Modeling nutrient and water productivity of sorghum in smallholder farming systems in a semi-arid region of Ghana

The CERES-sorghum module of the Decision Support System for Agro-Technological Transfer (DSSAT) model was calibrated for sorghum (Sorghum bicolor (L.) Moench) using data from sorghum grown with adequate water and nitrogen and evaluated with data from several N rates trials in Navrongo, Ghana with an overall modified internal efficiency of 0.63. The use of mineral N fertilizer was found to be profitable with economically optimal rates of 40 and 80 kg N ha⁻¹ for more intensively managed homestead fields and less intensively managed bush fields respectively. Agronomic N use efficiency varied from 21 to 37 kg grain kg⁻¹ N for the homestead fields and from 15 to 49 kg grain kg⁻¹ N in the bush fields. Simulated grain yield for homestead fields at 40 kg N ha⁻¹ application was equal to yield for bush fields at 80 kg N ha⁻¹. Water use efficiency generally increased with increased mineral N rate and was greater for the homestead fields compared with the bush fields. Grain yield per unit of cumulative evapo-transpiration (simulated) was consistently higher compared with yield per unit of cumulative precipitation for the season, probably because of runoff and deep percolation. In the simulation experiment, grain yield variability was less with mineral N application and under higher soil fertility (organic matter) condition. Application of mineral N reduced variability in yield from a CV of 37 to 11% in the bush farm and from 17 to 7% in the homestead fields. The use of mineral fertilizer and encouraging practices that retain organic matter to the soil provide a more sustainable system for ensuring crop production and hence food security.     

Participatory variety development for sorghum in Burkina Faso: Farmers’ selection and farmers’ criteria

Sorghum (Sorghum bicolor (L.) Moench) is the staple crop of Burkina Faso in West Africa where guinea race landraces are grown in low-input cropping systems. National and international breeding programs have had little success in disseminating modern varieties based on high yield potential caudatum or kafir race breeding materials, mostly introduced from other countries. It has been argued that the breeding objectives were not sufficiently oriented towards the farmers’ needs and preferences, and that they did not target the prevailing growing conditions of Burkina Faso. The objectives of the present article are (i) to identify and examine farmers’ selection criteria for sorghum varieties in the Centre-West of Burkina Faso, (ii) to compare these criteria with the breeder's agronomic observations and standard practices, and (iii) to show how the criteria of both farmers and breeders can be effectively integrated into the early stages of a pedigree breeding program. These objectives take into consideration gender differentiation, consistency of selection criteria and the interrelationship of measured quantitative traits, as well as the impact of these traits and criteria on the final selection. The present paper is based on a pedigree breeding program that was carried out over three years (2001–2003) in two villages of Burkina Faso. Options for integrating farmers’ selection expertise with that of the breeders’ were examined. Participatory selection was initiated with 53 F3/F4 progenies in field trials managed by farmers using rating and voting exercises. The breeders measured and analysed the agronomic data while the farmers evaluated a large number of progenies by means of their three most important selection criteria and a general appreciation. Farmers’ initial choices remained consistent in the selection exercises (voting) performed in subsequent years. The farmers’ methods for defining traits turned out to be more multivariate than the breeders’ formal understanding of these same traits. This was especially so for the criteria of grain quality, earliness, and productivity for which the farmers’ definition encompasses factors such as flour yield and stability across environments. However, rating results between farmer groups were variable. A disagreement between female and male ratings was especially found for the grain quality traits. The results clearly show that farmers can effectively select for traits on the basis of progeny and single plants while pursuing specific agronomic aims such as adaption. Subsequent yield improvement schemes will thus be more efficient in terms of selection intensity related to grain yield. The study is showing the way for breeders to adjust their selection criteria to suit the basic needs of small-scale farmer in semi-arid regions of sub-Saharan Africa.     

An opportunity for increasing factor productivity for rice cultivation in The Gambia through SRI

Promising results from an increasing number of field evaluations of the System of Rice Intensification (SRI) conducted in Asia and Africa indicate that African farmers could increase their rice production while lowering costs of operation and reducing the need for water by utilizing its principles and practices. This system relies not on external inputs to raise productivity but on alternative methods for managing rice plants and the soil and water resources devoted to their cultivation. Farmers in sub-Saharan Africa increasingly have to cope with the impacts of adverse climate effects because water shortages and long dry spells during the cropping season are becoming common, even in lowland rice agroecosystems. SRI management practices create both larger rice root systems that make their plants more resistant to biotic and abiotic stresses and more conducive environments for beneficial soil microflora and fauna to flourish. Better plant growth and development result from promoting plant–soil synergies. Controlled fertilizer management experiments conducted with SRI practices in The Gambia have showed that grain production can be significantly increased without higher application of inorganic fertilizer and with less requirement for water. SRI management practices with fertilizer application at the national recommended dose produced a grain yield of 7.6 t ha⁻¹. Water productivity was greatly increased, with 0.76 g of grain produced per kg total water input, compared to 0.10 g of grain per kg of water when the crop was continuously flooded. Recent hikes in fuel prices and consequent rises in input costs are making domestic rice production less attractive and importation even more attractive. Computation of production costs showed that SRI production, not needing heavy applications of fertilizer, is economically cost-effective. Achieving yield increases through ever-higher fertilizer applications is not economically or environmentally viable. SRI management with recommended fertilizer applications produced a net return of $853 ha⁻¹ compared to $853 ha⁻¹ compared to 37 when using farmers’ present low-productivity practices.     

Satellite evidence for yield growth opportunities in Northwest India

Improving crop yields in major agricultural regions is one of the foremost scientific challenges for the next few decades. In Northwest India, the stagnation of wheat yields over the past decade presents a distressing contrast to the tremendous yield gains achieved during the Green Revolution. One commonly proposed way to raise yields is to reduce the often considerable gap between yield potential and average yields realized in farmers’ fields, yet the likely effectiveness of different strategies to close this gap has been poorly known. Here we use a unique, decade long satellite-based dataset on wheat yields to examine various options for closing the yield gap in the south of Punjab. Persistent spatial differences in sowing dates and distance from canal are found to be significant sources of yield variation, with the latter factor suggesting the importance of reliable access to irrigation water for yield improvement in this region. However, the total yield gains achievable by addressing persistent factors are only a small fraction of yield losses in farmers’ fields. The majority of the yield gap is found to arise from factors unrelated to field location, such as interactions between management and weather. Technologies that improve farmers’ ability to anticipate or adjust to weather variations, or that improve stability of genotype performance across different weather conditions, therefore appear crucial if average crop yields are to approach their genetic potential.     

双季杂交稻“肥促水调”栽培技术的应用

选用优势强、品质优的杂交组合,早季中熟搭配晚季迟熟组合,培育壮秧,控制分蘖肥用量,增大后期施肥量,超前搁田控制苗峰,在一定穗粒基础上,实现总粒数、实粒数和经济系数的大幅度提高,从而提高产量．     

Comparing decentralized participatory breeding with on-station conventional sorghum breeding in Nicaragua: I. Agronomic performance

Few studies have assessed the effective gains achieved by collaborative decentralized participatory breeding, in terms of yield and other agronomic traits, in comparison with centralized conventional breeding using the same breeding schemes. Our study concerned an experience of participatory improvement of tortillero sorghum for low-input cropping systems in northern Nicaragua. It set out to compare the effect of two breeding schemes simultaneously managed on-station and on-farm. Two synthetic populations were used as sources of genetic variability. The study was designed to distinguish between three “selection modes”: farmers’ selection on-farm (FoF), breeder’ selection on-station (BoS) and breeder's selection on-farm (BoF). After two selection cycles, we found that FoF selection reduced phenotypic variability as much as BoS selection. In general, BoS selection produced higher-yielding lines under the target on-farm conditions. But FoF selection was more effective in promoting lines with higher values for an index of agronomic suitability (IAS), expressing a better balance between earliness, plant height, grain size and yield. Such genotypes might cope more easily with local environmental constraints and farmers’ preferences. BoF selection did not prove to be effective for either yield or IAS. This research shows the need for close collaboration between farmers and breeders as well as complementarities between the selection phases managed on-farm and on-station, to make breeding for difficult environments fully efficient.     

Productivity and residual benefits of grain legumes to sorghum under semi-arid conditions in south-western Zimbabwe: Unravelling the effects of water and nitrogen using a simulation model

The APSIM model was used to assess the impact of legumes on sorghum grown in rotation in a nutrient-limited system under dry conditions in south-western Zimbabwe. An experiment was conducted at Lucydale, Matopos Research Station, between 2002 and 2005. The model was used to simulate soil and plant responses in the experiment. Sequences of cowpea (Vigna unguiculata), pigeonpea (Cajanus cajan), groundnut (Arachis hypogaea) and sorghum (Sorghum bicolor) were used in the rotations. Legumes accumulated up to 130 kg of N ha⁻¹ which was potentially available for uptake by sorghum in the following season. The APSIM model predicted total biomass, grain and N yields of the legume phase within the experimental error and performed well in predicting sorghum yield and N supplied in the rotation after cowpea and groundnut. The model generally under-predicted sorghum total biomass and grain yield after pigeonpea. Observed patterns of crop water use, evaporative losses during the dry season and re-charge of soil profile at the start of the rainy season were generally well predicted by the model. An assessment of output on sorghum N and water stresses in the rotation indicated that the legume–cereal rotation is more driven by soil nitrogen availability than water availability even under semi-arid conditions. Further legume–cereal rotation analysis using the model will assist in the understanding of other processes in the rotations in dry environments.     

双季早稻氮肥基蘖肥与穗肥不同比例简比试验

以金优2155为材料,设置双季早稻氮肥基蘖肥与穗肥不同比例简比试验。结果表明,氮肥基蘖肥与穗肥比例为5：5的处理产量最高,具有明显的增产效果。     

Residual effect of poultry litter applied to cotton in conservation tillage systems on succeeding rye and corn

The burgeoning poultry industry in the southeastern US is presenting a major environmental problem of safe disposal of poultry litter (PL). In a comprehensive study, we explored ways of PL use in conservation tillage-based cotton (Gossypium hirsutum L.) production systems on a Decatur silt loam soil in north Alabama, from 1996 to 1999. The study reported here-in presents the residual effects of PL applied to cotton in mulch-till (MT) and no-till (NT) conservation tillage systems in 1997 and 1998 cropping seasons on N uptake, growth, and yield of rye (Secale cereale, L.) cover crop and rotational corn (Zea mays L.) in 1999. Rye was grown without additional N, whereas corn was grown at three inorganic N levels (0, 100, and 200 kg N ha⁻¹). Poultry litter was applied to cotton in 1997 and 1998 at 0, 100, and 200 kg N ha⁻¹. Residual N from PL applied to cotton in 1997 and 1998 produced up to 2.0 and 17.3 Mg ha⁻¹, respectively, of rye cover crop and corn biomass (includes 7.1 Mg ha⁻¹ of corn grain yield) without additional fertilizer. Therefore, in addition to supplying crop residues which reduce soil erosion, increase soil organic matter, and conserve soil moisture, the rye cover crop was able to scavenge residual N left by the cotton crop, which would otherwise, be at risk of being leached and pollute groundwater resources. Poultry litter applied to cotton also increased corn grain quality as shown by up to 100% increase in grain N content compared to the 0N treatment. Using PL with a slower rate of N release compared to inorganic fertilizer to meet some of the N requirements of corn, will not only reduce N fertilizer costs for corn, but will also reduce the risk of nitrate N leaching into groundwater. The maximum amount of crop residues added to the cotton based cropping system by residual N from PL and inorganic N was 21.3 Mg ha⁻¹. This will lead to an increase in soil organic carbon and soil structure in the long term and a reduction in soil erosion, thereby further improving soil productivity, while at the same time, protecting the environment from nitrate pollution and soil degradation. Our study demonstrates that cotton under conservation tillage system in combination with rye cover crop and rotational corn cropping could use large quantities of PL thereby avoiding serious potential environmental hazards.     

Changes in Grain Yield of Rice and Emission of Greenhouse Gases from Paddy Fields after Application of Organic Fertilizers Made from Maize Straw

A field experiment was conducted at the farm of Yangzhou University, Yangzhou, China, to study the effects of organic fertilizers made from maize straw on rice grain yield and the emission of greenhouse gases. Four organic fertilizer treatments were as follows： maize straw （MS）, compost made from maize straw （MC）, methane-generating maize residue （MR）, and black carbon made from maize straw （BC）. These organic fertilizers were applied separately to paddy fields before rice transplanting. No organic fertilizer was applied to the control （CK）. The effects of each organic fertilizer on rice grain yield and emission of greenhouse gases were investigated under two conditions, namely, no nitrogen （N） application （ON） and site-specific N management （SSNM）. Rice grain yields were significantly higher in the MS, MC and MR treatments than those in CK under either ON or SSNM. The MS treatment resulted in the highest grain yield and agronomic N use efficiency. However, no significant difference was observed for these parameters between the BC treatment and CK. The changes in the emissions of methane （CH4） carbon dioxide （CO2）, or nitrous oxide （N20） from the fields were similar among all organic fertilizer treatments during the entire rice growing season. The application of each organic fertilizer significantly increased the emission of each greenhouse gas （except N20 emission in the BC treatment） and global warming potential （GWP）. Emissions of all the greenhouse gases and GWP increased under the same organic fertilizer treatment in the presence of N fertilizer, whereas GWP per unit grain yield decreased. The results indicate that the application of organic fertilizer （MS, MC or MR） could increase grain yield, but also could enhance the emissions of greenhouse gases from paddy fields. High grain yield and environmental efficiency could be achieved by applying SSNM with MR.     

Spatial variability in the growth of direct-seeded rainfed lowland rice (Oryza sativa L.) in northeast Thailand

Large within-field variation in rice growth often causes production loss in broadcast-seeded (BC) rainfed lowland rice. The spatial variability of direct-seeded rainfed lowland rice was evaluated in 2004, 2005, and 2007 in on-station experiments at Ubon Ratchathani, northeast Thailand, in relation to soil water content and weed infestation, by adopting semivariogram and block kriging, including comparisons among BC with harrowing (BCH; no weeding), BC with no harrowing (BCNH; no weeding), and row-seeded (RS; interrow weeding once) fields. BCH and BCNH were also compared in 11 farmers’ fields in 2006 and 2007, to assess the effect of harrowing on rice growth and weed infestation. During most of the rice growing periods, flooded and non-flooded portions existed simultaneously in the fields, with different proportions among years and among seeding methods in the on-station experiment. BCH and BCNH rice had large within-field variation in seedling density, heading date, shoot dry matter, grain yield, harvest index, panicle density, and filled spikelet per panicle, as well as in weed infestation, measured by a quick visual estimation. Many of the measured variables (except mean soil water content in RS in 2007, seedling density in BCH in 2005 and 2007, shoot dry matter in BCH and BCNH in 2007, and panicle density in BCH in 2007) were spatially dependent (i.e., data from nearby locations were most similar) by geostatistical analysis. Analysis of correlations using the 420 data sets of BCH plots in 2005 and BCH, BCNH, and RS plots in 2007 revealed a positive correlation between soil water content and grain yield and negative correlations between weed infestation and soil water content and grain yield. Compared with BCH, in 2007 BCNH had much lower grain yield because of lower soil water content after establishment and more weed infestation. BCH had higher grain yield than BCNH in weedy fields in the farmers’ fields experiment. RS with interrow weeding resulted in a smaller coefficient of variation, smaller sill value, and higher grain yield than BCH, due to less weed infestation and a higher proportion of flooded water. These results indicated that reducing the spatial variability in rice growth requires careful field preparation, such as harrowing to level the soil surface and to reduce the uneven distribution of standing water and the variability in soil water content, combined with effective crop and weed management (i.e., harrowing and row-seeding). This is the first study that examined spatial variability in the growth of direct-seeded rice as a function of soil water content and weed infestation in a rainfed lowland environment.     

Simulating response of maize to previous velvet bean (Mucuna pruriens) crop and nitrogen fertiliser in Malawi

A velvet bean (Mucuna pruriens L.) module for the agricultural production systems simulator (APSIM) was developed in order to assess the nitrogen (N) and yield benefits of velvet bean green manure crops, when grown in rotation with maize in small holder situations in Malawi. The velvet bean module was able to simulate maturity biomass from six contrasting sites in Malawi over an observed range of 847–10,420 kg/ha with a root mean squared deviation (RMSD) of 1562 kg/ha. APSIM was then tested for its ability to simulate the response of maize crops to fertiliser N in two seasons, to previous velvet bean green manure crops in one season, or both in combination in one season. With no previous velvet bean crop, the response to fertiliser N varied across sites from a non-significant increase to an eight-fold increase in maize yield. Where a velvet bean crop was grown in the previous season, the response to applied N varied from non-significant to slight. Simulated yields were within one standard error of the observed in the majority of cases. A sensitivity analysis for key parameters in the velvet bean module highlighted, that those governing the N content of crop root and shoot residues had greatest impact on maize yield response. Parameters controlling production and partitioning of root or shoot biomass were less important.To our knowledge this is the first reported case of a cropping systems simulation model being tested for its ability to simulate the production of a green manure legume followed by a cereal.     

Effects of nitrogen,phosphorus and vermicompost on groundnut yield in Babile District,eastern Ethiopia

Groundnut is a major cash crop for smallholder farmers in several districts of eastern Ethiopia with low yield. Little or no fertilizer was applied for the crop possibly because no generic or recommended fertilizer and technology were available. Therefore, field experiments were conducted for 2 consecutive cropping seasons in Babile District, to investigate effects of applying mineral N and P fertilizer and vermicompost (VC) on seed yield and oil content of groundnut using an improved variety ‘BaHa-Gudo’. Treatments consisted of nitrogen (0,23 and 46 kg N/ha), phosphorus (0,46 and 92 kg P2O5/ha) and VC (0,2.5 and 5 t VC/ha). Results revealed that yield attributes, seed yield and seed oil content were significantly (p < 0.01) affected by fertilizers. Seed yield after combined application of 46 kg N, 46 kg P2O5 and 2.5 t VC/ha increased by about 113% compared to seed yield without any fertilizers. Enhancement in seed oil content at the aforementioned rate was 7.0%. It could, thus, be concluded that applying the aforementioned fertilizers would enable farmers to increase seed yield and oil content of groundnut for enhancing their income and livelihoods in the study area.     

Simulating grain yield and plant development of ratoon grain sorghum over diverse environments

Crop simulation may provide an inexpensive means to evaluate the feasibility of different cropping practices to optimize productivity and profitability. One practice, ratoon-cropping, may increase productivity and reduce per-unit production costs associated with conservation tillage farming systems in tropical and subtropical regions. sorkam, a dynamic plant growth model for grain sorghum [Sorghum bicolor (L.) Moench], was used to evaluate the potential of rainfed ratoon grain sorghum over diverse climatic regions of Texas. Eleven independent data sets collected in the U.S.A. from sites in Georgia and Texas were used to determine the model's accuracy. The model produced realistic estimates of grain yield for planted, ratoon, and combined (planted + ratoon) crops. Simulated grain yields usually were within 25% of the observed yield for the planted, ratoon, and combined crops with cultivars that produced the highest ratoon grain yield at each location. Ratoon grain yield results of multi-year simulations (10–30 years) from 14 locations over the eastern half of Texas using historic, location-specific, meteorological data indicated that the probability of obtaining ratoon grain yield > 3.0 Mg/ha was confined to the upper coastal plain region of Texas. The area best suited for rainfed ratoon grain sorghum appeared to be confined south and east of a line running from west of Corpus Christi to Beeville to College Station to west of Center, Texas. Use of crop models can play an important role in identifying strengths and weaknesses of potential cropping systems when used in combination with historical climatic data and/or computer weather generators.     

Evaluation of management principles and performance of the System of Rice Intensification (SRI) in Bangladesh

Experiments were conducted at irrigated and rainfed lowland rice sites in Bangladesh to assess the performance of management practices that have become known as the System of Rice Intensification (SRI). At a research station, SRI management principles such as seedling age, plant spacing, application of organic manure, seedling densities, duration of planting, planting shape and time of planting were evaluated under SRI management as compared to previously established Best Management Practices (BMPs). In on-farm trials, SRI was compared with BMP on 40 farmers’ fields. Nutrient inputs and water management in BMP and SRI treatments were kept at comparable levels. Seedling age, ranging from just sprouted seed to 40-day-old seedlings, had no effect on grain yield in the winter season. In a plant spacing experiment subject to SRI, the highest and lowest grain yields of 7.82 and 5.41 t ha⁻¹ were obtained with spacing of 25 cm × 15 cm (narrow) and 40 cm × 40 cm (wide), respectively. In SRI, seedling density (1–2 seedlings per hill), planting durations (≤15 min to 1–3 h after uprooting) or root placement (L-shape and J-shape) had no effect on grain yield. With regard to time of planting, the highest grain yields were observed with transplanting in the 3rd week of December, with no difference between SRI and BMP management systems. In on-farm trials, BMP gave significantly higher grain yield compared to SRI and farmers’ practice in a triple-cropped area, but grain yields were similar with SRI in a double and single-cropped area when spacing was narrow. The highest profit was obtained with BMP followed by SRI and farmers’ practice in the single-cropping area. Major findings from this study are that under comparable levels of net nutrient input and water management (i) well-implemented BMPs for rice are more efficient for producing high yields than SRI and (ii) there is no intrinsic yield advantage of SRI that could be caused by its individual crop management techniques or some unknown synergism of the different SRI practices proposed.     

Yield of rice under water and soil salinity risks in farmers’ fields in northeast Thailand

This study focused on the variability of rice yield under water and soil salinity risks in farmers’ fields in northeast Thailand. A rice plot was monitored in 24, 16 and 11 farmers’ fields during the rice seasons 2005, 2006 and 2007, respectively. The results emphasized that few plots were continuously submerged during the 2005 season, when rainfall was low. Drought significantly affected the rice yield, yield components and the internal efficiency (IE) of the absorbed nutrients, while slight soil salinity had the only significant effect of increasing the IE of potassium (IEK). In the very rainy 2006 and 2007 seasons, most fields were continuously submerged, and in contrast to 2005, the slight soil salinity that was recorded had significant effects not only on IEK, but also on rice yield, spikelet sterility and 1000-grain weight. The yield decrease due to drought was about 87% and that due to salinity was 20%. When neither salinity nor water were limiting, the soil nutrient supply was high enough to achieve about 80% of the maximum yield reported in the literature for the rice cultivar in this area. As both drought and salinity risks are hardly avoided by the current farmers’ management they should be taken into account in the way technical recommendations to farmers are formulated.     

On-farm evaluation of the ‘push–pull’ technology for the control of stemborers and striga weed on maize in western Kenya

The ‘push–pull’ technology is a novel pest management strategy developed for control of stemborers and striga weed, Striga hermonthica, in maize-based farming systems in eastern Africa, where maize is intercropped with desmodium, a forage legume, and Napier grass is planted as a border crop. Desmodium repels stemborer moths while Napier grass attracts them. Desmodium also suppresses the parasitic striga weed through a series of mechanisms ranging from shading to allelopathy through the root system. The technology is currently being disseminated among smallholder farmers in eastern Africa and adoption rates are rising. Our on-station studies have reported efficacy of this technology against the two pests resulting in increased grain yields. The current study was conducted between 2003 and 2006 in 14 districts in western Kenya to assess effectiveness of the technology under farmers’ own conditions. Twenty farmers from each district, who had adopted the technology, were randomly selected for the study. Each farmer had a set of two plots, a ‘push–pull’ and a maize monocrop. Seasonal data were collected on percentage of maize plants damaged by stemborers, the number of emerged striga, plant height and grain yields. Similarly, farmers’ perceptions on the benefits of the technology were assessed using a structured questionnaire. Stemborer damage and striga counts to maize plants were significantly lower in the ‘push–pull’ plots than in the maize monocrop plots. Similarly, maize plant height and grain yields were significantly higher in the former. Farmers rated the ‘push–pull’ technology significantly superior in having reduced stemborers and striga infestation rates and increased soil fertility and grain yields. These results demonstrate that the technology is equally effective in controlling both pests with concomitant yield increases under farmers’ conditions in the districts studied.     

定位施肥对甘蔗产量及土壤肥力的影响

根据1998～2003年连续6年在福建省仙游县大济镇坑北村进行甘蔗连年保持不变的定位施肥研究,结果表明:有机无机肥结合使用和化肥合理配施与当地群众习惯施肥比较,其增产增收效果显著。同时,有机无机肥结合使用具有增强土壤自身能力,是培肥地力的一条有效途径;化肥合理配施对培肥土壤也有一定的促进作用,在农业生产上,是不可忽视的一项先进施肥技术措施。试验结果还表明:长期不施肥会造成土壤衰竭,地力贡献率急剧下降,必须合理补充肥料以归还作物所带走的养分,尤其要投入足量的有机肥料,使其土壤有机质维持在一定水平上,以保持土壤养分平衡。     

Grain Yield of Sorghum Cultivars in a Double Cropping System

Abstract

Field experiments were conducted at the experimental field of Kyushu University, northern Kyushu in 1996 and 1997 to investigate the possibility of a double cropping of sorghum using early maturity cultivars. The effects of sowing date (early or late) and the cultivar on the yield were also examined. On the average, grain yield from double cropping was 556 g m^?2 in 1996 and 746 g m^?2 in 1997. Sowing date greatly influenced the major traits of the summer crop, but not significantly those in the spring crop, except for the days to heading. Late summer sowing decreased grain yield as much as 41.9%, decreased 100-grain weight by 22.4% and extended days to heading. Early sowing, early in April and late in July or early in August, is recommended for spring and summer crops, respectively, in a double cropping system to obtain a high grain yield. SA 403, D12, C8, C9, D5 C10-1 F₄ line and D5 × C8 (F₁ hybrid) were considered to be suitable for a double cropping system.     

稻田年内水旱轮作的后效应研究

 在麦-稻-稻和麦-玉米-稻两种种植方式6年定位试验的基础上,对稻田年内水旱轮作的后效应进行了研究。结果表明：年内水旱轮作能显著地提高后作晚稻和大麦产量,但后效持续时间不长,到第三季后作物早稻增产已不明显。生产上两种种植方式以隔年轮换为好。增产的主要原因是年内水旱轮作改善土壤通透性,能增加土壤有效氮、磷、钾含量和提高根系活力,促进了作物生长和养分吸收,从而增加晚稻有效穗、结实率和实粒数,增加大麦有效穗和千粒重。试验也表明,增施肥料会降低轮作效果。