品种搭配对湖北省玉米-晚稻复种产量及资源效率的影响

Maize-late rice cropping (M-R) is considered to coordinate the production of food and feed crop. In recent years, M-R has begun to develop in the middle reaches of the Yangtze River. However, technologies have not been systematically studied and improved for its higher yield and higher resources use efficiency. Especially, a reasonable collocation of varieties between maize and late rice seasons is an important basis to realize the yield potential of M-R, and still is under evaluation. In this study, different maize and late rice varieties were selected and collocated to different M-R modes. Their yield performance and use efficiency of resources were detected in different regions of Hubei province in 2015 and 2017. The results showed that under different heat conditions, the varieties collocation modes had significant effects on the annual yield of M-R and the production efficiency of resources. The modes of medium maturity maize-late indica rice cropping had obviously higher annual yield and resource production efficiency under higher accumulated temperature (GDD_≥10°C); on the contrary, the annual yield and resource production efficiency of the modes of early maturity maize-late indica rice cropping were higher under lower GDD_≥10°C. The utilization percentage of the annual effective GDD_≥10°C of each varieties combination mode could reach 95.6%-100.0%, and the distribution ratio of GDD_≥10°c between previous and subsequent season (TR) had a significant non-linear relationship with the relative annual yield of M-R. When the utilization percentage of GDD_≥10°C was 97.0%-98.5% and TR was 1.06-1.08, M-R could obtain highest annual yield. Therefore, suitable varieties of maize and late rice could be selected according to the local heat resource and reasonable TR. In summary, high-yield maize varieties with a growth period of 125 days and late rice varieties with a growth period of 140 days should be selected for the southern regions with higher GDD_≥10°C, while high-yield maize varieties with a growth period of 120 days and late rice varieties with a growth period of 130 days should be selected for the middle and northern regions with relatively lower GDD_≥10°C in Hubei province.     

Straw management, crop rotation, and nitrogen source effect on wheat grain yield and nitrogen use efficiency

Nitrogen fertilizer management from different sources and annual crop rotations are important components of wheat (Triticum aestivum L.) production systems, especially where air and soil quality issues have prompted a search for alternatives to wheat straw burning. This study examined the effects of two different wheat straw management options (burning and incorporation by tillage), three crop rotations [wheat-sesbania (Sesbania spp.), wheat–maize (Zea mays L.), and wheat-clean fallow] and three N sources (urea, chicken manure, and urea plus chicken manure) on wheat grain yield and N use efficiency. The experiment was conducted as split–split plot treatment arrangement with three replications for eight wheat cropping seasons in the state of Sonora, Mexico. Results indicated that both wheat grain yield and N use efficiency were higher with burning than incorporation of wheat straw and with fertilization with urea or urea plus chicken manure than chicken manure alone. As shown by the crop rotation-by-straw management interaction, planting sesbania following incorporation of the straw by tillage produced comparable grain yields to straw burning treatment. In contrast, wheat in annual rotation with maize produced the lowest wheat grain yield and N use efficiency irrespective of the wheat straw management and N source applied.     

Effects of tillage,crop systems and fertilization on weed abundance and diversity in 4-year dry land winter wheat

The arable fields in central Spain have been dominated by cereal production, especially winter wheat. In this area, the defined action of weed management program requires a clear understanding of the factors and mechanisms conditioning weed community dynamics in agro systems. This study evaluated the effects of different agricultural management systems on the abundance and diversity of weed communities in winter wheat crops.Weed density and composition of weed species were sampled over four years; comparing monoculture wheat and rotational wheat in three agricultural management systems: (1) direct drilling (no-tillage, NT); (2) chisel ploughing (minimum tillage 15 cm depth, MT) and (3) mouldboard ploughing (traditional tillage 20 cm depth, CT). With the aim to be able to improve weed management in agro systems with semiarid environments; within each of the agricultural management systems, we examined the impact of mineral fertilization (traditional and balanced) as a tool for reducing the external inputs in arable cereals.Weed diversity was assessed using the three common diversity indices: Shannon's index, evenness index and species richness. The data collected showed total weed density was different per tillage system and each year of the study, but we did not find significant differences between crop systems over the study.The abundance, diversity and evenness of the weed community in the arable field, were significantly increased in NT systems. Within the direct drilling (NT) plots, rotational wheat showed the highest levels of weed infestation and diversity. Comparing traditional and balanced mineral fertilization of soil did not reveal a significant effect on weed abundance and diversity observed in field.     

水肥“三匀”技术对水稻水、氮利用效率的影响

This study included three split-plot designed experiments. Experiments 1 and 2 were conducted in two fields with varied soil fertility and consistent treatment. Two rice varieties (Dexiang 4103, high NUE; Yixiang 3724, low NUE) were set as main plot. The sub-plot contained six nitrogen-water management modes (farmer’s usual management, FU; nitrogen-water coupling management, NWC; methodical nitrogen-water distribution management, MNWD; and their respective nitrogen-free controls). The main plot of Exp.3 was two high NUE varieties (Dexiang 4103, Fyou 498) and two low NUE varieties (Yixiang 3724, Chuanyou 6203); FU, NWC, and MNWD assembled the sub-plot. MNWD adopted the method of increasing frequency and reducing quantity, thus the nitrogen application rate was reduced by 20% compared with NWC and FU, the irrigation water amount was reduced by 20% to 25% compared with NWC, and 42% to 48% compared with FU. The stem number of MNWD changed smoothly and its ear bearing tiller percentage was higher. Compared with NWC and FU, the photo assimilation before anthesis MNWD had less, dry matter transportation before anthesis and high accumulation of assimilate after anthesis. The grain yield of MNWD was similar to that of NWC, while 8.77%-14.18% higher than that of FU. Correlation analysis showed that the dry weight of roots in 10-20 cm and 20-30 cm soil layers were significantly and positively correlated with nitrogen recovery efficiency (NRE), nitrogen agronomy efficiency (NAE), irrigation water production efficiency (IWPE) and water production efficiency (WPE). MNWD had a large amount of root system distributed in the soil layer below 10 cm, which was conducive to the improvement of water and nitrogen utilization efficiency. Compared with NWC and FU, MNWD increased NRE by 8.07%-11.99% and 20.72%-30.78%, NAE by 17.44%-27.38% and 96.47%-101.42%, IWPE by 23.34%-36.67% and 76.54%-117.38%, WPE by 8.41%-17.66% and 32.23%-65.29%, respectively.     

作物不同品种间水分利用效率差异机理的研究进展

近年来,水分不足是限制我国北方干旱和半干旱区粮食生产的重要因子。生物节水是实现进一步提高作物水分利用效率的关键环节和潜力所在。笔者就作物水分利用效率的内涵和不同品种间水分利用效率差异的生理生态机理进行了综述,并提出了水分利用效率的研究方向。目前应进一步深入研究作物高效用水生理调控机理和抗旱节水鉴定评价技术与指标体系,为培育高WUE品种提供理论基础。     

Optimisation of fertiliser rates in crop production against energy use indicators

Optimising mineral nitrogen (N) use in crop production is inevitable target as mineral fertilisers reflect one of the highest inputs both in terms of economy and energy. The aim of the study was to compare the relationship between the rate of N fertiliser application and different measures of energy parameters exemplary data for spring-wheat in boreal climate condition in Estonia in 2006–2010. The effect of mineral N with rates 0, 40, 80, 120 and 160 kg N ha⁻¹ was studied on the background of composted cow manure and without organic fertilisers. Univalent parameters, energy gain (EG) (energy output − energy input) and energy ratio (ER) (energy output/energy input) were calculated. To aggregate parameters with different units (ER and EG) we proposed two standardisation approaches for combined indices. ER maximisation gave both organic fertilisation background optimum N norms significantly lower than EG (p < 0.05) optimisation. Both the new combined indices gave optimum N norms in between the rate of ER an EG. Composted cow manure background did not affect mineral N optimisation significantly. We suggest optimisation of mineral N according to bi-dimensional parameters as they capture important features of production efficiency and are more objective using as advisory tool for sustainable production systems.     

Phosphorus management in low input stockless cropping systems: Crop and soil responses to contrasting P regimes in a 36-year experiment in southern France

Fertiliser recommendation systems should aim at a finer tuning of non-renewable P inputs for agronomic, environmental and economic reasons. Modern decision support systems should take into account the relevant soil characteristics, the P recycling capabilities of the cropping system, and crop requirements for attainable production in a range of soil/weather conditions. Unfortunately, information is still lacking for low input cropping systems in south-western France. In 1968 INRA Toulouse set up a P experiment, which has been going on for 36 years, on a deep alluvial silty-clay/clay soil with varying CaCO₃. Four P regimes (P0, P1, P2, P4) were arranged in four blocks with periodic changes in the fertiliser dressings. Wheat, maize, sunflower, sorghum and soybean were tested for grain yield (GY) and grain P concentration (GPC) response to soil Olsen P concentration. The highest GY were observed in both P2 and P4, although P1 yields were significantly lower in only 4 years out of 36. P0 resulted 32 times in lower yields than P2–P4 and 27 times in lower yields than P1. Wheat was the crop most sensitive to the absence of P fertilization (GY_P0/GY_Pmax = 0.72); maize and sorghum were intermediate (0.77) and sunflower was the less sensitive on average (0.83). As the highest GPC values were observed in the P4 treatments, P removal was maximum for P4 (21.9 kg P ha⁻¹ year⁻¹) and minimal in P0 (11.7 kg P ha⁻¹ year⁻¹). The critical soil Olsen P values for yield responses were determined using the Cate–Nelson and Mitscherlich approaches. Although the thresholds differ for the two methods (3.3–7.2 mg P kg⁻¹ with Cate–Nelson; 4.4–11.2 mg P kg⁻¹ with Mitscherlich), crops ranked similarly with both methods. Critical soil P values were lowest for maize and highest for sunflower, while wheat, soybean and sorghum had intermediate values. Because of low-input management and frequent water stress, critical values fall within the lower range of published values. Only in the P4 treatment were P-Olsen values potentially hazardous for the environment (>20 mg P kg⁻¹) 8–10 years after the beginning of the experiment. Annual P dressings of 17.5 kg P ha⁻¹ year⁻¹ (P1) were sufficient to achieve good yields but P dressings of 35 kg P ha⁻¹ year⁻¹ (P2) were necessary to stabilize soil P around the critical level in the calcareous part of the experiment.     

Designing cropping systems for efficient use of limited water in southern Australia

There has been continuous change in the systems of cereal production in southern Australia where the climate is semi-arid with moderately wet winters and hot dry summers. At the outset wheat (c. 1840) was grown in continuous culture as the land was gradually cleared for cropping, but yields declined to uneconomic levels by 1900. That system was then replaced with fallow-wheat rotations, and using phosphorus fertilizer, yields recovered, but not to the original level. From 1945, the high profitability of sheep production encouraged improvement of legume-based pastures and the introduction of pasture-crop sequences – ley-farming. Productivity was greatly increased and the yield of wheat crops regained the original level. But such were the rates of acidification and salinization of soil that reduced productivity and, in the case of salinity, reduced stream quality and threatened adjacent natural ecosystems. This ley-farming system was used until the late 1980s when prices for wool fell dramatically, and farmers reduced sheep numbers and intensified cropping. The thrust since then has been to design cropping systems that are economically as well as environmentally acceptable with salinity control as the major objective. There is now a search for systems that use more water to reduce drainage through the soil and lower saline water tables. A major contribution is the much restricted use of fallow but summer active plants are also required to provide a soil water storage buffer to retain autumn–winter rainfall. New systems under evaluation include herbaceous perennials such as lucerne that are readily integrated into a crop-livestock system and agroforestry combinations with various trees. The design and appropriate distribution of the new systems is aided by remote sensing techniques to locate areas of saline discharge and linkages to zones of groundwater recharge, geographical information systems to arrange the data for land system analysis, and computer models of crops and cropping systems. There is a substantial challenge for farmers, agronomists and others to identify and assess suitable new systems and to bring the public into the debate and into the solution.     

长期施肥对红壤旱地作物产量及肥料效益影响

摘要：通过对红壤旱地13年连续监测研究,发现在红壤地区红壤旱地上：长期使用化学肥料,其肥料利用率和作物产量表现为逐步下降的趋势。在N处理中,前5年比CK处理,玉米平均增产213%,小麦增产96%;10年以后,玉米平均减产45%,小麦减产85%;在NP、NK、NPK处理中,与N处理具有相同的趋势;在NPKM、M处理中,玉米和小麦产量表现为平稳和轻微的上升趋势。肥料的利用率变化与产量变化具有同一性。为提高红壤旱地玉米和小麦子粒的品质,使用化学氮肥是一项必不可少的技术措施,同时化学氮肥对玉米和小麦子粒品质提高效果大于有机氮。     

Low-input cropping systems to reduce input dependency and environmental impacts in maize production: A multi-criteria assessment

Intensification of cropping systems in recent decades has increased their productivity but affected air, soil and water quality. These harmful environmental impacts are exacerbated in Maize Monoculture (MM) and hasten the need for solutions to overcome the trade off between crop yield and environmental impacts. In a three-year cropping systems experiment, a conventional intensive maize monoculture (MM_Conv), with a winter bare fallow, deep soil tillage, non-limiting irrigation was compared to three Low Input Cropping Systems (LI-CS) designed as alternatives to the conventional system. They were managed with decision-rules implemented to reach specific objectives of input reduction. The LI-CS designed with Integrated Weed Management (IWM) techniques and other sustainable cropping practices, were:(i) MM_LI—an IWM Low Input MM; (ii) MM_CT—a Conservation Tillage combined with cover crop MM; and (iii) Maize-MSW—an IWM maize grown in rotation with soybean and wheat. A comprehensive multi-criteria assessment was carried out to quantify the agronomic, economic, social, and environmental performances of each system. A canonical discriminant analysis of performance metrics revealed large differences between the four systems. Yields were significantly higher in MM_Conv (11.0 Mg ha⁻¹) and MM_LI (10.3 Mg ha⁻¹) than in Maize-MSW (8.6 Mg ha⁻¹) and MM_CT (7.8 Mg ha⁻¹). MM_CT had the largest weed infestation (density and biomass) despite the greatest use of herbicides. The Herbicide Treatment Frequency Index (HTFI), used to indicate differences in herbicide use, revealed that the MM_LI (HTFI = 1.0) and Maize-MSW (1.1) halved the herbicide use as compared to the MM_Conv (2.1), despite having similar weed abundance levels. The LI-CS, especially MM_CT, produced high biomass winter cover crops and then less nitrogen fertilization was required as compared to MM_Conv. Gross margins in the MM_LI (1254 € ha⁻¹) and MM_Conv (1252 € ha⁻¹) were higher than the MM_CT (637 € ha⁻¹) and Maize-MSW (928 € ha⁻¹). MM_LI and MM_Conv had similar labour requirements. Water drainage, pesticide leaching, energy use, and estimated greenhouse gas emissions were higher in MM_Conv than in the LI-CS in most years. Results from this research show good potential for the MM_LI to reduce the environmental impacts of MM_Conv while maintaining its economic and social performance.     

Italian ryegrass establishment by self-seeding in integrated crop-livestock systems: Effects of grazing management and crop rotation strategies

We evaluated the re-establishment of an Italian ryegrass pasture by self-seeding on a no-till integrated crop-livestock systems (ICLS) in the southern region of Brazil. This work is part of a long-term experimental protocol initiated in 2003. We tested the effects of various management practices, such as summer crop systems (soybean vs. maize–soybean rotation), stocking methods (continuous vs. rotational) and grazing intensities (low vs. moderate), on Italian ryegrass pasture establishment. In addition, we tested resilience of the system by testing pasture's ability to re-establish following a year without seed head production. The experiment consisted in the rotation, on the same area, of Italian ryegrass pasture grazed by sheep during the winter and up to the end of the grass production cycle, and soybean or soybean-maize grain crops rotation cultivated during the summer. The pasture established itself by self-seeding since 2005. Data were collected in 2011 and 2012 stocking season. The soybean summer crop, continuous stocking and low grazing intensity, all positively affected the production of reproductive tillers in 2011. Grazing intensity in 2011 strongly influenced early vegetative tiller densities (before crop harvest) in 2012. However, none of the grazing intensity or the stocking method treatments affected herbage mass at the end of pasture establishment in 2011 or 2012. On the other hand, the soybean summer crop positively affected pasture establishment, both in term of tiller densities and herbage mass at the end of pasture establishment. The removal of all seed heads in 2011 (preventing seed production) resulted in the total failure of pasture establishment in 2012. Overall, Italian ryegrass establishment by self-seeding relies on the annual replacement of the soil seed bank. This experiment demonstrated that under various stocking methods, moderate grazing intensity and maize or soybean summer crop, Italian ryegrass pasture establishment by self-seeding remains successful even when the stocking periods extended up to the end of the grass production cycle. Self-seeding with moderate grazing intensity ensures successful pasture establishment, reduces labour and costs and allows to increase the stocking period and so animal live weight gain over the grazing season.     

Legume genetic resources: management, diversity assessment, and utilization in crop improvement

Grain legumes contribute significantly to total world food production. Legumes are the primary source of dietary proteins in many developing countries, where protein hunger and malnutrition are widespread. Grain legumes germplasm constitute ~15% of the 7.4 M accessions preserved globally. Nearly, 78% of the CGIAR??s, 0.217 M accessions, have been characterized, compared to 34% of national genebank collections. Interestingly, limited data on grain quality are available as the primary focus has been on morpho-agronomic traits. Clearly, more resources should be targeted on biochemical evaluation to identify nutritionally rich and genetically diverse germplasm. The formation of core and mini core collections has provided crop breeders with a systematic yet manageable entry point into global germplasm resources. These subsets have been reported for most legumes and have proved useful in identifying new sources of variation. They may however not eliminate the need to evaluate entire collections, particularly for very rare traits. Molecular characterization and association mapping will further aid to insights into the structure of legume diversity and facilitate greater use of collections. The use of high resolution elevational climate models has greatly improved our capacity to characterize plant habitats and species?? adaptive responses to stresses. Evidence suggests that there has been increased use of wild relatives as well as new resources resulting from mutagenesis to enhance the genetic base of legume cultigens.     

Genetic diversity and path analysis for nitrogen use efficiency in popcorn inbred lines

Popcorn inbred lines with more efficient nitrogen use are better able to uptake nitrogen from the soil and convert it into higher grain yield, resulting in lower environmental and economic impacts caused by nitrogen fertilization. The objectives of this study were to (i) identify inbred lines superior in nitrogen use (ii) assess the genetic diversity between popcorn inbred lines under high and low N conditions and (iii) investigate the causal effects of several traits in nitrogen use efficiency (NUE). We evaluated 25 popcorn inbred lines under high and low N, and several traits related to NUE and its components were measured. Efficient and inefficient inbred lines under both N levels were identified and can be useful for generating a segregating population for quantitative trait loci mapping. The genetic diversity assessment based on phenotypic traits grouped the inbred lines into four clusters under both N levels, and the efficient inbred lines were grouped together, as were the inefficient lines. The most divergent inbred lines under high N were classified as efficient and intermediate and can be useful to generate a divergent breeding population with a high frequency of favorable genes for NUE. Nitrogen uptake efficiency (NUpE) was considered the most important trait for NUE. To improve the accuracy of selection for NUE, a selection index involving the total root length (TRL), daily growth and NUpE traits under both N levels is recommended, as these traits had high correlations with and direct effects on NUE.     

Global warming likely reduces crop yield and water availability of the dryland cropping systems in the U.S. Central Great Plains

We investigated the impact of GCM-projected climate change on dryland crop rotations of wheat-fallow and wheat-corn-fallow in the Central Great Plains (Akron in Colorado, USA) using the CERES 4.0 crop modules in RZWQM2. The climate change scenarios for CO₂, temperature, and precipitation were produced by 22 GCM projections for Colorado based on the A1B scenario. The climate change for years 2050 and 2075 was super-imposed on measured 30-year-baseline climate data (1989–2008). For all the cropping rotations and projection years, simulated yields of wheat and corn decreased significantly (P < 0.05) with increasing temperatures. The yield declines due to the elevated temperatures should be attributable to the shortening of crop maturity duration and concurrent decreases in soil water and evapotranspiration. The model was also projected to decrease crop yields for the combined climate change scenarios of CO₂, temperature, and precipitation in the dryland cropping rotations.     

Effects of biogas digestion of clover/grass-leys, cover crops and crop residues on nitrogen cycle and crop yield in organic stockless farming systems

The trend towards specialization in conventional farming led to large agricultural areas in Germany and in Europe lacking livestock. Also stockless organic farming has increased during recent years. In organic farming clover/grass-ley (CG) provides nitrogen (N) to the whole cropping system via symbiotic N₂ fixation and also controls certain weeds. A common practice in organic farming, when ruminants are not present, is to leave the biomass from CG in the field for their residual fertility effect. CG biomass, crop residues (CR) and cover crops (CC) represent a large unexploited energy potential. It could be used by anaerobic digestion to produce biogas. A field experiment was carried out by implementing a whole cropping system with a typical crop rotation for such farming systems on the research station Gladbacherhof from 2002 to 2005. The crop rotation consisted of six crops (two legumes and four non-legume crops). The aim was to evaluate whether the use of N could be improved by processing biomass from CG, CR and CC in a biogas digester and using the effluents as a fertilizer, compared to common practice. In the control treatment, represented by the usual stockless system, the CG, CR and CC biomass were left on the ground for green manure purposes. In the biogas systems these substrates were harvested for digestion in a biogas plant. The effluents of digestion were used to manure the non-legumes in the same crop rotation. Results indicate that digestion of CG, CR and CC can increase the crop dry matter and N yields and the N content of wheat grains in organic stockless systems. Harvesting and digestion of residues and their reallocation after digestion resulted in a better and more even allocation of N within the whole crop rotation, in a higher N input via N₂ fixation and lower N losses due to emissions and probably in a higher N availability of digested manures in comparison to the same amounts of undigested biomass.     

Use of soil and vegetation spectroradiometry to investigate crop water use efficiency of a drip irrigated tomato

An agronomic research was conducted in Tuscany (Central Italy) to evaluate the effects of an advanced irrigation system on the water use efficiency (WUE) of a tomato crop and to investigate the ability of soil and vegetation spectroradiometry to detect and map WUE. Irrigation was applied following an innovative approach based on CropSense system. Soil water content was monitored at four soil depths (10, 20, 30 and 50 cm) by a probe. Rainfall during the crop cycle reached 162 mm and irrigation water applied with a drip system amounted to 207 mm, distributed with 16 irrigation events. Tomato yield varied from 7.10 to 14.4 kg m⁻², with a WUE ranging from 19.1 to 38.9 kg m⁻³. The irrigation system allowed a high yield levels and a low depth of water applied, as compared to seasonal ET crop estimated with Hargraves’ formula and with the literature data on irrigated tomato. Measurements were carried out on geo-referenced points to gather information on crop (crop yield, eighteen Vegetation indices, leaf area index) and on soil (spectroradiometric and traditional analysis). Eight VIs, out of nineteen ones analyzed, showed a significant relationship with georeferenced yield data; PVI maps seemed able to return the best response, before harvesting, to improve the knowledge of the area of cultivation and irrigation system. CropSense irrigation system reduced seasonal irrigation volumes. Some vegetation indexes were significantly correlated to tomato yield and well identify, a posteriori, crop area with low WUE; spectroradiometry can be a valuable tool to improve irrigated tomato field management.     

早晚兼用型优质稻泰优398双季连作高效种植模式

泰优398是广东省农业科学院水稻研究所和江西现代种业股份有限公司共同选育的早熟、优质、早晚兼用型三系杂交水稻品种(审定编号:赣审稻2012008、赣审稻20190017)。为了探究泰优398早晚连作模式的优越性,于2018年在江西省安排了7个生态点的种植试验。结果表明,在稻谷价格低迷的大环境下,泰优398早晚连作种植模式可为种植户带来高效益,是农业提质增效、农民增产增收的新途径。     

Integrating farmer knowledge,precision agriculture tools,and crop simulation modelling to evaluate management options for poor-performing patches in cropping fields

Cropping fields often have poor-performing patches. In an attempt to increase production on poor patches, farmers may apply additional fertiliser or ameliorants without economic or scientific justification. Improved understanding of the extent and causes of poor performance, management options, potential crop yield and economic benefits can give farmers the tools to consider management change. This paper presents an approach to integrating farmer knowledge, precision agriculture tools and crop simulation modelling to evaluate management options for poor-performing patches.We surveyed nine cropping fields in Western Australia and showed that (1) farmers have good understanding of the spatial extent and rank performance of poor-performing areas, when compared to NDVI or yield maps, (2) there is a wide range of physical and chemical soil constraints to crop yield in such patches, some of which can be ameliorated to raise yield potential, and others where crop inputs such as fertiliser can be better matched to low yield potential.Management options for poor-performing patches were evaluated through simulation analysis by removal of constraints to rooting to varying extents, and hence plant available water capacity. These examples show that if the constraint is mis-diagnosed then the potential benefits from amelioration can be overstated. In many cases constraints, often associated with physical limitations such as shallow available rooting depth or light-texture cannot be ameliorated or are uneconomic to ameliorate. In such cases the best intervention may be to lower crop inputs to better match the water-limited yield potential of such poor-performing areas.This research integrated farmer knowledge and spatial data to define yield zones in which targeted soil sampling and crop simulation were then used to determine yield potential and particular constraints to that potential. The economic costs and benefits of differential zone management were examined under a range of husbandry scenarios and, importantly, the sensitivity of economic gain to mis-diagnosis or errors in defining the zones was tested. This approach provided farmers with a robust and credible method for making decisions about spatial management of their fields.     

水稻蚕豆轮作条件下长期定位施肥制度对作物产量的影响

为了解水稻蚕豆轮作条件下,不同施肥制度对作物产量的影响,在云南省通海县碧溪村通过15年的定位施肥田间小区试验,研究了4种施肥制度对水稻和蚕豆的增产效应和稳产性能。结果表明：不同施肥制度对作物产量有明显的影响,水稻平均产量OM＋NPK〉NPK〉OM〉CK,蚕豆平均产量OM＋NPK〉OM〉NPK〉CK;农家肥和化肥配施（OM＋NPK）、氮磷钾配施（NPK）和只施用农家肥（OM）3种施肥结构对水稻产量的贡献率分别为35.37%,33.12%和30.76%,对蚕豆产量的贡献率分别为42.79%,38.14%和39.47%;农家肥化肥配施有利于水稻蚕豆轮作体系作物高产、稳产,农家肥完全替代化肥时水稻产量有一定的减少,但后茬蚕豆产量有所提高;从蚕豆实际产量分析,只在前茬水稻进行施肥不能满足后茬蚕豆正常生长发育的需要,要实现蚕豆高产、稳产需要适当施用磷、钾肥及微量元素。