Silicon alleviates salinity stress in licorice (Glycyrrhiza uralensis) by regulating carbon and nitrogen metabolism.

Salt stress is one of the key factors that limits the cultivation of Glycyrrhiza uralensis Fisch. (G. uralensis) in the northern part of China. In this study, three salt treatments (including 21, 42 and 63 ds/m NaCl/kg dry soil) and four Si (silicon) concentrations (including 0, 1.4, 2.8 and 4.2 ds/m SiO2/kg K2SiO3 in dry soil) were tested using G. uralensis as the plant material in a pot experiment with three replications. The results showed that the application of various concentrations of Si increased sucrose synthetase (SS), sucrose phosphate synthetase (SPS) and glutamine synthetase (GS), as well as nitrate reductase (NR) activities, and promoted carbon and nitrogen metabolism. Si application also increased the root dry weight of G. uralensis. Multilevel comparative analysis showed that the application of 2.8 ds/m SiO2 was the optimum rate for improved growth and yield of G. uralensis under different salt levels. This study provides important information that can form the basis for the cultivation of high-yielding and high-quality G. uralensis in saline soils.

Effects of mulching on soil CO2 fluxes, hay yield and nutritional yield in a forage maize field in Northwest China.

In arid areas of China, water shortage and heavy carbon emissions have been threatening agricultural sustainability and which has become a vital issue. A field experiment was conducted to explore how different mulching affects soil moisture and temperature, CO2 fluxes, forage-maize hay yield and nutritional value during 2 consecutive years: 2014 and 2015. The field experiment showed that mulching materials had distinct effects on soil moisture and temperature and CO2 fluxes. The soil temperature and CO2 fluxes were in order of common plastic film mulching (PFM) > bio-degradable mulch mulching (BMM) > no mulching (CK) > straw mulching (SM), while the soil moisture was in order of PFM > BMM > SM > CK over these two years. Compared with CK, hay yield respectively increased by 23.25%, 22.51% and 5.27% for PFM, BMM and SM, WUE increased by 35.60%, 32.34% and 10.88%, and the total nutrient yields increased by 17.75%, 21.35% and 6.95%, respectively. To sum up, in combination with ecology and environmental protection, bio-degradable mulch could replace common plastic film and bio-degradable mulch should be popular in future. As bio-degradable mulch is green non-pollution, it is conducive to the sustainable development of agricultural ecosystem.

[Effects of stubble-standing mode on the grain yield and water use efficiency of wheat and maize in wheat/maize intercropping system].

Wheat/maize intercropping is the main intercropping pattern in the irrigation region of Hexi Oasis, Northwest China, but the traditional intercropping needs much water, making the regional water resource lacked increasingly. In 2010, a field experiment was conducted in the irrigation region of Shiyang River basin oasis, Gansu Province of Northwest China, aimed to study the effects of traditional stubble-burning, stubble-returning, and stubble-standing on the grain yield, water use efficiency (WUE), and economical benefits of wheat and maize in wheat/maize inter-cropping system. Compared with stubble-burning and stubble-returning, stubble-standing increased the grain yield of mono- and intercropped wheat by 7.2% and 5.1% , and 6.2%, 5.1%, and that of mono- and intercropped maize by 4.7% and 2.5%, and 7.2% and 3.3%, and increased the WUE of mono- and intercropped wheat by 20.4% and 16.2%, and 17.9% and 14.6%, and that of mono- and intercropping maize by 16.7% and 10.9%, and 11. 8% and 17.0%, respectively. As for the mono- and intercropped wheat and maize, their average net economical benefits under stubble-burning, stubble- returning, and stubble-standing were 10946, 11471, and 13454 RMB.hm-2, respectively. In considering the grain yield, WUE, and economic benefits, stubble- standing would be the optimal mode of wheat/maize intercropping in the oasis of Hexi irrigation region, Northwest China.

[Effects of different water harvesting modes on alfalfa planting in semi-arid areas of Northwest China].

A field experiment with complete random design was conducted to investigate the effects of different mulching materials [common plastic film (CMR), biodegradable mulch film (BMR), and soil crust (SR)] and different ratios of furrow to ridge (60 cm:30 cm, 60 cm:45 cm, and 60 cm:60 cm) on the runoff efficiency, soil water storage, soil water content, and hay yield and water use efficiency of alfalfa in semiarid areas of the Loess Plateau. The runoff efficiency in treatments SR, BMR, and CMR was 32.0%, 90.7%, and 96.4%, respectively. In the early growth period of alfalfa (from April to June) , the soil water storage between the treatments had no significant difference, but in the late growth period (from July to September), the soil water storage in CMR and BMR was significantly higher than that in SR. The soil water storage in SR was significantly higher than that in traditional planting (TP). At budding stage, the soil water storage in TP, SR, BMR, and CMR was 223.27, 248.56, and 277. 81, and 284.16 mm, respectively. In the whole growth period, the hay yield of alfalfa in TP, SR, BMR, and CMR was 4112.1, 3397.5, 4317.8, and 4523.8 kg x hm(-2), and the water use efficiency was 11.08, 10.48, 14.56, and 14.95 kg x mm(-1) x hm(-2), respectively. The ratio of furrow to ridge had no significant effects on the water use efficiency in the same treatments. When the ratio of furrow to ridge was 60 cm:44 cm, the hay yield in CMR and BMR reached the maximum.

[Effect of altitudes on the photosynthate accumulation and distribution pattern of Angelic sinensis].

OBJECTIVE: To study the effect of altitudes on the photosynthate accumulation and distribution pattern of Angelic sinensis in Gansu province and provide theontical for its expanding ecological planting region. METHODS: Used field test to study the photosynthate accumulation and distribution pattern of Angelic sinensis on three different altitudinal gradients from 2 300 m to 2 800 m. RESULTS: Before September 25, total photosynthate accumulation were decreased with the increasing of elevation, which amaunt was 176 g/plant, 166 g/plant and 128 g/plant, respectively. The total photosynthate of low-altitude and middle-altitude were significantly higher than that of high-altitude (P < 0.05). After September 25, middle-altitude was significantly higher than the other two altitudes (P < 0.05), respectively, by 13.9% and 11.1%. The photosynthate accumulation rate existed the altitude effects, there was no significant difference between high-altitude (46.7%) and middle-altitude (43.7%), but they were even significantly higher than that of low-altitude (33.1%). The root distribution proportion (> 30%) existed the difference, that of high-altitude was 10 days earlier than the other two altitudes, and later that of high-altitude (about 54%) was higher than the other two altitudes (49.8% - 50.9%), it laid the foundation for yield formation. Yield of Angelic sinensis was as follows: middle-altitude (28.4 g/ plant), high-altitude (26.6 g/plant) and low-altitude (21.8 g/plant). Yield of Angelic sinensis middle-altitude and high-altitude were higher than that of low-altitude, respectively, by 30.2% and 22.2%, and it had a significant difference (P < 0.05), this result was consistent with the photosynthate accumulation rate. CONCLUSION: Altitudinal gradients affect yield formation of Angelic sinensis by changing the photosynthate distribution pattern and dry matter accumulation rate. So by appropriately increasing altitude, the root distribution proportion and yield are improved, this provides theoretical reference for expanding Angelic sinensis planting ecological region.

[Effects of continuous cropping obstacle on growth of Angelica sinensis and its mechanism].

OBJECTIVE: To study the effects of continuous cropping obstacles on growth of Angelica sinensis. METHOD: The growth indexes, photosynthetic characteristic, activity of leaf protective enzymes, and the yield, essential oil content and extract content were determined. RESULT: Continuous cropping decreased the growth and the yield, essential oil content, extract content of A. sinensis. Photosynthetic pigment, which include Chla and Chlb, and photosynthetic rate of A. sinensis leaves decreased. Activity of leaf SOD, POD and CAT were also inhibited. The content of proline, soluble sugar and MDA increased. CONCLUSION: Through decreasing the activity of protective enzymes and their ability of cleaning free radical, continuous cropping made free radical remain in plant so that induced membrane lipid peroxidization, electrolytic leakage became heavier, content of proline and soluble sugar increased. The external manifestation of this influences were that plant growth was inhibited, content of photosynthetic pigments decreased, so did the intensity of photosynthesis and respiration, content of dry mass.

[Temporal and spatial distribution characteristics of the crop root in intercropping system].

The ecological mechanism of competition and compensation between the crop root systems of two different intercropping patterns, wheat-soybean and corn-cabbage, was studied by field experiment. The results showed that the annual growth peak of wheat-soybean roots in intercropping was interlacing, the growth of root weight and length expressed synchronism, and the peak of root weight was appeared earlier than that of root length. The vertical distribution of the two crops' root system in two intercroppings was reduced gradually along with soil depths, which also showed that the multiple growth waves moved progressively. The root system distributed horizontally in intercropping system also showed a clearly unbalanced distribution. The root system distribution of out-row for corn elongated 20.4-40.8 cm to cabbage rows, but that of cabbage elongated only 8.5-12.6 cm to corn. The cross extent of root systems in corn-cabbage intercropping was decreased from 40.2 cm to 20.1 cm by fertilization, and the place of cross point for root concentrated region was changed from 20.5 cm to 12.4 cm below soil surface by fertilizer supply. The place of cross point for root concentrated region was an important index to decide the degrees of competition.

[Regulation of fertilizer application on yield and root growth of spring wheat-faba bean intercropping system].

The effects of N and P fertilizer application on the multiple population yield and root growth of spring wheat (Triticum aestivum)--spring faba bean(Vicia sativa)intercropping system were studied by two field experiments with 0, 150 and 225 kgN.hm-2, three pot and pool experiments with 2 N applications (0, 100 mg N.kg-1 soil) and 3 P applications (0, 100 and 200 mg P.kg-1 soil). The results showed that this intercropping system had a significant advantage of yield and beneficial effects. Compared to Po supply, P fertilization increased the seed yield by 48.39% for intercropped spring wheat and 16.69% for intercropped faba bean in field experiment. Furthermore, the total seed yield of both crops was increased by 20.07% to 43.14% in pool culture, and the grain yield of intercropped faba bean was increased by 58.46% to 78.78%. In the intercropping system, the growth peak of root density of both crops was appeared alternately, the peak of wheat root growth being earlier than that of faba bean. The maximum root weight of intercropped wheat was in its early heading periods, whereas that of faba bean appeared at its maturity periods, which reduced the competition for water and nutrients between the crops, and resulted in yield increase. The weight, length and surface area of wheat roots in P supply were increased by 54.33%, 48.88% and 47.00%, and in N supply, they were increased by 15.25%, 11.61% and 11.46%, respectively. About 57.61% of wheat root weight and 69.20% of faba bean root weight were distributed at 0-30 cm soil depths in the treatments of receiving P fertilizer at various rates, which indicated that P supply increased root weight and length of both crops in the intercropping system.