Summer maize grain yield and water use efficiency response to straw mulching and plant density

The demand for food security and fresh water due to global warming causes an elevated requirement for food production and water efficiency in the North China Plain (NCP). To establish the optimal summer maize (Zea mays L.) planting schedule, a study was conducted to understand the effects of different straw mulching conditions and plant density on grain yield (GY) and water use efficiency (WUE). During 2012 and 2013 summer maize growing seasons, experiments were conducted with two different mulching treatments, i.e., 0.6 kg m-2 straw mulching (M)and non-mulching (N), and three plant density conditions, i.e., 10.0 plants m-2 (1, high plant density), 7.5 plants m-2 (2, medium plant density), and 5.5 plants m-2 (3, low plant density). The six treatment combinations were: 10.0 plants m-2 density without straw mulching (N1), 10.0 plants m-2 density with 0.6 kg m-2 straw mulching (M1), 7.5plants m-2 density without straw mulching (N2), 7.5 plants m-2 density with 0.6 kg m-2 straw mulching (M2), 5.5 plants m-2 density without straw mulching (N3), and 5.5 plants m-2 density with 0.6 kg m-2 straw mulching (M3). The results showed medium and high plant density treatments had a significant increase in spike number compared tothe low plant density treatment. Straw mulching significantly improved both the GY and WUE of summer maize under low and medium plant density treatments in both dry and normal rainfall years. M2 treatment achieved the highest GY and showed the greatest improvement in WUE of 35.4% over the non-mulching treatment across the three plant densities, and so it will be promoted as an agricultural practice in the NC

Plio-Pleistocene exhumation of the eastern Himalayan syntaxis and its domal ‘pop-up’

The eastern termination of the Himalayan orogen forms a structural syntaxis that is characterised by young (from 10 to < 1 Ma) mineral growth and cooling ages that document Late Miocene to Pleistocene structural, metamorphic, igneous and exhumation events. This region is a steep antiformal and in part domal structure that folds the suture zone between the Indian and Asian plates. It is dissected by the Yarlung Tsangpo, one of the major rivers of the eastern Himalayan–Tibet region, which becomes the Brahmaputra River in the Indian foreland basin before emptying into the Bay of Bengal. Exceptionally high relief and one of the deepest gorges on Earth have developed where the river's tortuous route crosses the Namche Barwa–Gyala Peri massif (> 7 km in elevation) in the core of the syntaxis. Very high erosion rates documented in sediment downstream of the gorge at the foot of the Himalaya contribute ~ 50% of total detritus to the sediment load of the Brahmaputra. The initiation of very high rates of exhumation has been attributed either to the extreme erosive power of a river flowing across a deforming indentor corner and the associated positive feedback, or to the geometry of the Indian plate indentor, with the corner being thrust beneath the Asian plate resulting in buckling which accommodates shortening; both processes may be important. The northern third of the syntaxis corresponds to a steep domal ‘pop-up’ structure bounded by the India–Asia suture on three sides and a thrust zone to the south. Within the dome, Greater Himalaya rocks equilibrated at ~ 800 °C and 25–30 km depth during the Miocene, with these conditions potentially persisting into the latest Miocene and possibly the Pliocene, with modest decompression prior to ~ 4 Ma. This domal ‘pop-up’ corresponds to the area of youngest bedrock ages on a wide variety of thermochronometers and geochronometers. In this paper we review the extensive scientific literature that has focused on the eastern syntaxis and provide new chronological data on its bedrock and erosion products to constrain the age of inception of the very rapid uplift and erosion. We then discuss its cause, with the ultimate aim to reconstruct the exhumation history of the syntaxis and discuss the tectonic context for its genesis. We use zircon and rutile U–Pb, white mica Ar–Ar and zircon fission track dating methods to extract age data from bedrock, Brahmaputra modern sediments (including an extensive compilation of modern detrital chronometry from the eastern Himalaya) and Neogene palaeo-Brahmaputra deposits of the Surma Basin (Bangladesh). Numerical modelling of heat flow and erosion is also used to model the path of rocks from peak metamorphic conditions of ~ 800 °C to < 250 °C. Our new data include U–Pb bedrock rutile ages as young as 1.4 Ma from the Namche Barwa massif and 0.4 Ma from the river downstream of the syntaxis. Combined with existing data, our new data and heat flow modelling show that: i) the detrital age signature of the modern syntaxis is unique within the eastern Himalayan region; ii) the rocks within the domal pop-up were > 575 ± 75 °C only 1–2 Myr ago; iii) the Neogene Surma Basin does not record evidence of the rise and erosion of the domal pop-up until latest Pliocene–Pleistocene time; iv) Pleistocene exhumation of the north-easternmost part of the syntaxis took place at rates of at least 4 km/Myr, with bedrock erosion of 12–21 km during the last 3 Ma; v) the inception of rapid syntaxial exhumation may have started as early as 7 Ma or as late as 3 Ma; and vi) the Yarlung Tsangpo is antecedent and subsequently distorted by the developing antiform. Together our data and modelling demonstrate that the domal pop-up with its exceptional erosion and topographic relief is likely a Pleistocene feature that overprinted earlier structural and metamorphic events typical of Himalayan evolution. Keywords: Eastern Himalayan syntaxis; Namche Barwa; Surma Basin; Yarlung Tsangpo–Brahmaputra; U–Pb rutile dating; Thermal modellin

The complete chloroplast genome of Onosma fuyunensis Y. He & Q.R. Liu and its phylogenetic analysis

The chloroplast genome sequences of Chinese Boraginaceae species, Onosma fuyunensis Y. He & Q.R. Liu, were reported in this study. We sequenced O. fuyunensis using the Illumina HiSeq X Ten platform. The total length of O. fuyunensis chloroplast genome is 150,612 bp, including a large single-copy region of length 82,853 bp, a small single-copy region of length 17,281 bp, and a pair of 25,239-bp inverted repeat regions. The chloroplast genome of O. fuyunensis has 133 genes, including 84 protein-coding, eight ribosomal RNA, and 37 transfer RNA genes. The overall GC content of the whole genome was 43.3%. The phylogenetic analysis revealed that O. fuyunensis is closely related to Borago officinalis and Plagiobothrys nothofulvus

Response of Soil CO 2

Demand for food security and the current global warming situation make high and strict demands on the North China Plain for both food production and the inhibition of agricultural carbon emissions. To explore the most effective way to decrease soil CO2 emissions and maintain high grain yield, studies were conducted during the 2012 and 2013 summer maize growing seasons to assess the effects of wheat straw mulching on the soil CO2 emissions and grain yield of summer maize by adding 0 and 0.6 kg m−2 to fields with plant densities of 100 000, 75 000, and 55 000 plants ha−1. The study indicated that straw mulching had some positive effects on summer maize grain yield by improving the 1000-kernel weight. Meanwhile, straw mulching effectively controlled the soil respiration rate and cumulative CO2 emission flux, particularly in fields planted at a density of 75 000 plants ha−1, which achieved maximum grain yield and minimum carbon emission per unit yield. In addition, soil microbial biomass and microbial activity were significantly higher in mulching treatments than in nonmulching treatments. Consequently, summer maize with straw mulching at 75 000 plants ha−1 is an environmentally friendly option in the North China Plain

Ophiorrhiza reflexa (Rubiaceae), a new species from a karst region in Guangxi, China

Ophiorrhiza reflexa, a new species from Guangxi, China, is described and illustrated in this study. It is morphologically similar to O. alatiflora due to the branched inflorescence, distylous flowers and the tubular-funnelform corolla with five longitudinal wings. The new species can be distinguished from O. alatiflora by its erect inflorescence, its smaller and equal-sized calyx lobes 0.5–0.7 mm long, its corolla tubes winged to the middle and the wings straight and its strongly reflexed corolla lobes at anthesis. Ophiorrhiza reflexa is assessed as least concern (LC) according to IUCN Categories and Criteria

Effects of Different Nitrogen Allocation Ratios and Period on Cotton Yield and Nitrogen Utilization

Choosing the proper fertilizer regime for a crop in a given location remains challenging to increase yield, profitability, environmental growth protection, and sustainability. However, the nutrient demand characteristics of cotton in the North China Plain are different at various growth stages. Therefore, we choose the local superior cotton variety (Lumian 532) with high yield as the material, in the present study, we assessed the cotton yield, biomass accumulation and distribution, nitrogen absorption and utilization efficiency, and other parameters by setting four nitrogen allocation ratios (3:5:2, 0:10:0, 3:7:0, and 0:7:3) when the nitrogen application rates were 0, 150, 220, and 300 kg hm−2. The results showed that when the nitrogen application rate was 300 kg hm−2, the growth index, biomass, nitrogen content, and yield of Lumian 532 were the highest, while the nitrogen partial productivity (12.2 and 12.8) was the lowest. When the nitrogen application rate was 220 kg hm−2 and the nitrogen allocation ratio was 3:5:2, the agronomic nitrogen use efficiency (3.2 and 3.5) and nitrogen physiological (24.8 and 25.0) was achieved. When the nitrogen application rate was 150 kg hm−2, the nitrogen partial productivity (20.6 and 20.9) was the highest. In conclusion, the biomass accumulation and distribution, nitrogen use efficiency, yield, and yield composition of Lumian 532 could be effectively regulated by appropriate nitrogen application rate and nitrogen allocation ratio. Therefore, to optimize the yield and improve the nitrogen use efficiency, the optimal nitrogen application rate of Lumian 532 was 220 kg hm−2, and the optimal nitrogen allocation ratio was 3:5:2 in the North China Plain. The results provided practical basis for nutrient demand, cotton yield and ecological protection in different growth stages of cotton in North China Plain