Simei ZHANG, Sijun YANG, Zuliang SHI, Zhizhou CHANG

Institute of Agriculture Resources and Environment, Jiangsu Academy of Agricultural Sciences; Key Laboratory of Agri-environment in Downstream of Yangtze Plain, Ministry of Agriculture, Nanjing 210014, China

As the residue of crops after harvesting,straw contains various nutrient elements needed for crop growth. Thus, straw recycling can increase soil fertility and carbon sequestration, and improve soil structure[1]; at the same time, for its rich fiber organic matter,it can be used not only as ruminant feed, base stock of edible fungi cultivation, raw materials of panel, wall materials and biodegradable container, but also as raw materials of biomass energy[2].Therefore, straw returning to field or utilization off the ground can change"waste" into valuables, thereby effectively reducing or even eliminating the adverse effects of straw optionalburning. Straw utilization off the ground has many utilization ways and high potential value,however,its large quantity of resource[3],wide distribution range, low stacking density and difficult straw collection restrict straw utilization off the ground. Xing Aihua et al.[4]analyzed the cost, energy consumption and environmental influence in the collection process of straw biomass resources,and found that the purchase cost of straw accounted for 36.99% of total cost in the collection process, transportation (uncompressed)cost accounted for 37.31%of total cost, and compress can reduce the transportation cost,thereby slightly reducing the total cost. MITRA et al.[5]analyzed the generating cost of Thai straw, and believed that the cost of collecting and transporting low density straw were high, which greatly increased the cost of fuel for power generation. Feng Wei et al.[6]thought that high cost of collection, storage and transportation as well as imperfect related systems were key factors restricting large-scale use of straw.

Jiangsu Province is the largest and the most representative ricewheat double cropping area in the south of China,and its area of planting region is about 160×104hm2,which accounts for more than 70% of rice and wheat planting area. In recent years,affected by social and economic development and restricted by the lack of rural labor, the planting pattern of late maturity of rice and later sowing of wheat was formed, the cohesion contradiction of crops for rotation has become increasingly conspicuous, thus the difficulty of rice and wheat straw collection increased obviously. To know the difficulties and key points in the collection process of straw, a case study of rice and wheat straw collection in Jiangsu Province was conducted using questionnaire survey and field research, the difficulties faced by straw collection were analyzed taking into account the meteorological data of rice and wheat harvesting seasons in the region, so as to provide a beneficial thinking for breaking through the bottleneck of straw collection and establishing the collection-storage-transportation system.

Investigation Methods

In 2012,questionnaires were given out to agriculture technology and popularization center (station) of 52 counties (cities)to investigate the soil preparation and sowing condition after rice and wheat harvest, and then 41 effective questionnaires were obtained. At the same time, the field research was carried out in 2 townships respectively in Nanjing and Suqian,namely township A and township B,so as to know the difficulties of peasant households in straw collection, and 322 effective investigation results were got.The general information of investigated townships was as follows: The population of township A was 33 882,and its land area and agricultural acreage were respectively 5 680 and 2 829 hm2, the cultivated areas of rice and wheat were respectively 2 773 and 1 848 hm2and the average yields per unit area were respectively 9 045 and 4 875 kg/hm2; the population of township B was 28 466, and its land area and agricultural acreage were respectively 8 436 and 4 867 hm2, the cultivated areas of rice and wheat were respectively 2 700 and 4 700 hm2and the average yields per unit area were respectively 7 700 and 5 700 kg/hm2.

Results and Analyses

Status of rice and wheat straw collection

The investigation results of 2 townships showed that the main handling ways of rice and wheat straw were:directly returning to field, collection and utilization, accumulation and abandonment, as well as uncontrolled burning (including burning after busy season), and the straw collection was often used as living fuels, animal feed,marsh gas and power generation materials,etc.The peasant households of straw returning from townships A andB respectively occupied 22.01% and 28.75% of investigation households,these of collection and utilization respectively occupied 60.02% and 15.00%, these of accumulation and abandonment respectively occupied 17.07%and 33.75%,and these of uncontrolled burning respectively occupied 0.90% and 22.50%. Aboved data of the two townships showed that the main handling way of rice and wheat straw was directly returning to field.The proportion of the households of rice and wheat straw collection and utilization of township A was greatly more than that of township B, moreover, most of the straw was used as living fuels. Based on the survey data,it can be seen that part of rice and wheat straw in the two townships had not been effectively handled, more than half of households’ rice and wheat straw from township B had not been used, the proportion of discard and burning reached more than 55%,which was greatly higher than that of township A. Thus, there were greater differences on the handling methods of straw and collection and utilization in the two townships,which may be related to local social economic development level, social environment and peasant households’ living habit, etc.Furthermore, the difficulties encountered in the straw collection and utilization were collection, storage and transportation, etc.,which was the key to break through the bottleneck of the straw utilization off the ground.

Table 2 The precipitation and rain frequency of rice and wheat in the harvest season in different regions of Jiangsu

Difficulties encountered in rice and wheat straw collection

Short collection time Rice-wheat double cropping was the main farming system ensuring the food security of Jiangsu Province.The planting pattern of late maturity of rice and later sowing of wheat was not only bad for the sustainable increase of rice and wheat yield, but also shortened the collection time of straw. The questionnaire survey results of 41 counties (cities)showed that the concentrated harvest time of rice in Huaibei, central Jiangsu and South Jiangsu was mainly from middle and late October to early and middle November, and the latest harvest dates of the three regions were respectively on December 5, November 20 and December 5; the concentrated harvest area of rice in Huaibei,Central Jiangsu and South Jiangsu respectively accounted for 83.67% ,79.11% and 85.66% of the cultivated area. The crop after rice harvesting was mainly wheat, and the cultivated area of wheat accounted for 86.02%of total crops planted. The suitable sowing time of wheat in Huaibei, Central Jiangsu and South Jiangsu was separately in early-to-middle October, late October and early November,all these were in the the concentrated harvest time or even before the harvest time of rice,indicating that the suitable sowing time of wheat was missed after the harvest of rice.

The harvest days of wheat in Huaibei, Central Jiangsu and South Jiangsu were mainly 3-10 d,the latest harvest dates of the three regions were respectively on June 25,June 15 and June 20, and the concentrated harvest area of wheat all accounted for more than 80% of the cultivated area.The crop after wheat harvesting was mainly rice, and the cultivated area of rice accounted for 75.89% of total crops planted. The suitable sowing time of rice in North Jiangsu, Central Jiangsu and South Jiangsu was separately in early-to-middle June, middleto-late June and late June/early July[7].Based on rice direct sowing, the optimum sowing period of medium maturing mid-season japonica early rice was from June 7 to June 17, and the latest date was on June 20,that of the southern regions along Huaihe River was before June 5,and that of Central Jiangsu Region was before June 10 and the latest date was on June 15;the sowing time of late maturing midseason japonica rice of the northern regions along the river was before June 15; and that of early-maturinglate-season Japonica rice of South Jiangsu was also before June 15.From the above data, it was shown that the harvest time of wheat and the suitable transplanting or sowing time of rice almost overlapped completely.

In conclusion, the harvest time of rice and wheat was relatively concentrated, rice and wheat straw greatly generated in a short time,and the harvest time of rice and wheat overlapped. Thus the collection time of straw was very short, especially in the harvest season of wheat,and the season contradiction was very serious.

Great effect of weather The precipitation and rain frequency of rice and wheat in the harvest period in different regions of Jiangsu were analyzed using the monitoring data of 30 a of multiple meteorological stations in Jiangsu Province.The results(in Table 2) showed that the ten-day precipitation during rice and wheat harvest seasons (from late May to early December) was among 7.21-87.28 mm, the ten-day precipitation days were among 1.53-5.00. Precipitation weather not only affected the punctual harvest of rice and wheat,but also greatly affected straw collection and baling, transportation and storage.

Taking the case of township B,the precipitation in the harvest season of rice and wheat was excessive, especially the rain frequency in the harvest season of wheat was high and the rainfall was great, which objectively increased the difficulty of straw collection. Although the precipitation and rain frequency in the harvest season of rice were both less than these of wheat in the harvest season, the drainage of rice field was difficult and soil moisture content was high, which certainly affected the field work of straw collection machine, straw collection and baling. KADAM et al.[8]thought that only when the soil humidity was less than 31% would the straw be suitable for collection and baling; if the moisture content of rice straw was more than 50%, except for the direct silage of straw as ruminant feed, all other utilization modes needed to follow the collection and storage of straw after air drying. HORSFIELD et al.[9]showed that only when the moisture content of straw was less than 25%can effectively avoid the fermentation and mass propagation and pollution of mycete in the storage process of straw. Therefore, to make effective storage of the collected straw,it would take an adequate period of time to dry,so as to reduce the moisture content to the optimal level, which would greatly shorten the effective collection time of rice straw.

Table 3 Comparison on the efficiency of different straw balers

Low collected efficiency The investigation results of the will of straw collection and utilization of township B showed that 31.25% peasant households thought that the collected efficiency was too low, 21.25% of them thought that the farm work was too busy,21.25%of them thought that the labor force was insufficient, 13.75% of them thought that straw collection was troublesome and the treatment cost was high,and 12.50%of them thought that there was lack of straw sale market. The collection methods, cost and efficiency of straw were further investigated and analyzed, and found that the actual income of each vehicle was about 60 RMB under the premise of ignoring the straw cost, using the methods of labor collection, labor loading and unloading, walking tractor transport, and deducting the costs of fuel consumption and machinery depreciation,2-3 vehicles can be transported each day by two cooperation, thus the earnings of straw collection and transportation was 60 -90 RMB/d, which was lower than income of migrant workers.Wang Xiaoli et al.[10]analyzed the cost and benefit of straw baling and collection, and found that even if subsidies for purchasing baling and transportation machinery were offered,the cost of baling and transportation also reached 750 RMB/hm2, however,the cost of baling and collection of straw was just 720 RMB/hm2.The survey results of Mei Fuchun[11]and Ma Ji et al.[12]also showed that it was difficult to attract social capital input straw collection because of low benefit of.Thus,in the circumstances of low benefit,busy farming season and the transfer of a large number of rural labor forces,dispersing farmers can not be the main part of straw collection.

What’s more, the survey results of township A indicated that the proportion of straw handling by governments or enterprises was low, namely the the proportions of rice and wheat straw handling by governments or enterprises were 5.31% and 9.93%, respectively. In field research, many peasant households expressed their expectations for government’s organization, and held that since the government ordered the prohibition of straw burning, it should shoulder the responsibility of organizing the straw handling. In addition, according to peasant households, the straw handled by government also had not been used effectively,it only be stacked concentratedly,letting it decay.

Low level of mechanization The mechanization level of of straw collection was low. First, the equipment of straw collection was sparse. Straw baling machine can hardly satisfy actual requirement, thus it can not accomplish the task of strw baling and collection of mass rice and wheat straw.Second,it was needed to improve and perfect the existing equipment and technology of straw collection. Domestic pick-up balers had the deficiencies of poor stability of continuous operation, high fault rate and low efficiency,etc.,which directly affected the efficiency of straw collection. The survey results of operation efficiency of straw balers (Table 3) showed that a domestic baler can totally collect straw on 40-60 hm2field within effective collection time in single season.That is tosay, the township with thousands of hm2needed tens of balers. Furthermore, there was not whole set of equipment for loading, unloading,stacking and transporting. The transport of straw was mainly three-wheel agrimotor or tractor, so the transport efficiency was not high.

Taking the case of township B,there were totally 3 sets of pick-up balers. The work efficiency of a single machine was 5.70 hm2/d.If there were 10 consecutive days, straw of 171.00 hm2field can be collected, which was only 3.51% of total cultivated area in the township, thus the existing straw balers can not meet the actual requirement.The transportation machine was mainly walking tractor, although the quantity was sufficient and can be competent to the task of straw transportation, the transport efficiency was low.

Countermeasures and Suggestions

Promoting the driving force of straw collection efficiency

At present, although some local governments have formulated some preferential policies of straw utilization,such as straw turnover subsidy, straw granulating subsidy(according to electrofarming), agricultural implements subsidy, sale price subsidy of straw power plant, etc., and some districts and counties in South Jiangsu even have offered subsidies for straw collection, the coverage of straw subsidy policy generally was not wide, the systematicness was not strong, the interest ties were not tight, the incentive mechanism of policy was imperfect,the enthusiasm of straw collection of social capital investment was not high,and the leading and key enterprises of straw utilization were few. It was suggested to set up the subsidy (compensation)mechanism for straw terminal consumers, and the formulation of subsidy (compensation) standard should consider the fluctuation of market price.For example,the straw granule (block) was mainly provided to boiler users as fuel replacing coal,calculating by calorific value, 2 t straw granule (block) was equivalent to 1 t standard coal, but the market price of standard coal was wavelike, so only formulating rational straw granule(block)would boiler users continuously use straw granule (block) as the fuel,straw collection enterprises can make a profit, thereby ensuring the effective and long-term operation of straw collection and utilization.Secondly,due to the fluffy straw and large floor space of straw stocking and storing, it was suggested to formulate the priority and preferential policy of straw stocking and storing land, so as to ensure the economy and safety of straw stocking and storing. In addition, the transport licensing system for straw transport vehicle was suggested to establish,so as to ensure the express, safe and low-cost transport of straw.

Accelerating the research and development of rice and wheat harvest-baling machine

With the continuous acceleration of industrialization and urbanization, a large number of rural labor force has transferred to the urban, thus it is impossible to collect straw by manpower in the harvest and sowing seasons of rice and wheat, so straw collection by machine has become the inevitable choice. At present, the pick-up balers produced in domestic have been mainly from the improvement of foreign pull-type pick-up balers of straw. The straw must be aired in the field until the moisture content was less than 25%before the picking up and baling. In extensive production, the time between one crop harvest and the other crop sowing was short, which is not enough to air straw in the field, which greatly affected the baling and collection of rice and wheat straw in rice and wheat rotation areas. To alleviate the contradiction between straw collection and crop planting, and avoid working many times with machines, DOBIE et al.[13]put forward total harvest of rice, namely the whole rice plant was harvested firstly, and then separated outside the field. Zhao Aidong et al.[14]combined the mechanization harvest with baling of rice and wheat in 2006,and realized the institutional operation of rice and wheat harvest and straw baling. Hereafter, many scholars put forward the institutional operation designing scheme of rice and wheat harvest and and straw baling in succession.Shandong Changlin Construction Machinery Co., Ltd. developed a harvest baler in 2012,which can complete a one-time processing of rice and wheat harvest and straw baling operation, reaching the aims of saving labor and reducing cost. However, because of the short time of harvest-baling machine developed, there were many problems like poor stability and low efficiency.In order to solve the cohesion contradiction between rice and wheat straw collection and crop rotation, and alleviate the soil structure failure caused by machine going to the field many times, as well as solve the extremely urgency of straw,the research and development efforts and progress of rice and wheat harvest-baling machine should be strengthened and quickened. Meanwhile, the transport vehicles with the function of field wafer should also be developed, so as to realize the whole course mechanization of straw baling collection and transportation.

Establishing a long-effective mechanism of straw collection

It was be explicitly stipulated in The Prohibition of Straw Burning and Comprehensive Utilization Management Method in 1999 formulated by Ministry of Environmental Protection of the People’s Republic of China and six ministries and commissions directly under the State Council that the prohibition of straw burning should be under the unified leadership of "local people’s governments at different levels".It was also clearly pointed out in Decision on Promoting the Comprehensive Utilization of Crop Straw by Jiangsu Provincial People’s Congress in 2009 that local people’s governments at different levels are the liability subject promoting the comprehensive utilization of straw and the prohibition of straw burning; it was also proposed in The Prohibition of Straw Burning and Comprehensive Utilization Management Method that the implementation of the prohibition of straw burning should based on township. These required all people's governments to assume the overall planning and organization and coordination responsibilities of straw collection and storage as well as transportation, positively cultivate enterprises or special cooperative or-ganizations as the subject of straw collection, and well plan straw returning to field and collection, so as to ensure the long run of corresponding enterprises; in addition, the governments should give substantial help and support in the purchase of agricultural machinery, straw storage land and straw transportation, thereby truly building a long-term operational mechanism of market-driven and enterprise operation, only this will the straw collection and utilization be practicable and the prohibition of straw burning be continuously and healthily developed.

Acknowledgement

We express deep thanks for the investigation data about the straw utilization of township A provided by Ouyang Xuan, Jiang Hao, Liao Shimiao, Xie Bin, Zhou Feifei, Qian Zhengzong etc. from College of Life Sciences of Nanjing Agricultural University!

[1]ZENG MX(曾木祥),WANG RF(王蓉芳),PENG SQ (彭世琪),et al.Summary of returning straw into field of main agricultural areas in China(我國主要農(nóng)區(qū)秸稈還田試驗總結(jié))[J].Chinese Journal of Soil Science (土壤通報), 2002, 33(5):336-339.

[2]XU Y(徐勇),YONG Q(勇強),YU SY(余世袁).Strategies and measures to construct an effective comprehensive utilization system of crop straw-taking Jiangsu Province as an example (構(gòu)建秸稈高效綜合利用體系的對策與措施:以江蘇省為例)[J]. Biomass Chemical Engineering(生物質(zhì)化學(xué)工程),2013,47(3):11-16.

[3]GU KJ (顧克軍),ZHANG SM (張斯梅),XU B (許博), et al. Estimation of total yield and collectable amount of rice straw in Jiangsu Province (江蘇省水稻秸稈資源量及其可收集量估算)[J].Journal of Ecology and Rural Environment(生態(tài)與農(nóng)村環(huán)境學(xué)報), 2012, 28(1):32-36.

[4]LV C(呂宸),LV JQ(呂建強),WANG GP(王國平), et al. Problems and countermeasures of crop straw collection in our country(我國農(nóng)作物秸稈收集存在的問題及對策)[J]. Modern Agricultural Sciences and Technology(現(xiàn)代農(nóng)業(yè)科技),2012(22):203-204.

[5]MITRA KD, MIRKO B, SHABBIR HG.Logistics cost analysis of rice straw for biomass power generation in Thailand[J].Energy,2011,36(3):1435-1441.

[6]FENG W (馮偉),ZHANG LQ (張利群),PANG ZW(龐中偉),et al.The economic and environmental analysis of crop residues burning and reutilization in China(中國秸稈廢棄焚燒與資源化利用的經(jīng)濟與環(huán)境分析)[J]. Chinese Agricultural Science Bulletin(中國農(nóng)學(xué)通報),2010,27(6):350-354.

[7]ZHANG XH(張旭暉), HUANG YH(黃毓華). Study and application of drought index during the transplanting period of rice in Jiangsu Province(江蘇省水稻移栽期的干旱指數(shù)研究及應(yīng)用)[J]. Chinese Journal of Agrometeorology (中國農(nóng)業(yè)氣象),2000,21(3):19-22.

[8]KADAM KL, FORREST LH, JACOBSON WA. Rice straw as a lignocellu

losic resource: Collection, processing,transportation and environmental aspects[J].Biomass and Bioenergy,2000,18(5):369-389.

[9]HORSFIELD BC,JENKINS BM,BECKER C. Agricultural residue as an alternative source of energy for the Pacific Gas and Electric Company [R].University of California,Davis,USA,1977.

[10]WANG ZL (王小莉), XU B (許斌),ZHANG CY (張春云).Analysis on the cost and benefit of straw baler(秸稈打捆機成本效益分析)[J].Jiangsu Agricultural Mechanization (江蘇農(nóng)機化),2011(2):22-23.

[11]MEI FC(梅付春).Cost-benefit analysis of straw-burning polution (秸桿焚燒污染問題的成本-效益分析——以河南省信陽市為例)[J]. Environmental Science and Management(環(huán)境科學(xué)與管理),2008,33(1):30-32.

[12]MA J (馬驥).The reasons for Chinese farmers to burn straw on field: Costbenefit comparison and the restrictive conditions analysis case of Duliang township, Kaifeng County, Henan Province(我國農(nóng)戶秸稈就地焚燒的原因:成本收益比較與約束條件分析——以河南省開封縣杜良鄉(xiāng)為例)[J].Journal of Agrotechnical Economics (農(nóng)業(yè)技術(shù)經(jīng)濟),2009(2):77-84.

[13]DOBIE JB, PARSONS PS, CURLEY RG.Systems for handling and utilizing rice straw [J]. Transactions of the ASAE,1973,16(3):533-538.

[14]ZHAO AD (趙愛東),JIANG X (蔣曉).Rice and wheat harvest-baling machine (稻麥聯(lián)合收獲打捆機)[P].200620074426.2,2007-07-18.