The role of root size and root efficiency in grain production, and water-and nitrogen-use efficiency in wheat

BACKGROUND

The root system is the major plant organ involved in water and nutrient acquisition, influencing plant growth and productivity. However, the relative importance of root size and uptake efficiency remains undetermined. A pot experiment was conducted using two wheat varieties with different root sizes to evaluate their capacity for water and nitrogen (N) uptake and their effects on grain production, water-use efficiency (WUE), and N-use efficiency (NUE) under two water treatments combined with three N levels.

RESULTS

The leaf water potential and root exudates of changhan58 (CH, small root variety) were higher or similar to those of changwu134 (CW, large root variety) under water/N treatment combinations, indicating that small roots can transport enough water to above the ground. The addition of N improved plant growth, photosynthetic traits, and WUE significantly. There were no significant differences in WUE or grain production between the two cultivars under well-watered conditions. However, they were significantly higher in CH than in CW under water deficit stress. Nitrogen uptake per unit root dry weight, glutaminase, and nitrate reductase activities were significantly higher in CH than in CW, regardless of moisture conditions. Root biomass was positively correlated with evapotranspiration, while the root/shoot ratio was negatively correlated with WUE (P < 0.05) but not with NUE.

CONCLUSION

In a pot experiment, water and N uptake were more strongly associated with resource uptake availability than root size. This may provide guidance in wheat breeding programs for drought-prone regions. © 2023 Society of Chemical Industry.

Threshold effects of green technology application on sustainable grain production: Evidence from China

Sustainable production is considered as an important approach to solve the dilemma of food insecurity. Green technologies have made contributions to improving food production and reducing environmental pollution. Studying the effects of green technologies on sustainable food production has great significance. The paper started with the influence mechanism of green technology application on the green total factor productivity of grain (GTFPG). With the GTFPG, green technology efficiency change of grain (GECG) and green technical progress change of grain (GTCG) measured, threshold models were constructed to explore the nonlinear impacts of various green technologies on GTFPG and the influence paths. Results indicated that the differences of GTFPG among provinces in China were decreased mainly due to the changes of GTCG, while the regional differences of GECG remained small. The impacts of green technologies had threshold effects that depended on the ecological effects of green technologies in different application stages, and were significantly different in the major and non-major grain producing areas. Meanwhile, significant differences existed in the influence paths of green technologies. In the major grain producing areas, green technologies were more likely to improve GTFPG through the GTCG path; while in the non-major grain producing areas, the GECG path and the GTCG path were both important to improve GTFPG. The differences of green technologies' threshold effects and influence paths in the major and non-major grain producing areas were caused by regional technology preference, resource endowment and technology compatibility. This study emphasizes that the development of green technologies should fully consider the resource endowment and economic development of different regions, as well as the applicability and adoption rate of green technologies.

Decoupling and Decomposition Analysis of Agricultural Carbon Emissions: Evidence from Heilongjiang Province, China

Ensuring food security and curbing agricultural carbon emissions are both global policy goals. The evaluation of the relationship between grain production and agricultural carbon emissions is important for carbon emission reduction policymaking. This paper took Heilongjiang province, the largest grain-producing province in China, as a case study, estimated its grain production-induced carbon emissions, and examined the nexus between grain production and agricultural carbon emissions from 2000 to 2018, using decoupling and decomposition analyses. The results of decoupling analysis showed that weak decoupling occurred for half of the study period; however, the decoupling state and coupling state occurred alternately, and there was no definite evolving path from coupling to decoupling. Using the log mean Divisia index (LMDI) method, we decomposed the changes in agricultural carbon emissions into four factors: agricultural economy, agricultural carbon emission intensity, agricultural structure, and agricultural labor force effects. The results showed that the agricultural economic effect was the most significant driving factor for increasing agricultural carbon emissions, while the agricultural carbon emission intensity effect played a key inhibiting role. Further integrating decoupling analysis with decomposition analysis, we found that a low-carbon grain production mode began to take shape in Heilongjiang province after 2008, and the existing environmental policies had strong timeliness and weak persistence, probably due to the lack of long-term incentives for farmers. Finally, we suggested that formulating environmental policy should encourage farmers to adopt environmentally friendly production modes and technologies through taxation, subsidies, and other economic means to achieve low-carbon agricultural goals in China.

The Remarkable Journey of a Weed: Biology and Management of Annual Ryegrass (Lolium rigidum) in Conservation Cropping Systems of Australia

Annual ryegrass (Lolium rigidum Gaud.), traditionally utilised as a pasture species, has become the most problematic and difficult-to-control weed across grain production regions in Australia. Annual ryegrass has been favoured by the adoption of conservation tillage systems due to its genetic diversity, prolific seed production, widespread dispersal, flexible germination requirements and competitive growth habit. The widespread evolution of herbicide resistance in annual ryegrass has made its management within these systems extremely difficult. The negative impacts of this weed on grain production systems result in annual revenue losses exceeding $93 million (AUD) for Australian grain growers. No single method of management provides effective and enduring control hence the need of integrated weed management programs is widely accepted and practiced in Australian cropping. Although annual ryegrass is an extensively researched weed, a comprehensive review of the biology and management of this weed in conservation cropping systems has not been conducted. This review presents an up-to-date account of knowledge on the biology, ecology and management of annual ryegrass in an Australian context. This comprehensive account provides pragmatic information for further research and suitable management of annual ryegrass.

The Adjustment of China's Grain Planting Structure Reduced the Consumption of Cropland and Water Resources

Driven by technological progress and market demand, the optimization and adjustment of grain planting structure played an important role in increasing grain output. Due to the great difference between the yield per unit area of different types of food crops, the consumption of cropland and water resources has a significant change during the grain growth. From the perspective of structural adjustment, rather than the usual productive factor input, we analyze the process of adjustment for grain planting structure in China and its effect on the consumption of cropland and water resources by using the scenario comparative analysis method. The results show that: (1) From 2003 to 2019, China’s grain output has increased steadily and the planting structure has changed greatly. Rice was replaced by corn to become the grain crop with the maximum proportion of planting area since 2007. The increase of corn planting structure proportion is concentrated in the northern regions. (2) At the national level, according to the adjustment of grain planting structure, the saving of cropland and water resources consumption showed a “cumulative effect” as time went on. (3) The saving effects of structural adjustment in the northern regions on cropland and water resources consumption are better than that in the southern regions, such as Northeast China Plain, Northern arid and semiarid region and Loess Plateau. (4) In reality, although the adjustment of grain planting structure saved lots of cropland and water resources, the continuous growth of grain output has increased the pressure on the ecological environment in the northern regions according to theirs water limits. Therefore, it is necessary to continuously optimize the grain planting structure and restrict land reclamation in northern China. In addition, to ensure food security, it is feasible to encourage the southern regions with abundant water and heat resources to increase the grain planting area and meet its self-sufficiency in grain demand.

Spatial-Temporal Characteristics in Grain Production and Its Influencing Factors in the Huang-Huai-Hai Plain from 1995 to 2018

The Huang-Huai-Hai Plain is the major crop-producing region in China. Based on the climate and socio-economic data from 1995 to 2018, we analyzed the spatial-temporal characteristics in grain production and its influencing factors by using exploratory spatial data analysis, a gravity center model, a spatial panel data model, and a geographically weighted regression model. The results indicated the following: (1) The grain production of eastern and southern areas was higher, while that of western and northern areas was lower; (2) The grain production center in the Huang-Huai-Hai Plain shifted from the southeast to northwest in Tai'an, and was distributed stably at the border between Jining and Tai'an; (3) The global spatial autocorrelation experienced a changing process of "decline-growth-decline", and the area of hot and cold spots was gradually reduced and stabilized, which indicated that the polarization of grain production in local areas gradually weakened and the spatial difference gradually decreased in the Huang-Huai-Hai Plain; (4) The impact of socio-economic factors has been continuously enhanced while the role of climate factors in grain production has been gradually weakened. The ratio of the effective irrigated area, the amount of fertilizer applied per unit sown area, and the average per capita annual income of rural residents were conducive to the increase in grain production in the Huang-Huai-Hai Plain; however, the effect of the annual precipitation on grain production has become weaker. More importantly, the association between the three factors and grain production was found to be spatially heterogeneous at the local geographic level.

Climate, human influence and the distribution limits of the invasive European earwig, Forficula auricularia, in Australia

BACKGROUND

By modelling species-environment relationships of pest species, it is possible to understand potential limits to their distributions when they invade new regions, and their likely continued spread. The European earwig, Forficula auricularia, is a non-native invasive species in Australia that has been in the country for over 170 years. However, in the last few decades it has invaded new areas. Unlike in other countries, F. auricularia is a pest species of grain production in Australia. In this study we detail the Australian distribution of this species, adding new samples focused around grain-growing regions. Using this information, we build global species distribution models for F. auricularia to better understand species-environment relationships.

RESULTS

Our models indicate that the distribution of F. auricularia is strongly associated with temperate through to semi-arid environments, a high winter rainfall and pronounced temperature seasonality. We identified regions that hold suitable, but as yet vacant, niche space for Australian populations, suggesting further potential for range expansion. Beyond climate, an index describing human influence on the landscape was important to understand the distribution limits of this pest. We identified regions where there was suitable climate space, but which F. auricularia has not occupied, probably due to low levels of human impact.

CONCLUSION

Modelling the global distribution of a non-native pest species aided understanding of the regional distribution limits within Australia and highlighted the usefulness of human impact measures for modelling globally invasive insect species. © 2018 Society of Chemical Industry.

Mitigating Groundwater Depletion in North China Plain with Cropping System that Alternate Deep and Shallow Rooted Crops

In the North China Plain, groundwater tables have been dropping at unsustainable rates of 1 m per year due to irrigation of a double cropping system of winter wheat and summer maize. To reverse the trend, we examined whether alternative crop rotations could save water. Moisture contents were measured weekly at 20 cm intervals in the top 180 cm of soil as part of a 12-year field experiment with four crop rotations: sweet potato→ cotton→ sweet potato→ winter wheat-summer maize (SpCSpWS, 4-year cycle); peanuts → winter wheat-summer maize (PWS, 2-year cycle); ryegrass-cotton→ peanuts→ winter wheat-summer maize (RCPWS, 3-year cycle); and winter wheat-summer maize (WS, each year). We found that, compared to WS, the SpCSpWS annual evapotranspiration was 28% lower, PWS was 19% lower and RCPWS was 14% lower. The yield per unit of water evaporated improved for wheat within any alternative rotation compared to WS, increasing up to 19%. Average soil moisture contents at the sowing date of wheat in the SpCSpWS, PWS, and RCPWS rotations were 7, 4, and 10% higher than WS, respectively. The advantage of alternative rotations was that a deep rooted crop of winter wheat reaching down to 180 cm followed shallow rooted crops (sweet potato and peanut drawing soil moisture from 0 to 120 cm). They benefited from the sequencing and vertical complementarity of soil moisture extraction. Thus, replacing the traditional crop rotation with cropping system that involves rotating with annual shallow rooted crops is promising for reducing groundwater depletion in the North China Plain.

The response of grain production to changes in quantity and quality of cropland in Yangtze River Delta, China

BACKGROUND

Cropland in Yangtze River Delta has declined drastically since economic reforms in 1978 that led to rapid economic development. Such cropland loss due to population growth has led to a decline in grain production. This study aimed at analyzing the impact of land use changes on grain production. To achieve this, the spatiotemporal dynamics of cropland during 1980-2010 were analyzed. Irrigation and soil fertility data were used as additional lines of evidence.

RESULTS

Cropland loss had negative impacts on grain production. About 80 and 66% of grain production decreased during 1980-2005 and 2005-2010 respectively. This decline was attributed to the conversion of cropland to built-up areas. Abandoned cropland areas were mainly concentrated in regions with high irrigation capability and high soil fertility, while cropland reclamation was mainly in areas with low irrigation and soil fertility, implying that, although cropland was reclaimed, production remained low. The decline in cropland area has reinforced the chronic food insecurity in Yangtze River Delta.

CONCLUSION

This study demonstrated the response of grain production to the changes in cropland quantity and quality. It also provides scientific evidence for decision makers to protect cropland and enhance grain production.