Qiang Chai

Higher yield and lower carbon emission by intercropping maize with rape, pea, and wheat in arid irrigation areas

Food security has become a global issue, seriously threatening developing countries owing to fast-growing human populations and declining availability of land for agriculture. Increasing crop yields could be achieved by intensive systems, but these usually need higher energy and emit more carbon (C). Here, we studied crop productivity, energy yields, and C emissions of intercropping versus sole cropping. We tested maize–wheat, maize–rape, maize–pea, and soybean–wheat intercropping, and sole crops as controls in field experiments at Wuwei experimental station in from 2009 to 2011 in a randomized block design with three replicates. We used an evaluation index integrating yield and environmental factors. Results showed a yield increase of 27xa0% for maize–wheat, 41xa0% for maize–rape, and 42xa0% for maize–pea versus sole crops. Water use efficiency increased by 25xa0% for maize–wheat intercropping over sole wheat, 152xa0% for maize–rape over sole rape, and 95xa0% for maize–pea over sole pea. The three maize–crop intercrops produced 68, 308, and 256xa0% more energy yield than did the sole wheat, sole rape, and sole pea crops, respectively. They emitted 42, 52, and 45xa0% less C per unit of water in 2009, 2010, and 2011, respectively, compared with the sole maize crop. The maize-based intercropping received a the highest evaluation index (0.82 out of 1.0) among the systems evaluated, clearly showing that the maize-based intercropping is the most effective and sustainable cropping system for arid irrigation areas.

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

Intercropping 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 61xa0% in 2011 and 63xa0% in 2012 compared with the average yield of monoculture crops. The intercropping under reduced tillage with stubble mulching yielded 15.9xa0txa0ha−1 in 2011 and 15.5xa0txa0ha−1 in 2012, an increase of 7.8xa0% in 2011 and 8.1xa0% in 2012, compared to conventional tillage. Wheat–maize intercropping had carbon emission of 2,400xa0kgxa0Cxa0ha−1 during the growing season, about 7xa0% less than monoculture maize, of 2,580xa0kgxa0Cxa0ha−1. Reduced tillage decreased C emission over conventional tillage by 6.7xa0% for the intercropping, 5.9xa0% for monoculture maize, and 7.1xa0% for monoculture wheat. Compared to monoculture maize, wheat–maize intercropping used more water but emitted 3.4xa0kg C per hectare per millimeter of water used, which was 23xa0% 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.

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

Family 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 153xa0% 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 4.6xa0%. The integrated systems increased water use efficiency by up to 46xa0% compared to conventional mono-planting maize and wheat.

Farming tactics to reduce the carbon footprint of crop cultivation in semiarid areas. A review

The human population on the planet is estimated to reach 9 billion by 2050; this requires significant increase of food production to meet the demands. Intensified farming systems have been identified as a viable means to increase grain production. However, farming intensification requires more inputs such as fertilizers, pesticides, and fuels; all these emit greenhouse gases and have environmental consequences. An overwhelming question is: can farming practices be improved which enables yield increase with no cost to the environment? Here, we present seven key farming tactics that are proven to be effective in increasing grain production while lowering carbon footprint: (1) using diversified cropping systems can reduce the system’s carbon footprint by 32 to 315xa0% compared with conventional monoculture systems; (2) improving N fertilizer use efficiency can lower the carbon footprints of field crops as N fertilizer applied to these crops contributed 36 to 52xa0% of the total emissions; (3) adopting intensified rotation with reduced summerfallow can lower the carbon footprint by as much as 150xa0%, compared with a system that has high frequency of summerfallow; (4) enhancing soil carbon sequestration can reduce carbon footprint, as the emissions from crop inputs can be partly offset by carbon conversion from atmospheric CO2 into plant biomass and ultimately sequestered into the soil; (5) using reduced tillage in combination with crop residue retention can increase soil organic carbon and reduce carbon footprints; (6) integrating key cropping practices can increase crop yield by 15 to 59xa0%, reduce emissions by 25 to 50xa0%, and lower the carbon footprint of cereal crops by 25 to 34xa0%; and (7) including N2-fixing pulses in rotations can reduce the use of inorganic fertilizer, and lower carbon footprints. With the adoption of these improved farming tactics, one can optimize the system performance while reducing the carbon footprint of crop cultivation.