Mapping Cropland Burned Area in Northeastern China by Integrating Landsat Time Series and Multi-Harmonic Model

Accurate cropland burned area estimation is crucial for air quality modeling and cropland management. However, current global burned area products have been primarily derived from coarse spatial resolution images which cannot fulfill the spatial requirement for fire monitoring at local levels. In addition, there is an overall lack of accurate cropland straw burning identification approaches at high temporal and spatial resolution. In this study, we propose a novel algorithm to capture burned area in croplands using dense Landsat time series image stacks. Cropland burning shows a short-term seasonal variation and a long-term dynamic trend, so a multi-harmonic model is applied to characterize fire dynamics in cropland areas. By assessing a time series of the Burned Area Index (BAI), our algorithm detects all potential burned areas in croplands. A land cover mask is used on the primary burned area map to remove false detections, and the spatial information with a moving window based on a majority vote is employed to further reduce salt-and-pepper noise and improve the mapping accuracy. Compared with the accuracy of 67.3% of MODIS products and that of 68.5% of Global Annual Burned Area Map (GABAM) products, a superior overall accuracy of 92.9% was obtained by our algorithm using Landsat time series and multi-harmonic model. Our approach represents a flexible and robust way of detecting straw burning in complex agriculture landscapes. In future studies, the effectiveness of combining different spectral indices and satellite images can be further investigated.

Energy Budgeting of Paddy-Pulse Cropping System in Bhadrak District of Odisha and Assessment of Emission from Paddy Straw Burning

Energy auditing of an existing production system helps to assess its energy-use and energy efficiency. The average input energy of paddy-black gram (PB) cropping system (19,862.01 MJ.ha-1) was higher than paddy-green gram (PG) (18,972.34 MJ.ha-1) cropping system in Bhadrak, Odisha. Harvesting and transport operation required highest operational energy for PG (35.57%) and PB (41.20%) farms; while, threshing and winnowing consumed the second highest input energy with 21.34% and 22.71% for PG and PB farms, followed by land preparation with 21.87% and 20.10% respectively. Linear regression data of PG and PB systems showed significant effect (p<0.05) of predictors with R2 values of 87.70% and 82.20% for total output energy and grain energy, respectively; confirming a good fit among the data. The output energy of PB cropping system was 13.91% higher than that of PG cropping system. The PB cropping system, with energy utilisation efficiency (EUE) of 10.31 and 11.82, was more energy-efficient than PG system with EUE of 9.32 and 11.01 for “NC” and “C” farms, respectively. The net energy return of PBC farm was highest with 2,04,505.31 MJ.ha-1. Amongst various pollutants emitted from paddy straw burning in Odisha; CO2 (5,51,296.0 Mg.yr-1), CO (13,102.72 Mg.yr-1), and TPM (4,908.80 Mg.yr-1) had highest share. The quantity of major GHGs (N2 O, CH4 ) released into the atmosphere through paddy straw burning was estimated as 26.43 Mg.yr-1 and 453.12 Mg.yr-1, respectively. Use of straw baler can prevent straw burning, and reduce emission from paddy fields by 2805.54 kg.ha-1 of CO2 and 66.69 kg.ha-1 of CO, 5.96 kg.ha-1 of NOx , 24.98 kg.ha-1 of TPM. Alternatively, use of mulcher can also reduce emission from paddy fields by 2924.44 kg.ha-1 of CO2 and 69.51 kg.ha-1 of CO, 6.21 kg.ha-1 of NOx , 26.04 kg.ha-1 of TPM. The cost of operation of a baler and mulcher were 8,617.0 ₹ ha-1 and 2,543.0 ₹ ha-1, respectively. Input energy and energy saved in paddy fields by baler were 820.0 MJ.ha-1 and 16,928.0 MJ.ha-1; and 266.0 MJ.ha-1 and 24,458.0 MJ.ha-1 by mulcher, respectively

Mix Proportion of Lightweight Straw Ceramsite Concrete

To reduce air pollution of straw burning, and also to improve the ratio of straw comprehensive utilization, this paper presents a lightweight concrete with straw based on the mix proportion research. Firstly, the mix proportion of lightweight ceramsite concrete was designed by a volumetric method. Then, a series of lightweight ceramsite concrete mix proportion experiments were conducted to verify the validity of the design and to evaluate the effect of the admixtures on the performance of the concrete. Finally, the lightweight straw ceramsite concrete mix proportion experiments were conducted by adding straw to lightweight ceramsite concrete for studying the impact of the straw amount on the concrete strength and density. The experimental results show that the compressive strength of lightweight straw ceramsite concrete can reach the requirement of engineering application. The concrete strength and density were descended obviously with the increasing of straw amount. It was suggested that the straw amount should be limited in 20% of the concrete volume.

Net Carbon Sequestration Performance of Cropland Use in China’s Principal Grain-Producing Area: An Evaluation and Spatiotemporal Divergence

As cropland possess dual carbon effects of emitting and sequestering, giving full attention to its net carbon sequestration is an effective option for mitigating global warming. By analyzing the carbon cycle of a cropland use system, we develop an inventory for measuring the net carbon sequestration, covering four carbon sources, i.e., agricultural materials, rice fields, soils, straw burning, with the crop carbon sequestration considered. Different from conventional studies that have focused on quantity, in this study, we define net carbon sequestration performance of cropland use (NCSPC) as the ratio of actual net carbon sequestration to an optimal value per unit of cropland. We estimate the net carbon sequestration of cropland use, from 2000 to 2019, for the study area consisting of the 13 principal grain-producing provinces in China. Then, global-SBM is applied to measure the provincial NCSPC; furthermore, the Theil index and convergence test are employed to portray the spatiotemporal characteristics and regional divergence. The results show the following: (1) The net carbon sequestration was 3.837 t per hectare of cropland in the principal grain-producing area, of which the sequestration and the emission were 6.343 t and 2.506 t, respectively. The share of emissions, from largest to smallest, was methane from rice paddies, agricultural materials, straw burning, and soil nitrous oxide. Specifically, cropland use in Henan exhibited the strongest net carbon sequestration, whereas in Hunan it was the lowest. (2) The average NCSPC was 0.774 in the principal grain-producing area, indicating that 22.6% of the net carbon sequestration per unit of cropland remained to be explored under the corresponding production technology and input combinations. Temporally, the NCSPC had an annual change rate of −0.30%, displaying a slowly declining trend. Spatially, the NCSPC evolved from a scattered distribution to blocky agglomeration, eventually presenting a decreasing pattern from north to south. (3) First, the total Theil index increased, and then decreased, indicating that the regional disparity of the NCSPC expanded early but shrank later. From 2011 to 2019, inter-regional disparity took up more in the total. Over time, both the whole region and the subregions obeyed the σ convergence. Unlike the benign trends observed in Zones I and II, the NCSPC values of Zone III converged to a low level. This study aims to provide a theoretical base for emission mitigation and sequestration promotion for cropland use.