Nitrogen use efficiency of cotton (Gossypium hirsutum L.) as influenced by wheat–cotton cropping systems

Wheat–cotton rotations largely increase crop yield and improve resources use efficiency, such as the radiation use efficiency. However, little information is available on the nitrogen (N) utilization and requirement of cotton under wheat–cotton rotations. This study was to determine the N uptake and use efficiency by evaluating the cotton (Gossypium hirsutum L.) N use and the soil N balances, which will help to improve N resource management in wheat–cotton rotations. Field experiments were conducted during 2011/2012 and 2012/2013 growing seasons in the Yangtze River region in China. Two cotton cultivars (Siza 3, mid-late maturity with 130 days growth duration; CCRI 50, early maturity with 110 days growth duration) were planted under four cropping systems including monoculture cotton (MC), wheat/intercropped cotton (W/IC), wheat/transplanted cotton (W/TC) and wheat/direct-seeded cotton (W/DC). The N uptake and use efficiency of cotton were quantified under different cropping systems. The results showed that wheat–cotton rotations decreased the cotton N uptake through reducing the N accumulation rate and shortening the duration of fast N accumulation phase as compared to the monoculture cotton. Compared with MC, the N uptake of IC, TC and DC were decreased by 12.0%, 20.5% and 23.4% for Siza 3, respectively, and 7.3%, 10.7% and 17.6% for CCRI 50, respectively. Wheat–cotton rotations had a lower N harvest index as a consequence of the weaker sink capacity in the cotton plant caused by the delayed fruiting and boll formation. Wheat–cotton rotations used N inefficiently relative to the monoculture cotton, showing consistently lower level of the N agronomic use efficiency (NAE), N apparent recovery efficiency (NRE), N physiological efficiency (NPE) and N partial factor productivity (NPFP), particularly for DC. Relative to the mid–late maturity cultivar of Siza 3, the early maturity cultivar of CCRI 50 had higher N use efficiency in wheat–cotton rotations. An analysis of the crop N balance suggested that the high N excess in preceding wheat (Triticum aestivum L.) in wheat–cotton rotations led to significantly higher N surpluses than the monoculture cotton. The N management for the cotton in wheat–cotton rotations should be improved by means of reducing the base fertilizer input and increasing the bloom application.     

Increasing connectivity in fragmented landscapes: An investigation of evidence for biodiversity gain in woodlands

Increasing connectivity is frequently proposed as an effective strategy to address biodiversity decline within fragmented habitats. Woodland habitats in Great Britain have been significantly reduced in area and are described as having ‘fragmented’ distribution. Many researchers have associated declines in woodland species with fragmentation. Currently, there is a concerted effort to increase connectivity (through increasing the number of physical links) between woodlands, often through the development of habitat networks, with the aim of increasing biodiversity. This aim is driven through rising interest in the role of landscape scale processes in biodiversity conservation and increasing concern of the fate of populations facing a predicted increase in habitat isolation through climate change.In this paper, the evidence behind the assumption that increasing connectivity will increase biodiversity is reviewed, together with the assumptions made during development of models that identify potential networks within which connectivity is to be increased. Gaps identified within the evidence base lead to the suggestion of new research areas that will provide a firm basis from which more informed evaluation of increasing connectivity for biodiversity gain can be developed. Alternative approaches to enhancing woodland biodiversity in fragmented landscapes are proposed.     

Effect of Key Priority Forestry Programs on off-farm employment: Evidence from Chinese rural households

This paper examines how 3 Key Priority Forestry Programs (the KPFPs) influenced rural off-farm employment time using a long-term panel dataset that spans 18 years (1995–2012) and includes 6 provinces in China. The programs included the most significant forest policies, including the Sloping Land Conversion Program (SLCP), Desertification Combating Program around Beijing and Tianjin (DCBT), and Natural Forest Protection Program (NFPP). A labor supply model with both fixed and cluster effects were used to identify the programs' disparate impacts in the different regions and on various policy stages. We found the following results: (i) the overall effect of the SLCP was pronounced in relation to the off-farm participation time, but it weakened gradually after the first policy stage; (ii) the DCBT had less impact than the SLCP in increasing the work time of farmers who already had off-farm jobs, but it was better than the SLCP during the various subsidy policy stages; (iii) the NFPP's total effect was insignificant; (iv) forestry subsidies tended to be decoupled for farmers in China, since the substitution effect was greater than the income effect and increased the supply of non-agricultural labor hours. The researches and policy implications of our work are also discussed here.     

Modeling height-diameter relationship for artificial monoculture Metasequoia glyptostroboides in sub-tropic coastal megacity Shanghai,China

Tree height is a key variable in forest monitoring studies and for forest management. However, tree height measurement is time consuming, and the recommended procedure is to use estimates from tree height (H) - diameter at breast height (DBH) models. Increasingly, H-DBH models are being developed for urban forests, providing tools to forest management and ecosystem services estimation. Here, we compared model forms and approaches for predicting H as a function of DBH and additional stand level covariates variables. Four model forms were evaluated: (i) basic models (which only used DBH as predictor variable); (ii) generalized models (which used DBH and other predictor variables based on the best basic model); (iii) a mixed-effects model based on the best basic model; and (iv) a mixed-effects model based on the generalized model. Several sampling designs aimed at minimizing height measurement were tested in terms of accuracy and applicability. Taking predicted accuracy and investigation cost into account, we recommend generalized non-linear mixed-effects model (NLME) when there were two or less tree height measurements taken in a given stand. The basic NLME model could be calibrated when there were 3 or more tree height measurements, depending on the required level of accuracy and investigation cost. Additionally, we first reported that soil pH as a covariate variable in H-DBH model and our generalized NLME model implied that the difference in the H-DBH relationship caused by pH varies among different stands. This finding may be attributable to differing biological properties of the similar alkaline tolerance species.     

植物根围促生细菌菌剂增强玉米干旱耐受性研究

选用植物根围促生细菌(PGPR)菌剂BBS处理玉米幼苗,研究干旱胁迫下玉米幼苗叶片相关生理特性及基因表达差异。结果表明,干旱胁迫15 d后,BBS处理组玉米幼苗的萎蔫程度显著低于对照组;处理组植株叶片MDA含量仅为对照组的74.35%,叶片脯氨酸和可溶性糖含量分别是对照组的3.39倍和1.07倍;处理组植株叶片ZmP5CS1的表达水平及SOD活性均显著高于对照组;BBS处理组植株叶片在干旱胁迫过程中一直保持较低的H_2O_2含量。研究得出,BBS处理能够有效减缓干旱胁迫对玉米幼苗造成的伤害,进而加速正常浇水后的恢复。处理组植株叶片NCED1和ZmDREB2.7的高水平表达也表明干旱胁迫下玉米幼苗与BBS的互作过程可能有依赖ABA信号途径及不依赖ABA信号途径的共同参与。     

A comparison of soil-water distribution under ridge and bed cultivated potatoes

Data is presented comparing infiltration of irrigation and rain water to potato crops planted in ridges and beds in East Anglia, UK. An automatic soil water station (ASWS) was used to monitor soil water content and potential in the two cultivation systems. The ASWS data indicated that most of the water bypassed the potatoes planted in ridges as irrigation water applied to the crop from a boom irrigator was shed off the ridges infiltrating in the furrows. This was due to the water repellent nature of the sandy soil and meant that the irrigation water bypassed the potatoes. A soil water deficit built up in the core of the ridge as the crop grew and was not replenished by irrigations. A second early potato crop planted in beds was more successful at capturing water as the flat bed increased water infiltration around the crop. This has major implications for cultivation practice, scab control and crop water management. Instruments measuring soil water potential, content, temperature and rainfall were connected to a data logger powered by a solar panel and proved a successful way of monitoring infiltration. Hourly data was collected so that a high temporal resolution data set could be constructed in order to increase conceptual understanding of hydrological processes at a scale appropriate to the crop.     

Cis- and trans-protopinium,a novel nematicide,for the eco-friendly management of root-knot nematodes

Plant-derived nematicides are being increasingly used while select synthetic nematicides are phased out for environmental concerns. This is the first report on the in vitro nematicidal activity of cis- and trans-protopinium isolated from roots of Fumaria parviflora and its in vivo effect on the southern root-knot nematode Meloidogyne incognita. Cis- and trans-protopinium was isolated from the methanolic fraction FM2.1, and its structure elucidated using ¹³C and ¹H nuclear magnetic resonance (NMR). The NMR spectra were characterized using deuterated dimethyl sulfoxide (DMSO) at temperatures of 25 and 80 °C. In an in vitro study, over 120 h of incubation, the area under cumulative percent hatch inhibition and mortality of cis- and trans-protopinium reached 100% at a concentration of 200 μg mL⁻¹. In the greenhouse and field settings, cis- and trans-protopinium was evaluated against M. incognita on tomato at a concentration of 100, 200, and 300 μg mL⁻¹ for two consecutive seasons, that is, spring and autumn, in 2010. At a concentration of 300 μg mL⁻¹ in the greenhouse and field trials during spring and autumn, cis- and trans-protopinium significantly reduced the nematode galling index, the number of females per gram of root, and the reproduction factor, as well as increased plant height, fresh and dry shoot weights, and root length. Therefore, cis- and trans-protopinium can be used as an effective and safe nematicide against M. incognita on tomato in an organic and sustainable agricultural production system. Phytochemicals have various agricultural applications, especially to control economically important nematode pests.     

High level of metaflumizone resistance and multiple insecticide resistance in field populations of Spodoptera exigua (Lepidoptera: Noctuidae) in Guangdong Province,China

Spodoptera exigua is a phytophagous pest that causes critical economic losses in vegetable crops, and insecticides are commonly used against it in vegetable growing areas. However, excessive and frequent applications of insecticides cause resistance in S. exigua. The current resistance in field populations of S. exigua collected from Huizhou, Guangdong Province, China to 12 insecticides was investigated. S. exiguahad developed very high resistance to lambda cyhalothrin (2925- to 3449-fold), chlorpyrifos (>1786-fold), emamectin benzoate (174- to 867-fold), and metaflumizone (60.3- to 942-fold). High resistance to tebufenozide (51.5- to 75.4-fold) and chlorfluazuron (60.4- to 63.0-fold) was also found. Synergism assays revealed that the resistance to metaflumizone and lambda cyhalothrin was associated with esterase and microsomal oxidases, respectively. The resistance to emamectin benzoate was not affected by detoxification enzymes inhibitors and might be conferred by other mechanisms. The selection of the field population by metaflumizone for 10generations in the laboratory resulted in a 6.1-fold increase in metaflumizone resistance but did not lead to increases in resistance to other insecticides. After metaflumizone selection, susceptibilities to spinosad and endosulfan did not change, and the susceptibilities to indoxacarb, methomyl, pyridalyl, tebufenozide, chlorfluazuron, emamectin benzoate and lambda cyhalothrin decreased slightly. However, no statistically significant differences in the resistance levels were observed among the selected population, its starting strain and the unselected strain. The resistance to chlorantraniliprole noticeably decreased in unselected strain and the strain subjected to selection for 10 generations compared with their starting strains. Lack of cross-resistance to tested insecticides suggested the involvement of multiple mechanisms of resistance and the need for wise application of these insecticides for the management of S. exigua.     

Chemical composition of organic matter in a deep soil changed with a positive priming effect due to glucose addition as investigated by 13C NMR spectroscopy

Fresh organic carbon becomes more accessible to deep soil following losses of surface soil and deep intentional incorporation of crop residues, which can cause the priming effect and influence the quality and quantity of SOC in deep soil. This study determined the priming effect due to addition of water-dissolved ¹³C-labeled glucose (0.4 g C kg⁻¹ soil) to a soil taken from 1.00 to 1.20 m depth. The changes in chemical compositions of SOC in soils without (G₀) and with (G_0.4) glucose addition during a 31-d incubation were investigated with solid-state ¹³C cross polarization/total sideband suppression (¹³C-CP/TOSS) and CP/TOSS with dipolar dephasing nuclear magnetic resonance (NMR) techniques. No glucose remained in the soil after 21 days of incubation, with 48% being completely mineralized into CO₂ emission and 52% being incorporated into SOC. The native SOC was decomposed by 0.23% more in G_0.4 than in G₀. The NMR spectra demonstrated that both labile and recalcitrant organic compounds in SOC changed during the incubation, but in different manners in G₀ and G_0.4. During the incubation, the -(CH₂)_n-abundance in G₀ did not change over time, but in G_0.4 it decreased from Day 0 to Day 21 and then increased from Day 21 to Day 31, suggesting shifts of soil microbial communities only in G_0.4. After the incubation, in G₀ the abundances of ketones/aldehydes and nonpolar alkyl C increased, but those of aromatic C–C and protonated O-alkyl C (OCH) decreased; In G_0.4, the abundances of NCH and protonated O-alkyl C (OCH) increased, but those of nonpolar alkyl C and nonprotonated aromatic C–O and ketones/aldehydes decreased. Such inconsistent changes in recalcitrant compounds between G₀ and G_0.4 indicated that glucose addition likely primed the decomposition of aromatic C–O and suppressed the formation of ketones/aldehydes. We have demonstrated for the first time that the priming effect of SOC decomposition in the deep soil was involved with larger notable changes in both labile and recalcitrant structures of native SOC due to glucose addition compared with that without glucose addition.