Wheat-Maize Intercropping With Reduced Tillage and Straw Retention: A Step Towards Enhancing Economic and Environmental Benefits in Arid Areas

Intercropping is considered a promising system for boosting crop productivity. However, intercropping usually requires higher inputs of resources that emit more CO2. It is unclear whether an improved agricultural pattern could relieve this issue and enhance agricultural sustainability in an arid irrigation area. A field experiment using a well-designed agricultural practice was carried out in northwest China; reduced tillage, coupled with wheat straw residue retention measures, was integrated with a strip intercropping pattern. We determined the crop productivity, water use, economic benefits, and carbon emissions (CEs). The wheat-maize intercropping coupled with straw covering (i.e., NTSI treatment), boosted grain yield by 27–38% and 153–160% more than the conventional monoculture of maize and wheat, respectively, and it also increased by 9.9–11.9% over the conventional intercropping treatment. Similarly, this pattern also improved the water use efficiency by 15.4–22.4% in comparison with the conventional monoculture of maize by 45.7–48.3% in comparison with the conventional monoculture of wheat and by 14.7–15.9% in comparison with the conventional intercropping treatment. Meanwhile, NTSI treatment caused 7.4–13.7% and 37.0–47.7% greater solar energy use efficiency than the conventional monoculture of maize and wheat, respectively. Furthermore, the NTSI treatment had a higher net return (NR) by 54–71% and 281–338% and a higher benefit per cubic meter of water (BPW) by 35–51% and 119–147% more than the conventional monoculture of maize and wheat, respectively. Similarly, it increased the NR and BPW by 8–14% and 14–16% in comparison with the conventional intercropping treatment, respectively. An additional feature of the NTSI treatment is that it reduced CEs by 13.4–23.8% and 7.3–17.5% while improving CE efficiency by 62.6–66.9% and 23.2–33.2% more than the conventional monoculture maize and intercropping treatments, respectively. We can draw a conclusion that intercropping maize and wheat, with a straw covering soil surface, can be used to enhance crop production and NRs while effectively lowering CO2 emissions in arid oasis irrigation region

Low N Fertilizer Application and Intercropping Increases N Concentration in Pea (Pisum sativum L.) Grains

Sustainable intensification of pulses needs reduced input of nitrogen (N) fertilizer with enhanced crop nutritional quality and yield. Therefore, increasing N harvest in grains (sink organs) by improving N remobilization is of key importance. Previous research has shown that a lower dose of N fertilizer effectively increases the rate of N remobilization, while intercropping improves the grain N concentration in pea (Pisum sativum L.). However, it is unknown whether intercropping can facilitate this N fertilizer effect to increase N remobilization, and thereby enhance the N harvest index (NHI). In this study, we determined N allocation among different organs of pea plants, N translocation from leaf and stem tissues to pods, N2 fixation, N utilization efficiency, and NHI of pea plants grown alone or intercropped with maize (Zea mays L.) with different N fertilization treatments in a field experiment in northwestern China from 2012 to 2014. A base application of 90 kg N ha−1 at sowing and top-dress application of 45 kg N ha−1 at flowering integrated with maize–pea intercropping increased N allocation to pod tissues, N translocation to grains, and NHI of pea plants. Compared with the application of 90 kg N ha−1 at sowing and 135 kg N ha−1 top-dressed at flowering, reducing the top-dress application of N fertilizer to 45 kg N ha−1 increased N allocation to intercropped pea plants by 8%. Similarly, N translocation to grains from leaf and stem tissues was increased by 37.9 and 43.2%, respectively, enhancing the NHI by 40.1%. A positive correlation between N2 fixation and NHI was observed, implying that N2 fixation improves N concentration in grain sinks. Thus, our data show that growing pulses in an intercropping system with reduced N fertilization are essential for maximizing N translocation, improving nutritional quality, and preventing the loss of N through leaching, thereby avoiding potential groundwater contamination

Optimized Nitrogen Rate, Plant Density, and Regulated Irrigation Improved Grain, Biomass Yields, and Water Use Efficiency of Maize at the Oasis Irrigation Region of China

Nitrogen is a key factor in maize (Zea mays L.) grain and biomass production. Inappropriate application with sub-optimum plant density and irrigation can lead to low productivity and inefficient use. A two-year field experiment was conducted to determine which nitrogen rate, plant density, and irrigation level optimize grain, biomass yield, and water use efficiency. Three nitrogen rates of urea (46–0–0 of N–P2O5–K2O) (N0 = 0 kg N ha−1, N1 = 270 kg N ha−1, and N2 = 360 kg N ha−1), with three maize densities (D1 = 75,000 plants ha−1, D2 = 97,500 plants ha−1, and D3 = 120,000 plants ha−1), and two irrigation levels (W1 = 5250 m3/hm2 and W2 = 4740 m3/hm2) were investigated. The results show that both grain and biomass yields were affected by the main factors. The interaction between nitrogen rate and irrigation level significantly (p < 0.001) affected grain yield but not biomass. It was observed that the grain yield increased correspondingly with nitrogen rate and plant density, while it decreased as the irrigation level increased. Water use efficiency was significantly (p < 0.001) affected by the main factors and their interactions. Nevertheless, water use efficiency was highest at (5250 m3/hm2) × 270 kg N ha−1; × 360 kg N ha−1 × 120,000 plants ha−1 and increased from 62% to 68%. In addition, the highest biomass yield was recorded at 5250 m3/hm2 × 270 kg N ha−1; × 360 kg N ha−1 × 120,000 plants ha−1 while the interaction of either irrigation level with 0 and 270 kg ha−1 or 97,500 and 120,000 plants ha−1 yielded the lowest water use efficiency. Thus, optimized nitrogen rates, plant density, and alternate irrigation levels can support optimum grain and biomass yields. It can also improve nitrogen and water use efficiency in maize production

Optimized Nitrogen Rate, Plant Density, and Regulated Irrigation Improved Grain, Biomass Yields, and Water Use Efficiency of Maize at the Oasis Irrigation Region of China

Nitrogen is a key factor in maize (Zea mays L.) grain and biomass production. Inappropriate application with sub-optimum plant density and irrigation can lead to low productivity and inefficient use. A two-year field experiment was conducted to determine which nitrogen rate, plant density, and irrigation level optimize grain, biomass yield, and water use efficiency. Three nitrogen rates of urea (46–0–0 of N–P2O5–K2O) (N0 = 0 kg N ha−1, N1 = 270 kg N ha−1, and N2 = 360 kg N ha−1), with three maize densities (D1 = 75,000 plants ha−1, D2 = 97,500 plants ha−1, and D3 = 120,000 plants ha−1), and two irrigation levels (W1 = 5250 m3/hm2 and W2 = 4740 m3/hm2) were investigated. The results show that both grain and biomass yields were affected by the main factors. The interaction between nitrogen rate and irrigation level significantly (p p 3/hm2) × 270 kg N ha−1; × 360 kg N ha−1 × 120,000 plants ha−1 and increased from 62% to 68%. In addition, the highest biomass yield was recorded at 5250 m3/hm2 × 270 kg N ha−1; × 360 kg N ha−1 × 120,000 plants ha−1 while the interaction of either irrigation level with 0 and 270 kg ha−1 or 97,500 and 120,000 plants ha−1 yielded the lowest water use efficiency. Thus, optimized nitrogen rates, plant density, and alternate irrigation levels can support optimum grain and biomass yields. It can also improve nitrogen and water use efficiency in maize production

Wheat and maize relay-planting with straw covering increases water use efficiency up to 46 %

International audienceFamily farms in populated countries must produce sufficient quantities of food to meet the ever-growing population needs. It is unknown whether innovated farming systems can alleviate this issue. Here, we carried out field experiments in arid northwest China from 2009 to 2012 to determine the response of water use, grain yield, and water use efficiency. We integrated crop intensification via relay-planting and straw mulching in the same system. Straw mulching included stubble standing, straw covering, or straw incorporation to the soil. Results show that wheat and maize relay-planting with straw mulching increased yields by up to 153 % versus mono-planting of maize and wheat. Straw covering approached the highest yield. Relay-planting with stubble standing or straw covering decreased water consumption by 4.6 %. The integrated systems increased water use efficiency by up to 46 % compared to conventional mono-planting maize and wheat

Water spectrum method of NMR logging for identifying fluids

A new fluid identification method by constructing water spectrum based on NMR logging was put forward after the limitations of existing nuclear magnetic resonance (NMR) fluid identification methods were analyzed. At present, differential spectrum method (DSM) and shifted spectrum method (SSM) of NMR logging are commonly used fluid identification methods. Due to the effects of fluid properties and pore structures, however, their coincidence rates of fluid identification are lower. A new fluid identification method named water spectrum construction method was developed in this study. Based on the existing acquisition mode of NMR logging, T2 (transverse relaxation time) spectrum of long waiting time and long echo spacing in completely watered conditions was constructed from the T2 spectrum which was measured in the mode of long waiting time and short echo spacing. And then, the types of fluids in reservoirs were identified by comparing the measured T2 spectrum with the constructed water spectrum. This new method was applied in Nanpu sag, Bohai Bay Basin for identifying oil layers, oil-water layers, water layers, gas layers and low-resistivity oil layers. It is demonstrated that based on the water spectrum construction method, the coincidence rate of fluid identification caused by pore structures is increased and fluid identification capacity of NMR logging is improved. Water spectrum construction method is prospective for fluid identification and evaluation of complex reservoirs. Key words: NMR logging, water spectrum method, fluid identification technique, complex reservoirs, fluid identification coincidence rat

Fluid identification method based on 2D diffusion-relaxation nuclear magnetic resonance (NMR)

Based on current acquisition modes of MRIL-Prime NMR logging tool, 2D NMR signals could be obtained by the combination of logging data from different modes, then the fluid properties in complicated reservoirs could be distinguished by 2D diffusion-relaxation NMR logging data distribution of pore fluids, generated by multi-echotrain joint inversion. In comparison with 1D NMR logging, this method could increase fluid information in diffusion regime, separate oil, gas and water signals in 2D space and enhance the identification capacity of fluid properties from NMR logging. The 2D NMR logging in the multi-echowave interval was applied in the oil pays in Well A and the water layers in Well B in the Nanpu Sag by MRIL-Prime tool, and the interpretation matches the well testing result. It indicates that 2D NMR logging has advantages on the identification of light oil, and fluids in macropore reservoirs than 1D NMR logging. Key words: 2D NMR logging, acquisition mode, joint multi-echotrain inversion, diffusion coefficien

Less carbon emissions of wheat–maize intercropping under reduced tillage in arid areas

International audienceIntercropping is used to increase grain production in many areas of the world. However, this increasing crop yield costs large amounts of water used by intercropped plants. In addition, intercropping usually requires higher inputs that induce greenhouse gas emissions. Actually, it is unknown whether intercropping can be effective in water-limited arid areas. Here, we measured crop yield, water consumption, soil respiration, and carbon emissions of wheat–maize intercropping under different tillage and crop residue management options. A field experiment was conducted at Wuwei in northwest China in 2011 and 2012. Our results show that wheat–maize intercropping increased grain yield by 61 % in 2011 and 63 % in 2012 compared with the average yield of monoculture crops. The intercropping under reduced tillage with stubble mulching yielded 15.9 t ha−1 in 2011 and 15.5 t ha−1 in 2012, an increase of 7.8 % in 2011 and 8.1 % in 2012, compared to conventional tillage. Wheat–maize intercropping had carbon emission of 2,400 kg C ha−1 during the growing season, about 7 % less than monoculture maize, of 2,580 kg C ha−1. Reduced tillage decreased C emission over conventional tillage by 6.7 % for the intercropping, 5.9 % for monoculture maize, and 7.1 % for monoculture wheat. Compared to monoculture maize, wheat–maize intercropping used more water but emitted 3.4 kg C per hectare per millimeter of water used, which was 23 % lower than monoculture maize. Overall, our findings show that maize–wheat intercropping with reduced tillage coupled with stubble mulching can be used to increase grain production while effectively lower carbon emissions in arid areas

Well logging evaluation of Triassic Chang 7 Member tight reservoirs, Yanchang Formation, Ordos Basin, NW China

Taking the Triassic Chang 7 Member tight reservoirs of the Yanchang Formation in the Ordos Basin as study object, transverse relaxation simulation was made using nuclear magnetic resonance (NMR) experimental data, CT images and random-walker algorithm to evaluate microscopic pore-throats of the tight reservoirs. The smoothing degree of well logging curves was utilized to evaluate sand structure of the tight reservoirs; and through multi-well analysis and the calibration of well testing data, a grading chart of tight reservoir productivity was established based on sand structure. Reservoir quality was judged and analyzed by pore level: Transverse surface relaxivity ρ2 was obtained by comparing transverse relaxation time T2 of numerical simulation and that of NMR experiment, and the distribution of pore-throat radius was obtained according to the corrected NMR logging curves. The study shows there is an obvious correlation between productivity and sand structure of Chang 7 tight reservoirs. The more homogeneous the distribution of lithology, physical property and oiliness of the massive sand, and the smoother the well logging curves, the more likely the high oil yield will occur. Based on well logging evaluation and grading chart of productivity of tight reservoirs, sweet spots in well area W of Jiyuan Oilfield in Ordos Basin were identified, the comparison of the evaluation results and well testing data shows the accuracy rate is as high as 94.7%. Key words: tight oil, well logging evaluation, microscopic pore-throat distribution, sand structure, sweet spot distribution, Ordos Basi