Yuyun Bi

Returning straw to the field is the most significant straw utilization technique for China’s green development. It can provide nutrients for crop growth and improve soil organic matter content. However, there are no standard parameters for measuring the nutrient content of straw directly returned to the field. In addition, the nutrient content of straw in the field is disregarded and the least researched. Therefore, to address these issues, the current research examines the main nutrient composition of straw returned directly to fields and the potential substitution of straw for chemical fertilizers. This study used the latest data on the crop straw-to-grain ratio and straw’s direct return to the field from the Database of Agricultural Crops Straws Resources in China (DACSRC) as the basis for a detailed estimation of the amount of crop straw nutrient resources and straw’s direct return to the field. The straw nutrient resources were measured based on straw yield and the nitrogen (N), phosphorous (P₂O₅), and potassium (K₂O) contents. The results reveal that the maximum amount of straw returned directly to the fields in China was 517 teragram (Tg), while 128 Tg (25%) of the total was not collected but left on the field. The North China region had an enormous amount of direct straw return at 176 Tg (34%), while South China had the least amount at 26 Tg (5%). The amounts of seasonally available N, P₂O₅, and K₂O from straw directly returned to fields are 2 Tg, 1 Tg, and 7 Tg, respectively. In addition, the amount of available straw nutrient resources returned to the field per hectare (ha) was 78 kg. The quantity of straw-originating seasonally available nutrients corresponds to 23% of the chemical fertilizers applied, which can substitute 10% N, 9% P₂O₅, and 58% K₂O. The study provides critical insights on effective ways to improve straw fertilization through an increased rate of straw returned directly to fields and releasing seasonal nutrients.

Agricultural sensors are essential technologies for smart agriculture, which can transform non-electrical physical quantities such as environmental factors. The ecological elements inside and outside of plants and animals are converted into electrical signals for control system recognition, providing a basis for decision-making in smart agriculture. With the rapid development of smart agriculture in China, agricultural sensors have ushered in opportunities and challenges. Based on a literature review and data statistics, this paper analyzes the market prospects and market scale of agricultural sensors in China from four perspectives: field farming, facility farming, livestock and poultry farming and aquaculture. The study further predicts the demand for agricultural sensors in 2025 and 2035. The results reveal that China’s sensor market has a good development prospect. However, the paper garnered the key challenges of China’s agricultural sensor industry, including a weak technical foundation, poor enterprise research capacity, high importation of sensors and a lack of financial support. Given this, the agricultural sensor market should be comprehensively distributed in terms of policy, funding, expertise and innovative technology. In addition, this paper highlighted integrating the future development direction of China’s agricultural sensor technology with new technologies and China’s agricultural development needs.

Enormous quantities of straw in China are burnt in open fields or discarded randomly, leading to a serious waste of biomass resources and environmental pollution. To accelerate sustainable development, straw resources must be used efficiently and reduce carbon emissions. Based on a systematic literature review, this study summarizes China’s latest development in straw utilization. It analyzes the accounting methods, carbon emission reduction effects and potential of straw utilization. The study highlights that straw utilization in China can be categorized into five-dimensional straw utilization models (FDSUM). The cost of collection, storage and transportation, and straw utilization technology are the main factors affecting straw utilization. FDSUM contributes greatly to agricultural carbon reduction. Straw-to-fertilizer has the highest contribution, and straw-to-fuel has the largest carbon emission reduction potential. The carbon emission reduction from straw–to-fuel utilization in 2020 was 63.43 × 10⁹ kg CO₂. In addition, China has not developed a standardized carbon accounting method for straw utilization. China needs to prioritize straw-to-fertilizer and straw-to-fuel conversion and develop low-carbon production technologies. This study will serve as a reference to further improve the utilization of straw in China and provide preliminary ideas for establishing a unified national carbon accounting system for straw utilization.

Renewable energy is predicted to play a crucial role in the energy sector as transitioning from fossil fuels to biofuels is key to achieving carbon neutrality. The comprehensive utilization of livestock manure and crop residues as a viable source of biofuels can play a significant role in Ghana’s future energy system. This current study aims to examine and predict the biofuel potential in Ghana from animal manure and crop residues. The biogas-biomethane potential of animal manure is determined using anaerobic digestion technology, whereas crop residues’ bioethanol potential is assessed using computational and analytical approaches. The findings demonstrate that animal manure biogas potential is 237.72 normal million cubic meters (NMm³). The highest manure-biogas potential per animal is from cattle (27.15 Nm³) and pigs (18.15 Nm³), while the least contribution is from chickens (1.80 Nm³). In addition, the annual bioethanol production is 3.74 gigaliters (GL), and residues from maize (0.88 GL), yams (0.82 GL), and plantains (0.47 GL) had the largest share per annum. By 2100, Ghana has the potential to produce 1288.56 NMm³ of manure-based biogas which can offset 13.88% of liquefied petroleum gas (LPG) consumption. The biogas potential positively correlates with the biomethane potential of 901.99 NMm³. Furthermore, 91.85% of the 14.76 GL of bioethanol will be from food crop residues. This study provides critical information to lawmakers and energy planners with strategies to achieve energy security and minimize the ecological footprint in an optimistic scenario.

Anthropogenic global warming and the depletion of nonrenewable resources necessitate a transition towards bioenergy to accelerate sustainable development and carbon neutrality. This study quantified the availability and energy potential of crop (cereals, legumes, roots and tubers) straws based on data from the Northern, North East and Savannah regions in Ghana. The annual technical straw potential was 2,967,933 tonnes, whilst the crop straws with the highest technical potential were yam (935,927 tonnes), groundnut (485,236 tonnes), maize (438,926 tonnes) and soybean (374,564 tonnes). The technical energy potential of all the crop straws was 42,256 TJ, although the energy potential of yam, groundnut, maize and soybean was 13,922 TJ, 7611 TJ, 5704 TJ and 5409 TJ, respectively. There was a linear correlation between the straw produced and the energy potential per region. The Northern region (28,153 TJ) recorded the highest energy potential followed by the Savannah (8330 TJ) and North East (5773 TJ) regions. To serve as context, the research placed an emphasis on the sustainability of crop straws for bioenergy and added a brief analysis of the life cycle assessment (LCA) of bioenergy scenarios to explore the environmental sustainability of crop straw-based power generation. This study will serve as a reference in understanding LCA inference on practicable research of crop straw-based, power plant expansion in Ghana and Sub-Saharan Africa (SSA).

Returning straw to the field has become the most important straw utilization method in China. The aim of this research was to study the appropriate amount of nitrogen fertilizer applied when returning the straw of three major crops (wheat, rice, and corn) to the field in areas under low to high yield levels based on the demand of nitrogen for microbial decomposition of straw. Under the condition of returning 100% straw to the field, we developed the formula for calculating the nitrogen application rate and estimated the urea application rate for the three major grain crops. The results showed that returning straws of wheat, early-season rice, middle-season rice and late-season rice, and corn to the field with urea application at the rate of about 150 kg/ha, 120～135 kg/ha, 75 kg/ha, and 75～90 kg/ha, respectively, can provide sufficient nitrogen for microbial decomposition. The urea application rate for returning 100% wheat straw to the field in Huang-Huai-Hai region, Middle-Lower Yangtze region, Loess plateau region, and Northwest arid region was 135–230 kg/ha, 110–190 kg/ha, 85–145 kg/ha, and 95–165 kg/ha, respectively. 52.5–98.5 kg/ha of urea was used for 100% early rice straw returning to the field in Middle-Lower Yangtze region and South China. In addition, the urea application rate for 100% middle-late rice straw returning to the field was 95–180 kg/ha, 100–185 kg/ha, 95–175 kg/ha, and 75–140 kg/ha, respectively. The rate of urea application for 100% corn straw returning to the field in Northeast China, Huang-Huai-Hai, Northwest arid region, and Southwest China was 60–135 kg/ha, 50–115 kg/ha, 60–135 kg/ha, and 45–105 kg/ha, respectively. The amount of nitrogen fertilizer required for the total return of crop straw is not only affected by crop straw C : N, yield per unit area, and ratio of grass to grain but also affected by straw returning mode, regional nitrogen application level, and other factors. Therefore, the amount of nitrogen fertilizer should be adjusted according to the type of cropping system, soil, and climatic conditions of the specific location. This substantial N input for stimulating straw decomposition may favor N losses with nitrate leaching and nitrous oxide emissions and hold a potential for soil N eutrophication in the long term if the level is not carefully adjusted to the N requirement of the subsequent crops and changes in soil organic matter levels.

The significance of this research is on maize, rice, sorghum, millet, groundnut, soybeans and cowpea straw for stronger sustainability in Ghana’s economic development. Quantifying and re-use of crop straw resources in Ghana is still at the infancy stage hampering the efficient recycling of these resources in a sustainable manner. Sustainability is straw as a renewable resource to improve soils, livestock production, generate renewable energy and reduce pollution for development. The aim of this research was to estimate the crop straw yield from 2006 to 2016 and identify the various utilization modes for major cereals and legumes in Ghana. In addition the distribution of maize, rice, sorghum and cowpea straw across major producing regions was calculated. Results obtained showed that 77,404,709.75 tonnes of cereals and legumes straw were produced in Ghana from 2006 to 2016. Cereal straw recorded a 72.3% yield whilst legume straw recorded 26.8%. Maize and groundnut straw recorded the highest yield of 37,323,264.16 and 12,495,288.96 tonnes respectively. Brong Ahafo region of Ghana had the highest maize straw yield with the Northern region recording readily availability of both cereals and legumes straw resources. The major re-use methods of straw in Ghana are as livestock feed, fertilizer, cooking fuel, for sale and as a substrate for mushroom production. We recommend strategies the government can adapt to develop policies geared towards the accurate recording of straw and their comprehensive utilization in Ghana. The efficient utilization of straw resources will reduce soil erosion, improve soil fertility, serve as feed for livestock, reduce pollution, generate biofuels plus generate employment to benefit the rural economy.

In a previous study, a daily evaporative fraction (EF) parameterization scheme was derived based on day–night differences in surface temperature, air temperature, and net radiation. Considering the advantage that incoming solar radiation can be readily retrieved from remotely sensed data in comparison with surface net radiation, this study simplified the daily EF parameterization scheme using incoming solar radiation as an input. Daily EF estimates from the simplified scheme were nearly equivalent to the results from the original scheme. In situ measurements from six Ameriflux sites with different land covers were used to validate the new simplified EF parameterization scheme. Results showed that daily EF estimates for clear skies were consistent with the in situ EF corrected by the residual energy method, showing a coefficient of determination of 0.586 and a root mean square error of 0.152. Similar results were also obtained for partly clear sky conditions. The non-closure of the measured energy and heat fluxes and the uncertainty in determining fractional vegetation cover were likely to cause discrepancies in estimated daily EF and measured counterparts. The daily EF estimates of different land covers indicate that the constant coefficients in the simplified EF parameterization scheme are not strongly site-specific.

The diurnal cycle of land surface temperature (LST) is an important element of the climate system. Geostationary satellites can provide the diurnal cycle of LST with low spatial resolution and incomplete global coverage, which limits its applications in some studies. In this study, we propose a method to estimate the diurnal cycle of LST at high temporal and spatial resolution from clear-sky MODIS data. This method was evaluated using the MSG-SEVIRI-derived LSTs. The results indicate that this method fits the diurnal cycle of LST well, with root mean square error (RMSE) values less than 1 K for most pixels. Because MODIS provides at most four observations per day at a given location, this method was further evaluated using only four MSG-SEVIRI-derived LSTs corresponding to the MODIS overpass times (10:30, 13:30, 22:30, and 01:30 local solar time). The results show that the RMSE values using only four MSG-SEVIRI-derived LSTs are approximately two times larger than those using all LSTs. The spatial distribution of the modeled LSTs at the MODIS pixel scale is presented from 07:00 to 05:00 local solar time of the next day with an increment of 2 hours. The diurnal cycle of the modeled LSTs describes the temporal evolution of the LSTs at the MODIS pixel scale.