENOD40-2, GmNFR1a, GmNFR5a, and GmNIN) indicated that the gene is related to the nod factor (NF) signaling pathway and functions at the early development of nodule.  Over-expression of GmNMH7 in hairy roots significantly reduced the nodule number and the root length.  In the transgenic hairy roots, over-expression of GmNMH7 significantly down-regulated the expression levels of GmENOD40-1, GmENOD40-2, and GmNFR5α.  Moreover, the expression of GmNMH7 could respond to abscisic acid (ABA) and gibberellin (GA₃) treatment in the root of Zigongdongdou seedlings.  Over-expressing GmNMH7 gene reduced the content of ABA, and increased the content of GA₃ in the positive transgenic hairy roots.  Therefore, we concluded that GmNMH7 might participate in the NF signaling pathway and negatively regulate nodulation probably through regulating the content of GA₃.
 

Intercropping is one of the most vital practice to improve land utilization rate in China that has limited arable land resource. However, the traditional intercropping systems have many disadvantages including illogical field lay-out of crops, low economic value, and labor deficiency, which cannot balance the crop production and agricultural sustainability. In view of this, we developed a novel soybean strip intercropping model using maize as the partner, the regular maize-soybean strip intercropping mainly popularized in northern China and maize-soybean relay-strip intercropping principally extended in southwestern China. Compared to the traditional maize-soybean intercropping systems, the main innovation of field lay-out style in our present intercropping systems is that the distance of two adjacent maize rows are shrunk as a narrow strip, and a strip called wide strip between two adjacent narrow strips is expanded reserving for the growth of two or three rows of soybean plants.  The distance between outer rows of maize and soybean strips are expanded enough for light use efficiency improvement and tractors working in the soybean strips.  Importantly, optimal cultivar screening and increase of plant density achieved a high yield of both the two crops in the intercropping systems and increased land equivalent ratio as high as 2.2.  Annually alternative rotation of the adjacent maize- and soybean-strips increased the grain yield of next seasonal maize, improved the absorption of nitrogen, phosphorus, and potasium of maize, while prevented the continuous cropping obstacles.  Extra soybean production was obtained without affecting maize yield in our strip intercropping systems, which balanced the high crop production and agricultural sustainability.

Soybean (Glycine max (L.) Merr.) is a major crop that provides plant-origin protein and oil for humans and livestock.  Although the soybean vegetative tissues and seeds provide a major source of high-quality protein, they suffer from low concentration of an essential sulfur-containing amino acid, methionine, which significantly limits their nutritional quality.  The level of methionine is mainly controlled by the first unique enzyme of methionine synthesis, cystathione γ-synthase (CGS).  Aiming to elevate methionine level in vegetative tissues and seeds, we constitutively over-expressed a feedback-insensitive
Arabidopsis CGS (AtD-CGS) in soybean cultivars, Zigongdongdou (ZD) and Jilinxiaoli 1 (JX).  The levels of soluble methionine increased remarkably in leaves of transgenic soybeans compared to wild-type plants (6.6- and 7.3-fold in two transgenic ZD lines, and 3.7-fold in one transgenic JX line).  Furthermore, the total methionine contents were significantly increased in seeds of the transgenic ZD lines (1.5- to 4.8-fold increase) and the transgenic JX lines (1.3- to 2.3-fold increase) than in the wild type.  The protein contents of the transgenic soybean seeds were significantly elevated compared to the wild type, suggesting that the scarcity of methionine in soybeans may limit protein accumulation in soybean seeds.  The increased protein content did not alter the profile of major storage proteins in the seeds.  Generally, this study provides a promising strategy to increase the levels of methionine and protein in soybean through the breeding programs.  

Soybean (Glycine max (L.) Merr.) is a typical short-day and warm season plant, and the interval between emergence and flowering has long been known to be regulated by environmental factors, primarily photoperiod and temperature. While the effects of photoperiod and temperature on soybean flowering have been extensively studied, a dissection of the component photo-thermal effects has not been documented for Chinese germplasm. Our objective of the current study was to evaluate the independent- and interactive-photo-thermal responses of 71 cultivars from 6 ecotypes spanning the soybean production regions in China. These cultivars were subjected in pot experiments to different temperature regimes by planting in spring (low temperature (LT)) and summer (high temperature (HT)), and integrating with short day (SD, 12 h), natural day (ND, variable day-length), and long day (LD, 16 h) treatments over two years. The duration of the vegetative phase from emergence to first bloom (R1) was recorded, and the photo-thermal response was calculated. The outcome of this characterization led to the following conclusions: (1) There were significant differences in photo-thermal response among the different ecotypes. High-latitude ecotypes were less sensitive to the independent- and interactive-photo-thermal effects than low-latitude ecotypes; and (2) there was an interaction between photoperiod and temperature, with the effect of photoperiod on thermal sensitivity being greater under the LD than the SD condition, and with the effect of temperature on photoperiodic sensitivity being greater under the LT than the HT condition. The strengths and limitations of this study are discussed in terms of implications for current knowledge and future research directions. The study provides better understanding of photo-thermal effects on flowering in soybean genotypes from different ecotypes throughout China and of the implications for their adaptation more broadly.

Soybean is planted worldwide and its productivity is significantly hampered by salinity. Development of salt tolerant cultivars is necessary for promoting soybean production. Despite wealth of information generated on salt tolerance mechanism, its basics still remain elusive. A continued effort is needed to understand the salt tolerance mechanism in soybean using suitable molecular tools. To better understand the molecular basis of the responses of soybean to salt stress and to get an enrichment of critical salt stress responsive genes in soybean, suppression subtractive hybridization libraries (SSH) are constructed for the root tissue of two cultivated soybean genotypes, one was tolerant and the other was sensitive to salt stress. To compare the responses of plants in salt treatment and non-treatment, SSH1 was constructed for the salt-tolerant cultivar Wenfeng 7 and SSH2 was constructed for the salt-sensitive cultivar Union. From the two SSH cDNA libraries, a total of 379 high quality ESTs were obtained. These ESTs were then annotated by performing sequence similarity searches against the NCBI nr (National Center for Biotechnology Information protein non-redundant) database using the BLASTX program. Sixty-three genes from SSH1 and 49 genes from SSH2 could be assigned putative function. On the other hand, 25 ESTs of SSH1 which may be not the salt tolerance-related genes were removed by comparing and analyzing the ESTs from the two SSH libraries, which increased the proportion of the genes related to salt tolerance in SSH1. These results suggested that the novel way could realize low background of SSH and high level enrichment of target cDNAs to some extent.