Nitrogen Use at the Leaf and Canopy Level

Summary

This chapter reviews how N affects biomass production in a canopy by looking at its effects on radiation interception and radiation use efficiency, and the main processes behind them, i.e., leaf expansion, senescence and photosynthesis. Examples have been mostly drawn from extensive grain crops, but most of them extend to pastures or horticultural crops. Understanding the magnitude and dynamics of N demand and availability during critical periods for yield definition was identified as crucial to improve the efficiency of N use at the crop canopy level. Genetic variability in processes that could influence N use efficiency, and the complexity involved in scaling from cellular to crop level are discussed.     

Ecological Context for Examining the Effects of Transgenic Crops in Production Systems

SUMMARY

Ecological processes can have strong effects on production systems, many of which prevent crops from reaching their maximal yield. Past and present management strategies have been developed to mitigate the negative interactions, thereby improving crop production. However, when applied to complex and variable agroecosystems, some of these strategies have resulted in unintended ecological effects that ultimately hindered production. Transgenic crops are a widespread and powerful management option, and there is a tremendous need to understand their intended ecological effects as well as potential unintended direct and indirect effects. The purpose of this review is threefold: (1) to discuss four of the major ecological effects that limit crop production: competition, herbivory, disease, and abiotic stresses, (2) to describe how biotechnology is addressing these problems, and (3) to examine the ways these biotechnological solutions may cause ecological effects that unintentionally hinder crop production. We find that, to date, there has been little diversity in the types of transgenic crops available and the approaches they use to improve crop production. Transgenic crops, like previous agricultural technologies, are designed to enhance a singular plant trait in order to solve a specific production problem. When viewed in a simplified system, transgenic crops seem to provide effective means to mitigate negative ecological effects. However, when approached via a larger ecological context, it is clear that transgenic crops have already had and will continue to have unintended ecological effects that can ultimately affect crop production through mechanisms such as gene flow, resistance evolution, community interactions, and production practices. No management option, including transgenics, is universally beneficial or detrimental. The ecological context of specific agroecosystems may improve predictions of the benefits, limitations, and consequences of a given management tactic within that system. As we increase our understanding of the ecological context of crop production problems, we may be able to improve our control efforts to maximize production and minimize potential problems in the future.     

Increasing Water Productivity in Rice-Based Systems in Asia – Past Trends,Current Problems,and Future Prospects

Abstract

Bioethanol is gathering attention as a countermeasure to global warming and as an alternative energy for gasoline. Meanwhile, due to the synchronous increase in bioethanol production and grain prices, the food-fuel competition has become a public issue. It is necessary to see the issue objectively and to recognize that the real background is the change in allocation of limited resources such as farmland and water. In this review, we discuss which, where and how energy crops shouldbe grown to establish a sustainable bioethanol production system. Several combinations of crops, areas and cultivation methods are recommended as a result of a survey of the bioethanol production system with various energy crops. In tropical and subtropical regions, sugarcane can be grown in agricultural and/or unused favorable lands. In other regions, cellulosic energy crops can be grown in abandoned and marginal lands, including lands contaminated with inorganic pollutant like heavy metals and some detrimental minerals. There also is the possibility that, for Japan and other Asian countries, rice can be grown as an energy crop in unused lowland paddy field. Regarding cultivation way, energy saving is beneficial for bioethanol production systems irrespective of energy efficiency. On the other hand, effective energy input should be consideredfor the systems with higher energy efficiency when available land area is limited. Exploring and developing new energy crops and varieties, which show higher biomass productivity and stress tolerances under marginal conditions, are necessary for sustainable bioethanol production because energy crop production would be restricted mostly to marginal areas in future.     

Improvement of Horticultural and Ornamental Crops Through Transgenic Manipulation of the Phytochrome Family of Plant Photoreceptors

Abstract

Consumer demands drive continuous developments in the production of horticultural and ornamental crops. In addition to improvements in quality and nutritional content, crop producers must supply an increased variety of products to a year-round market. The availability of many horticultural and ornamental crop products is dependent on the timing of reproductive development. The time at which many plants initiate sexual or vegetative reproduction is governed by a number of interacting environmental factors such as daylength, light quality and temperature. Artificial manipulation of the growing environment is therefore frequently used to ensure production meets retailers' marketing programs, a strategy which can often result in high energy costs. An alternative approach involves the manipulation of genes encoding proteins responsible for perceiving and transducing environmental stimuli, in particular, the genes encoding the phytochrome family of plant photoreceptors. Alterations in the expression of genes encoding phytochromes can modulate not only the timing of reproductive development, but also plant architecture. Such approaches can therefore be used to modulate a variety of phenotypic traits such as height, lateral branching and harvest yield, while enabling growers to tailor crop reproduction to their marketing needs. In this review, we will discuss examples of crop improvement using transgenic manipulation of phytochrome expression, along with benefits and disadvantages of such approaches.     

The Role of Nutrient-Efficient Crops in Modern Agriculture

Summary

Nutrient-efficient crops have an important role in modern agriculture. In the low-input systems that characterize most of world agriculture, nutrient-efficient crops improve crop productivity. In high-input systems of the developed world, nutrient-efficient crops are valuable in reducing pollution of surface and ground water resources from intense fertilization. Recent developments in molecular biology, root biology, rhizosphere interactions, and modeling present new opportunities for the understanding and improvement of crop nutrient efficiency. The degree and extent of nutritional limitations to crop productivity, and the economic and ecological liabilities of intensive fertilization, are such that eventually nutrient-efficient crops will be an important part of integrated nutrient management of cropping systems.     

Herbicide tolerant canola systems and their impact on winter crop rotations

Canola is widely grown in Australia to provide diversity within winter crop rotations. Its production is heavily reliant on triazine tolerant varieties but Clearfield^® and conventional varieties are also significant components of the industry. Glyphosate tolerant varieties have been introduced, thereby providing an alternative technology to be incorporated into the farming systems. To evaluate the potential impact of the relative herbicide technologies, a comparison of herbicide tolerant canola weed management systems was undertaken at Wagga Wagga, Australia over a 5-year rotation. Near isogenic lines of conventional, glyphosate tolerant and triazine tolerant varieties were evaluated for their abilities to control annual ryegrass (Lolium rigidum), the most challenging weed of temperate crops in Australia. Glyphosate tolerant and triazine tolerant canola achieved high levels of ryegrass control and attained higher yields than the conventional system. Glyphosate tolerant canola provided extra control of broadleaf weeds and also achieved better seed oil levels when compared with the other canola systems. There were positive flow-on weed management benefits for the remainder of the crop sequence from the weed control achieved in the initial crop, particularly following glyphosate tolerant canola. Subsequent control of volunteer canola in all treatments was readily achieved by using paraquat/diquat. The glyphosate tolerant weed management system was more profitable than the triazine tolerant system, although no allowance was made for technology costs as they were not known at the time of study. These outcomes demonstrate the potential value of herbicide tolerant canola to Australian farmers.     

Allelopathic Influence of Decomposing Wheat Residues in Agroecosystems

Summary

The concept that some crop plants have allelopathic effects is receiving greater attention as a potential mean that can be exploited in various ways for controlling agricultural pests. Wheat residues have been reported to inhibit growth of certain weeds, crops that follow wheat crop in crop rotation, soil nitrification and biological nitrogen fixation. Thus, crop production can be enhanced by avoiding the inhibitory effects or by exploiting favorable interactions. The present article presents an overview of research on the allelopathic influence of wheat residues in agroecosystems.     

Soil Salinity in South India: Problems and Solutions

SUMMARY

Soil salinity is assuming menacing proportions for production of agricultural and horticultural crops in South India. South India comprises of Andhra Pradesh (AP), Tamil Nadu (TN), Karnataka, Kerala, Goa, and Islands in Bay of Bengal (Andaman and Nicobar) and Arabian Sea (Lakshadweep). It comprises central uplands, Deccan plateau (Karnataka plateau and Telangana plateau of AP), Nilgiri hills of TN, South Sahiailri, Eastern hills (Eastern Ghats, TN, upland) and Coastal Plains. The rainfall ranges from 400 to 500 mm in AP, 450 to 1300 mm in Karnataka, 500 to 1215 mm in TN, 100 to 450 mm in Kerala. Climate is mainly semi-arid in nature. Red soils (Alfisols, Inceptisols, and Entisols) make up about 60–65% and are well drained, blacksoils (Vertisols and Inceptisols) comprise about 20–25% and the rest are coastal sands. Soil salinity problems are encountered in almost all the districts in Karnataka and AP. The area extends to about 0.176 million ha in AP, 0.2 million ha in Karnataka, 0.0427 million ha in TN and about 0.03 million ha in Kerala. Introduction of canal irrigation water and use of underground saline waters accelerated the appearance of salt affected soils. Soil salinity observed in South India ranges from hydrometphic saline soils in Kerala to highly saline (EC 20–30 dS m^?1) in Karnataka and AP. Saline soils were classified in to Natrargids or Solarthrids at subgroup level depending on the occurance of nitric or salic horizon within few centimetres of the surface. Soil salinity has reduced crop yields upto 50% and consequently cropping has been abandoned in many areas. Excess soluble salts can be removed through scrapping the surface salt crust or flushing and leaching or through subsurface drainage depending on the problem. Crops also vary in their ability to tolerate salinity at different stages of growth. In most crops subjected to irrigations with saline waters, germination and early seedling stages are generally the most sensitive and their tolerance increases with age. Salt tolerant varieties and nutrient management of crops in saline soils are important solutions for crop production under saline soils.     

稻田应用“水肥一体化”的现状、问题与思考

水肥一体化技术是在灌溉的同时将肥料混合施入土壤的集灌溉和施肥于一体的技术。发展和应用水肥一体化技术不仅可以达到节水省肥的目的,还是实现农业精确定量、智慧管理的重要途径。本文概述了水肥一体化在国内外的研究进展和水肥一体化中滴灌等技术在设施栽培以及玉米、棉花等作物生产中的应用现状。对滴灌技术在水稻中应用存在的成本高、环境不友好、品种适应性差等问题进行了分析,并提出对应的沟渠改造、加强滴灌管道建设、垄畦栽培结合、水肥药一体化和筛选新品种等解决方法。本文为水肥一体化在水稻栽培中的应用提供了参考,探索了水肥一体化水稻栽培未来的方向。     

Screening Cultivars at Low Dissolved Oxygen Level for Water-seeded Rice

Abstract

Eighteen local varieties of japonica rice and two japonica rice varieties introduced from Japan were studied to collect the basic information on the relationship between the amylographic characteristics and eating quality. The materials were planted in the first and second crop seasons of 1998 in central Taiwan. The pasting behaviors including peak viscosity, hot-paste viscosity, cool-paste viscosity, breakdown viscosity, setback viscosity, consistency viscosity, pasting temperature and the time to reach peak viscosity were measured. The eating quality of rice was evaluated by trained panelists in terms of overall palatability score. All amylographic characteristics except for hot-paste viscosity and overall palatability score varied significantly between the first and the second crops and the interactions between crops and varieties were also significant for all characteristics. Teikeng 2, Teikeng 3, Teikeng 4, and Teikeng 9 showed higher overall palatability scores than the other varieties in the first crop, and Koshihikari and Teikeng 6 showed the best overall palatability in the second crop, respectively. The coefficient of variation was higher in the second crop than in the first crop except the time to reach peak viscosity. Setback viscosity showed the highest variation in all amylographic characteristics. The heritability estimate was also higher in the second crop than in the first crop with the exception of consistency viscosity. The highest heritability values were given for consistency and breakdown viscositites in the first and second crops, respectively. However, the lowest heritability value was given for the time to reach peak viscosity in both crop seasons. The close relationship among peak, hot paste, and cool paste viscosities was found for both crops. The highest correlation coefficient was found between peak and breakdown viscosities in both crops. A significant negative correlation between breakdown viscosity and setback viscosity was observed in both crop seasons. Likewise, peak viscosity had a significant correlation with setback viscosity in both crops. In the first crop, the palatability score was negatively correlated with pasting temperature (r=-0.43**) but positively correlated with the time to reach peak viscosity (r=0.36*). There was a positive correlation between palatability score and peak viscosity (r=0.33**) and a negative correlation between palatability score and setback viscosity (r=0.34**) in the second crop.     

Allelopathy and Its Implications in Agroecosystems

Summary

Allelopathy includes both positive and negative effects of one plant on the other through environment, though most of the studies seem to focus on its deleterious impacts. It plays a key role in both natural and managed ecosystems. In agroecosystems, several weeds, crops, agroforestry trees and fruit trees have been shown to exert allelopathic influence on the crops, thus, affecting their germination and growth adversely. Some of the agricultural and horticultural crops affect their own seedlings grown in succession which is commonly known as replant problem/syndrome. Available studies indicate that allelochemicals act via bringing certain changes in physiological functions like respiration, photosynthesis and ion uptake. These, in turn, result in visible changes in seed germination, further growth reduction and overall performance of the target plants. The studies on interplant interactions assume significance in agroforestry programmes for selecting the types of crops complementary to the selective tree species. In the recent past, however, scientific attention has also been drawn to exploit the positive significant roles this phenomenon can play in enhancing crop productivity. In this context, we discuss the tremendous scope of allelopathy towards weed and pest management, apart from nitrogen conservation, and synthesis of novel agrochemicals based on natural product chemistry. The use of natural products of plant or microbial origin as pesticides/herbicides have gained much attention of the scientists as they offer many advantages over synthetic chemicals. The production of such chemicals should be enhanced by devising suitable protocols based on biotechnological procedures for their widespread utilization.     

Climate Change and CO2 Effects on Productivity of Danish Agricultural Systems

SUMMARY

Scenarios of climate change for Denmark suggest increases in annual mean temperature of 1 to 4°C by the end of the 21st century with an associated increase in rainfall of approximately 10%. The climatic warming and the associated increase in atmospheric CO₂ concentration will increase the productivity of agricultural crops. The increase may be slightly higher for indeterminate species, such as grass and other fodder crops, compared with cereals and other determinate species, where the duration of growth depends on temperature and daylength. The full benefits of the climatic warming requires adaptation in crop management, which at the individual crop level means changes in sowing dates, i.e., later sowings for winter cereals and earlier sowings for spring cereals. Some crop substitution will probably occur. On dairy farms more cereals will be grown due to higher productivity of the grasslands, which frees up some land for grain production. On sandy loam and loam soils spring cereals may become slightly more favorable and winter cereals slightly less favorable.     

Genetically modified sunflower release: Opportunities and risks

Sunflower (Helianthus annuus L.) is a crop native to North America for which there are no genetically modified commercial varieties. Some of the transgenic traits incorporated in other crops have already been subjected to research and experimentation in sunflower. Several new traits have also been noted, with the most relevant of these being the aim to increase latex production. GM sunflower release would modify crop management through improved mineral nutrition, weed control, insect and disease resistance, and product quality. In this research, the traits investigated were reviewed and analyzed in connection with main crop constraints. These characters could potentially influence agro-ecosystem components and produce a significant environmental impact. In regions where sunflower coexists with wild relatives this situation could affect germplasm resources, with this being especially important at the centre of origin and where Helianthus populations established in Africa, Asia, and Europe.     

Increasing Crop Competitiveness to Weeds Through Crop Breeding

Abstract

Increasing the ability of crops to compete against weeds, through either enhancing crop tolerance or crop interference to weeds, provides an attractive addition to current weed control practices and could be an integral component of weed management systems. Research has shown that considerable variability exists among crop culti-vars with respect to their ability to compete with weeds. Despite this evidence, directed research on competitive crops has been minimal. Reasons for this lack of emphasis in plant breeding programs include the effectiveness of current weed management with tillage and herbicides, and the lack of easily identifiable crop characteristics that are indicative of weed competitiveness. Expanded knowledge of specific crop-weed interactions would facilitate crop competitiveness to weeds through either crop management practices or plant breeding. Plant breeders need basic and applied information to identify favorable crop-weed competitive traits in order to enhance or incorporate those traits into crop cultivars. Accelerated research on weed competitive crops should lead to more economical, effective, and feasible integrated weed management programs for all crops.     

美国玉米生产技术特点与启示

从玉米品种熟期选择、农事操作及玉米生育进程、土壤耕作类型与整地、灌溉与施肥、绿色覆盖作物及精准农业技术等方面介绍美国玉米生产的技术特点,并比较分析中美玉米生产的气候条件、生育进程差异,提出高产与高效协同发展、简化农事操作、推进子粒收获等建议。     

Germplasm Enhancement and Breeding Strategies for Crop Quality in Japan

Abstract

Rice is the staple food for most Asians. Breeding efforts at the national and international levels have resulted in high-yielding varieties with resistance/tolerance to biotic and abiotic constraints. Consequently Asia has enjoyed rice self-sufficiency in recent years. Now in some countries over-production of rice has occurred, partly because of reduced rice consumption. For instance, in 1962 Japan had a per capita rice consumption of 118.3 kg and then this rapidly declined to about 60kg in 2003. Imbalances between production and consumption in rice and other crops have promoted a paradigm shift of breeding objectives oriented from producers to consumers. Germplasm enhancement (pre-breeding) and breeding strategies now focus on a broad range of crop and food qualities, which are closely associated with industrial and processing properties and human health and nutrition. In particular, physiological functions of chemical compounds involved in crop products are being studied as a part of breeding programs. Diverse plant genetic resources and advances in plant genome research have contributed to successful breeding strategies to improve and manage crop and food quality. Recent progress in germplasm enhancement and breeding strategies for quality improvement of rice, wheat, soybean and sweet potato in Japan is discussed.     

大豆主导品种、主推技术及其推广应用

2005年以来,农业部连续4年开展了大宗农产品主导品种、主推技术推介工作。4年间,共推介大豆主导品种22个、大豆综合配套栽培技术4项。主导品种和主推技术的推介,加快了新品种、新技术的推广速度,充分展现了科技对粮食增产、农业增效和农民增收的支撑作用。介绍了农业部推介大豆主导品种的类型、适宜区域和在生产中的比重和作用,分析了主推技术的要点和增产效益,比较了大豆主要品种与水稻、小麦、玉米、棉花、油菜等大田主要品种覆盖比例的大小。从主要品种占全国总播种面积的比例看,六大作物品种区域适应能力排序为：玉米〉小麦〉棉花〉大豆〉油菜〉水稻。作者提出,在今后的大豆育种工作中,应重点加强品种适应性的改良;在主导品种推介中,应适当增加大豆、水稻等光温敏感、区域性强、适应范围窄等作物的主导品种数目。     

Effect of Chinese Milk Vetch (Astragalus sinicus L.) as a Cover Crop on Weed Control,Growth and Yield of Wheat under Different Tillage Systems

Abstract

Reduced tillage systems are gaining popularity but weed control is often a limiting factor in the adoption of such systems. Cover crops have become a viable option for sustainable agriculture because of its contribution to soil fertility and improved crop performance. However, the contribution of cover crops to weed management is not clearly defined. We compared minimum tillage (MT) and no-tillage (NT) with conventional tillage (CT) for their effects on wheat growth in an original paddy land clay soil in the presence of Chinese milk vetch as a cover crop. Cover crop biomass, weed emergence, main crop growth and yield and soil penetration resistance were examined. Chinese milk vetch was successfully established under MT and CT but not under NT, which retarded its growth resulting in a significantly large biomass of all weed species. Weed suppression was more effective when the cover crop was broadcasted than row seeded. The presence of milk vetch as a cover crop significantly suppressed weed growth under MT especially at the late stage of growth and resulted in a comparable grain yield to that under CT. Although soil penetration resistance under MT remained high throughout the period of wheat growth, milk vetch could be effectively utilized as a cover crop under MT and wheat grain yield under MT was comparable to that under CT without mulch treatment.     

Ethylene

Abstract

Ethylene is a simple gaseous hormone that is involved in many aspects of plant growth and development. Two physiological responses that are commonly controlled by ethylene, fruit ripening and flower senescence, have been given the most significant attention in terms of crop improvement using the tools of modern plant molecular biology and biotechnology. Fortunately, the wealth of research on ethylene biosynthesis and signaling pathway has been providing tools for the genetic control of ethylene effects. Today, manipulation of ethylene biosynthesis and signaling is one of the most promising approaches to improve crops through genetic engineering. In this review we will discuss current status and future directions of transgenic techniques to control ethylene effects with a primary focus on flower senescence.     

The use of ultra-sonics in cellulose production from straw,grasses and similar material

Summary As oil seeds and cereals constitute important crops in many areas wherever agriculture is practized, the varied industrial requirements from products derived from these crops, provide a continuous stimulus for agricultural and industrial research.While progress has been made in developing varieties suited for different climatic conditions in the world, there is a pressing need for an intensified breeding program in which particular emphasis is placed not only on such features as an increased yield, earliness in maturity, high protein or oil content etc, but also on the suitability of straw and stalks for cellulose production. Therefore an attempt was made to analyse sunflower stalks for their suitability as a source for -, -and -cellulose. Besides that we were able to show that Ultra-Sonic waves can induce favorable biochemical reactions, it was logical to try if by means of such sonic treatments sunflowers could become an important source for paper-pulp and textile fiber, and become herewith a double purpose crop.