Soil Organic Carbon Build-up and Dynamics in Rice–Rice Cropping Systems

Intensive irrigated rice system is the most important food production system in the world. Continued population growth necessitates increased rice production to meet the increased need of food production through increased rice productivity to ensure food security. In contrast, the recent slowdown in yield growth in intensive irrigated rice‐based cropping systems as a result of deterioration of soil health and decline in productivity level is a serious cause for concern. The objective of this research was to investigate the soil organic carbon (SOC) build‐up and its dynamics in rice–rice cropping system by including a green manure (GM) crop Sesbania rostrata Berm. either during fallow and/or intercrop at 4 : 1 ratio as additive series without changing rice geometry. The results revealed that there is a gradual build‐up of SOC when S. rostrata included and in situ incorporated at flowering stage as a basic means of improving soil quality in rice–rice cropping system. Further, the soil organic matter fractions viz. humic acid and fulvic acid were also improved in all GM‐incorporated systems. In general, the proportion of fulvic acid was higher than humic acid. Cropping system involving three GMs viz. S. rostrata‐rice/S. rostrata‐rice/S. rostrata registered significantly higher SOC and was 10.63 percent higher than traditional rice–rice cropping system (A₁). This was followed by S. rostrata‐rice/S. rostrata‐rice system. Although the traditional rice–rice cropping system (A₁) also conserved SOC (0.29 and 1.69 % higher than initial during first and second annual cropping cycle, respectively), the magnitude was very low. Repeated application of S. rostrata as GM improved SOC, which formed the basis for sustainable management of soil resources. It can be concluded that S. rostrata would affect the rate of loss of SOC in cropping systems and its ultimate level in soils.     

‘Shifting ground’: Renegotiating land rights and rural livelihoods in Sarawak,Malaysia

In this paper, we use an actor‐oriented perspective to explore the nature and extent of conflict and negotiation with regard to land use and tenure among the Iban of Sarawak. The Iban are shifting cultivators who have long been involved in smallholder cash crops. We argue that the complexity of land‐use change and the major shifts in land law and policy in Sarawak in recent decades, particularly those favouring the rapid expansion of oil palm plantations on both state and customary land, have created a situation of indeterminacy that can be exploited to renegotiate land rights and livelihoods. We present a case history of an Iban community that has ‘shifted ground’ several times over the past century, both geographically and in its strategic position relative to state and private sector actors. We show how, under formidable pressure from these actors, this community has nevertheless renegotiated its access to land and other resources, and opportunistically developed a diversified livelihood system that has enabled it to survive in rapidly changing political and economic conditions. While not necessarily typical, the case sheds light on the limits and modes of negotiability in the context of a strong developmental state.     

耕地生产潜力研究——以新郑市为例

为了提高新郑市土地资源利用水平,采用机制法的逐步订正模型对新郑市的耕地生产潜力进行定量估算;用耕地生产力指数模型中的PI指数作土壤修正系数对气候生产潜力做修正;用生产潜力指数,对耕地生产力水平进行评价。结果表明：新郑市的平均土壤修正系数为0.54;平均生产潜力为19393.84 kg/hm²;平均生产潜力指数为47.39%,因此新郑市尚有较大的耕地生产潜力有待开发。     

Comparative Performance of Rice with System of Rice Intensification (SRI) and Conventional Management using Different Plant Spacings

The System of Rice Intensification (SRI) reportedly enhances the yields of rice (Oryza sativa L.) through synergy among several agronomic management practices. This study was conducted to investigate the effects on rice plant characteristics and yield by comparing the plants grown with different methods of cultivation – SRI vs. recommended management practices (RMP) focusing on the impact of different plant spacings. Performance of individual hills was significantly improved with wider spacing compared with closer‐spaced hills in terms of root growth and xylem exudation rates, leaf number and leaf sizes, canopy angle, tiller and panicle number, panicle length and grain number per panicle, grain filling and 1000‐grain weight and straw weight, irrespective of whether SRI or RMP was employed. Both sets of practices gave their highest grain yield with the spacing of 20 × 20 cm; however, SRI yielded 40 % more than the recommended practice. At this spacing, canopies also had the highest leaf area index (LAI) and light interception during flowering stage. The lowest yield was recorded at 30 × 30 cm spacing under both the practices, as a result of less plant population (11 m^?2), despite improved hill performance. During the ripening stage, hills with wider spacing had larger root dry weight, produced greater xylem exudates, and transported these towards shoot at faster rates. These features contributed to the maintenance of higher chlorophyll levels, enhanced fluorescence and photosynthesis rates of leaves and supported more favourable yield attributes and grain yield in individual hills than in closely‐spaced plants. Moreover, these parameters further improved in SRI, apart from the enhanced percentage of effective tillers and showed substantial and positive impacts on grain yield (17 %) compared with recommended practice. In conclusion, wide spacing beyond optimum plant density, however, does not give higher grain yield on an area basis and for achieving this, a combination of improved hills with optimum plant population must be worked out for SRI.     

Dense planting with less basal nitrogen fertilization might benefit rice cropping for high yield with less environmental impacts

Dense planting and less basal nitrogen (N) fertilization have been recommended to further increase rice (Oryza sativa L.) grain yield and N use efficiency (NUE), respectively. The objective of this study was to evaluate the integrative impacts of dense planting with reduced basal N application (DR) on rice yield, NUE and greenhouse gas (GHG) emissions. Field experiments with one conventional sparse planting (CK) and four treatments of dense planting (increased seedlings per hill) with less basal N application were conducted in northeast China from 2012 to 2013. In addition, a two-factor experiment was conducted to isolate the effect of planting density and basal N rate on CH₄ emission in 2013. Our results show that an increase in planting density by about 50% with a correspondingly reduction in basal N rate by about 30% (DR1 and DR2) enhanced NUE by 14.3–50.6% and rice grain yield by 0.5–7.4% over CK. Meanwhile, DR1 and DR2 reduced GWP by 6.4–12.6% and yield-scaled GWP by 7.0–17.0% over CK. According to the two-factor experiment, soil CH₄ production and oxidation and CH₄ emission were not affected by planting density. However, reduced basal N rate decreased CH₄ emission due to it significantly reduced soil CH₄ production with a smaller reduction in soil CH₄ oxidation. The above results indicate that moderate dense planting with less basal N application might be an environment friendly mode for rice cropping for high yield and NUE with less GHG emissions.     

覆盖旱种对水稻产量与品质的影响

以超级稻武粳15(粳稻)和两优培九(籼稻)为材料,从移栽至成熟进行覆膜旱种(PM)、覆草旱种(SM)和裸地旱种(NM)处理,以水种(TF)为对照。结果表明,与TF相比,旱种水稻产量都有不同程度的降低,NM、PM和SM的减产率分别为38.7%～46.5%,9.8%～17.4%和1.7%～7.0%,NM和PM的产量与TF有显著差异,SM的产量与TF差异不显著。SM改善了稻米的加工品质、外观品质和蒸煮品质,NM和PM则降低了稻米这些品质;SM还提高了稻米的最高黏度和崩解值,降低了消减值,NM和PM的结果则相反。两品种的结果趋势一致。SM提高了灌浆期的根系氧化力、叶片光合速率和籽粒中蔗糖-淀粉代谢途径关键酶活性,NM和PM则降低了上述生理指标值。在SM条件下,结实期较高的根系活力、叶片光合速率和籽粒中蔗糖-淀粉代谢途径关键酶活性是获取较高产量和较好稻米品质的重要生理原因。     

不同栽培模式对早稻—再生稻头季稻籽粒灌浆特性和ATP酶活性的影响

为了揭示不同栽培措施对再生稻产量的影响,阐明超高产栽培模式实现高产的生理原因,采用超高产栽培模式并以常规栽培模式作为对照进行比较试验,研究不同栽培模式下早稻—再生稻头季稻籽粒灌浆特性和ATP酶活性的变化。结果表明,与常规栽培模式相比,超高产栽培模式头季稻强、弱势粒的生长潜势强,灌浆最大生长速率出现的时间早,灌浆速率在整个灌浆期的前、中、后3个阶段均较高,活跃灌浆时间较短,强、弱势粒较早进入灌浆盛期,同时,整个灌浆期头季稻强、弱势粒的Mg2 -ATP和Ca2 -ATP酶活性超高产栽培模式也都较常规栽培模式的高,尤其是在籽粒灌浆的快速增长阶段,超高产栽培模式的明显高于常规栽培模式,因而其头季籽粒灌浆呈现出灌浆起动快、灌浆强度大、灌浆后期“拉力”足的特点,从而有利于有机物质向穗部运输,这是超高产栽培模式头季实现大穗、多穗、粒饱、结实率高的籽粒灌浆特性和生理原因。     

川东南冬水田杂交中稻进一步高产的栽培策略

以18个杂交中稻组合为材料,研究了川东南冬水田杂交中稻进一步高产的策略及其栽培技术。结果表明,根据该地区日照条件差的生态特点,采用稀植足肥促进扩“库”增“源”的高产栽培策略,即通过超稀植降低苗峰,改善群体光照条件,提高成穗率,适当降低有效穗数,大幅度提高每穗着粒数,在保持高产适宜叶面积指数条件下扩大库容量;增施氮肥补充光合源,保证在高粒叶比情况下有较好的籽粒充实度。核心技术是栽秧9.0万穴 hm^-2、施氮210 kg。2004年、2005年生产示范分别比传统高产栽培技术增产11.86%~18.31%和14.32%~17.76%,其中超高产田经四川省科技厅组织同行专家现场验收,产量高达10.81~11.05 t hm^-2,创该生态区杂交中稻高产历史纪录。     

基于土地整治的采煤区生态服务价值评价

以采煤沉陷区为研究对象,分析采煤沉陷区土地利用和损毁情况,并通过生态系统服务价值(ESV)指标对土地整治效果进行评价。结果显示,通过土地整治工程,耕地面积由220.24 hm2增至311.08 hm2;采煤沉陷区总生态服务价值属于正向变化,由整治前的348.03×104元/年,增加至到整治后的356.67×104元/年;采煤沉陷区各单项生态服务价值有正向的,也有负向的。其中,属于正向影响的有气候调节、水源涵养、废物处理、食物生产和原材料;属于负向影响的有气温调节、土壤形成与保护、生物多样性保护和娱乐文化。土地整治改善农业基础设施条件和修复并重构生态环境,进而增加社会经济效益和生态效益。     

长沙县基于土壤养分状况的水稻适宜性评价

湖南省是中国重要的双季稻产区,土壤状况直接影响到水稻的生产与区域布局,通过对长沙县主要类型水稻土基本养分状况调查分析,为配方施肥提供依据;将耕地依据水稻种植适宜性进行分类,为长沙县水稻生产区域布局提供技术支持。对长沙县主要的50余种类型稻田土壤进行取样分析其基本理化性状。结果表明,全县水田土壤pH平均含量为5.34;有机质含量平均31.53 g/kg。碱解氮含量平均151.64 mg/kg,有效磷平均含量为21.84 mg/kg,速效钾平均含量为84.01 mg/kg,缓效钾平均含量为198.89 mg/kg根据土壤养分状况,对全县土壤水稻适宜性进行分析,全县高度适宜、适宜、基本适宜的稻田面积分别占水田面积的55.46%、21.25%、19.49%,不适宜仅为3.79%,说明长沙县的土壤状况较适合水稻的生产。     

Marker‐assisted breeding for improvement of anaerobic germination in japonica rice (Oryza sativa)

Direct seeding is increasingly being practiced in rice cultivation areas because it saves labour and reduces cost of production and management. In this study, four japonica‐type breeding lines were developed from a cross of a japonica cultivar and an AG‐tolerant donor, KHO, using marker‐assisted selection. Validation of the target genes AG1 and AG2 in the selected lines was examined by PCR analysis and the background recovery rate by the recurrent parent was confirmed by genotyping using a 6K SNP chip. Compared to the recurrent, the survival rates of the selected lines were improved in a range from 33% to 115% in three conditions; in particular, the survival rate was increased in more than twice that of the recurrent parent under the hypoxic condition. The main agronomic trait, yield and quality‐related traits were similar to those of the recurrent parent. The use of these lines will contribute to the expansion of the cultivation area due to the proven economic benefits of direct seeding in Korea.     

秸秆覆盖对坡耕地土壤性状和马铃薯产量的影响

通过田间试验研究稻草和玉米秸秆覆盖对坡耕地土壤侵蚀、土壤水分、土壤温度、土壤小动物种类和数量、杂草生长及马铃薯产量的影响。结果表明：坡耕地秸秆覆盖栽培秋马铃薯能减少土壤泥沙流失57.1%~71.4%,有效降低地面秋冬季节极端温度,提高土壤渗蓄保墒能力,增加土壤生物多样性和数量,特别是蚯蚓的数量明显增加,比对照高2倍以上,稻草和玉米秸秆杂草量仅为对照的9%~57%,马铃薯产量增幅为33%~77%,增产效果明显。因此,坡耕地稻草和玉米秸秆覆盖有利于保蓄水土,改良土壤性状,稳定提高马铃薯产量。     

水稻旱直播栽培发展现状、问题及应用前景

粮食安全是世界各国关注的重要课题。水稻生产在粮食安全中起着重要作用,而传统水稻种植与水资源紧缺、劳动成本高等矛盾日益突出。水稻旱直播栽培技术越来越得到各国研究者高度重视。本文分析了国内外关于水稻旱直播栽培的发展研究现状,表明水稻旱直播栽培具有省工、节水、便于机械化种植,能提高水肥利用率及降低劳动成本等特点与优势,同时也指出该种栽培方式存在杂草和倒伏问题较难控制、对田间管理要求较高及稻米品质较差等不足,提出水稻旱直播栽培技术可以缓解我国水资源紧缺情况,提高水稻生产效率,对保障我国粮食安全起重要作用,在我国水稻生产中具有广阔的应用前景。     

Property rights for social inclusion: Migrant strategies for securing land and livelihoods in Papua New Guinea

This paper examines the broad range of informal land transactions and arrangements migrants are entering into with customary landowners to gain access to customary land for export cash cropping in the oil palm belt of West New Britain, Papua New Guinea. Whilst these arrangements can provide migrants with relatively secure access to land, there are instances of migrants losing their land rights. Typically, the land tenure arrangements of migrants with more secure access to land are within a framework of property rights for social inclusion whereby customary landowners’ inalienable rights to land are preserved and the ‘outsider’ becomes an ‘insider’ with ongoing use rights to the land. Through socially embedding land transactions in place‐based practices of non‐market exchange, identities of difference are eroded as migrants assume identities as part of their host groups. This adaptability of customary land tenure and its capacity to accommodate large migration in‐flows and expanding commodity production undermines the argument common amongst proponents of land reform that customary tenure is static and inflexible. Before such claims are heeded, there must be more detailed empirical investigations of the diverse range of land tenure regimes operating in areas of the country experiencing high rates of immigration.     

Field-specific variable rate fertilizer application based on rice growth diagnosis and soil testing for high quality rice production

This study was carried out to verify the applicability of variable rate fertilization (VRF) based on soil testing and diagnosis of rice plant growth for high quality rice production of var. Chucheongbyeo at the farm level. The field trials were conducted at Icheon in Gyeonggi province on a 10 ha farm consisting of 45 experimental fields. For comparative study, 15 field trials were carried out adopting fertilizer management (FPM) practices currently used by farmers. FPM fields were managed by each rice grower using current cultivation methods, but in each VRF field fertilizer application was prescribed using soil test results and the amount of N fertilizer for top-dressing at panicle initiation stage was calculated using rice growth value at that stage. In VRF fields, the total amount of N fertilizer application was less (72 kg ha⁻¹) than that in FPM fields (103 kg ha⁻¹). However, the amount of K₂O fertilizer application was more in VRF fields (60 kg ha⁻¹) than that in FPM fields (52 kg ha⁻¹). The amount of P₂O₅ fertilizer application was similar between the VRF and FPM fields. Plant height was significantly shorter and the number of tillers was significantly more at VRF fields than at the FPM fields. Coefficient of variation (CV) of each growth characteristic measured in VRF was lower than that of FPM fields at panicle initiation stage. There was no difference in culm and panicle length and panicle number between them at the grain filling stage, but CV of panicle numbers per m² decreased in VRF compared with that of the FPM fields. Rice yield was not different between VRF and FPM fields despite higher brown rice recovery and 1,000-grain weight in VRF fields. Under VRF management, head rice yield increased due to an increase in head rice ratio accompanied by a reduction in brown rice protein content and variation of quality characteristics. These results suggest that VRF application based on soil tests and measurement of rice growth value at panicle initiation stage has the potential for quality control and production of high quality rice through increasing uniformity of growth and reducing the variability in quality among individual fields.     

Modelling rice competition with <Emphasis Type="Italic">Echinochloa crus-galli</Emphasis> and <Emphasis Type="Italic">Eleocharis kuroguwai</Emphasis> in transplanted rice cultivation

Field experiments were conducted to investigate rice — Echinochloa crus-galli and rice — Eleocharis kuroguwai competition under transplanted rice cultivation in four major rice production areas; Suwon, Daejeon, Iksan, and Naju in Korea. Rice yield data were used to predict rice yield as a function of plant densities of E. crus-galli and E. kuroguwai using a rectangular hyperbola and to determine economic threshold (ET) levels of the weeds. Both weed species significantly reduced number of tillers at early rice growth stage, resulting in significant reduction in number of spikes, and the other yield components such as number of grains, maturity and 1,000-grain weight at later growth stage. The weed competitivity represented by parameter ranged from 0.0145 to 0.0346 for E. crus-galli and from 0.0037 to 0.0187 for E. kuroguwai, indicating that the competition effect of E. crus-galli on rice yield was slightly greater than that of E. kuroguwai. The ET values of E. crus-galli were between 0.298 and 1.078 plants m⁻², while those of E. kuroguwai were between 0.848 and 5.298 plants m⁻², depending on weed competitivity and herbicide price. Therefore, our results can be used to support decision-making on herbicide application for E. crus-galli and E. kuroguwai management in transplanted rice cultivation.     

A family business: Women,children and smallholder sugar cane farming in Fiji

Abstract: This paper highlights the contribution of women and children to the sugar industry in Fiji by examining the importance of family labour in the historical development of the smallholder system and describing the present situation for the study participants. It is based on ethnographic fieldwork conducted during 1996–97, on the island of Vanua Levu in the northern region of Fiji. The twenty smallholder households in the study comprised both Fijian and Fiji Indian respondents who relied primarily on selling sugar cane for their cash income. How inequalities within the household in terms of allocation of labour and resources are legitimated is outlined. Resource distribution within the household in regards to two important issues for the sugar industry, land and trade liberalisation, are examined. In light of global trends in trade liberalisation and probable falls in sugar prices, future strategies for survival identified by Fijian and Fiji Indian smallholders are also discussed. The case study demonstrates that the sugar industry is still largely reliant on family labour and, particularly for low socio‐economic smallholders, the unremunerated labour of family members makes an essential contribution to the production of sugar cane.     

闽北中低产田土壤主要障碍因素分析

南平市是福建省的粮食主产区,耕地面积为22.05万hm²,其中水田21.33万hm²。以单位面积产量水平划分,有71.74%为中低产田。这些中低产田是制约粮食生产进一步发展的关键所在,也是提高单位面积产量和增加粮食总产的潜力所在。笔者通过分析不同类型中低产田的主要土壤障碍因素和肥力特性,总结经过实践可行的工程措施及农业生物技术措施,旨在为2015—2018年抛荒山垄田复垦改造及今后中低产田治理提供科学依据。     

镇域内土地动态变化及与农民收入的关系研究——-以湖北省宜都市红花套镇为例

利用差分GPS在乡镇内采集324个土样,通过对土壤养分特性的分析,结合研究区土地利用的动态变化,与人均收入之间建立回归方程,为当地种养殖业发展提供决策服务,具有较好的实用性和创新性。 研究区土壤养分指标中,碱解氮的变异系数最小为25.6%;土壤有效磷的变异系数最大,变异值达到了95.9%;而土壤速效钾的变异系数79.0%居中;经正态分布检验,研究区土壤养分的空间相关性减弱,朝均一化发展,这说明了红花套镇土地养分变化受人为因素影响较大,当地的土壤适合并已形成大面积的发展种养殖业,传统的稻、麦、棉种植数量和产量都与红花套镇的人平纯收负相关,对当地人平纯收贡献最大的是柑桔总产,相关系数分别为0.822、0.966,土地利用效率最大的是水产品养殖,相关系数分别为-0.760、0.870。     

Factors affecting variation in farm yields of irrigated lowland rice in southern-central Benin

For increasing rice production in West Africa, both expansion of rice harvested area and raising rice yield are required. Development of small-scale irrigation schemes is given high priority in national rice development plans. For realizing potential of the newly developed schemes, it is essential to understand yield level, farmers’ crop management practices and production constraints. A series of field surveys were conducted in six small-scale irrigation schemes in Zou department, Benin during the dry season in 2010–2011 to assess variation in rice yields and identify factors affecting the variation. The schemes were established between 1969 and 2009. Rice yields ranged from 1.3 to 7.8 t ha⁻¹ with an average yield of 4.8 t ha⁻¹. The average yield was only 2.9 t ha⁻¹ for newer irrigation schemes developed in 2002 and 2009. Multiple regression analysis using farmers’ crop management practices as well as abiotic and biotic stresses as independent variables revealed that 75% of the variation in yields could be explained by five agronomic factors (fallow residue management, ploughing method, water stress, rat damage and N application rate) and two edaphic factors (sloped surfaces and sand content in the soil). Removing fallow residue from the fields for land preparation reduced yields. Yields were lower in plots ploughed by hand than by machine. Sloped surface, water stress and rat damage reduced yields. Yield increase due to N application ranged from 0.8 to 1.6 t ha⁻¹. Higher sand content was associated with lowered yields. The low yields in new irrigation schemes caused by sub-optimal crop management practices suggest that farmer-to-farmer learning and extension of good agricultural principles and practices can increase yields. Organizational capacity is also important to ensure the use of common resources such as irrigation water and tractors for land preparation.