Modern spring barley varieties have been developed with the aim of combining high productivity and standardised product quality under high-input conditions using pesticides for control of weeds, diseases and insects as well as heavy application of nutrient-rich and water-soluble inorganic fertilizers. In the organic growing system, biotic and abiotic stresses have to be overcome by growing the appropriate varieties and by practicing good farm management. The important spring barley traits to be considered in organic farming are related to the inherited viability and adaptation of plants to survive biotic and abiotic stresses and includes competitive ability (morphology, weed tolerance, growth rate, allelopathy), disease resistance (morphology, specific and non-specific resistance proporties, disease tolerance) and nutrient acquisition ability (root morphology, nutrient uptake and use efficiencies, low-nutrient tolerance, symbioses). An important question is whether modern spring barley varieties possess the right combinations of these characteristics to ensure a stable and acceptable yield of good quality when grown under different organic growing conditions. We know that varieties often perform and yield differently in different environments due to genotype-environment interactions, so it may be important to evaluate characteristics of varieties in organic as well as in conventional farming systems. However, it remains unclear to date whether the differences between the conventional and the organic growing systems are large enough to justify breeding and testing of varieties in both environments. Extensive field experiments and refined statistical methods are needed to clarify this. Characterisation of varieties as part of the official variety testing is at present done under conventional farming conditions in Denmark. The aim of a newly started inter-institutional Danish research project within The Danish Research Center for Organic Farming (DARCOF) with project participants from The Royal Veterinary and Agricultural University, Danish Institute of Agricultural Sciences and Risø National Laboratory is to Identify combinations of plant characteristics required for a barley crop to be successful in organic growing systems and develop methodologies for measuring these characteristics. Evaluate, by investigating genotype-environment interactions, the need for specific variety trials for organic farming, and if necessary implement such trials. Improve yield and yield stability in different organic farming systems by strategic use of the appropriate varieties and variety mixtures. Investigate the potential of different variety mixtures for reducing diseases and weeds and increasing nutrient uptake efficiency. Obtain new knowledge on plant competition, disease complexes, epidemiological models, nutrient acquisition and associations between molecular markers and agronomical traits. The results of the first-year trials on three organic workshop areas and in two conventional fields with about 120 mostly modern varieties and a few variety mixtures will be discussed. The preliminary analyses indicate large variation in yield between the different varieties.

A field study was carried out with three fibre crop varieties to estimate the bulk organic materials produced by each variety and soil nutrient status due to their incorporation into soil. Considerable amount of plant biomaterials were produced by all varieties viz., CVL-1(6.4t ha-1), 0- 9897(7.56t ha-1) and HC-95(9.02t ha-1. Plant biomaterials of each variety enriched the soil nutrient status over the initial value. Highest nutrient status (OC-1.7%, OM-2.95%, N- 0.58%, P-23 ppm, K-0.79 meq/100) was found for variety HC-95. The highest percent increments of these nutrients over the initial nutrient of soil(INS) and not allowed to decompose the plant biomaterial in soil (NBM) [OC over INS (211 %), NBM 1159%); N over INS (190%), NBM (81 %); K over INS (93%), NBM (72%)) were found with variety HC-95. The highest P(28 %) was obtained with 0-9897 where percent increment of P over INS and NBM was 115%. In production of biomaterials and enrichment of soil, Kenaf performed better than Jute varieties. The cultivation of jute and Kenaf may be an exceptional source of organic materials which may save the depleted soil of Bangladesh without using external organic matter.

Farmers are interested in hydroponic tomato cultivation because of the high demand of high quality products by the consumers. Three trials here carried out under greenhouse conditions in Marília, SP, Brazil, using the hydroponic nutrient film technique, in order to evaluate yield and quality of long-life salad tomato (Lycopersicon esculentum) varieties, during 1998 and 1999. Four varieties (Carmen, Diva, Graziela, and Vita) were tested using a randomized block design, with six replications. The variety x crop season interaction effect was significant, meaning that varieties have distinct performances during the different cropping seasons. The Vita variety presented commercial valid yield, with mean fruit weights higher than the other varieties.

Leaf chlorophyll content is closely related to leaf nitrogen (N) content, so it is reasonable to assume that NH4-N:NO3-N ratio in the nutrient solution used to grow tomatoes (Lycopersicon esculentum Mill.) hydroponically may affect leaf greenness, and consequently chlorophyll meter (SPAD) readings. It has also been shown that increasing nutrient solution strength (NSS) increases tomato productivity, but there are no reports regarding how NSS affects SPAD readings under greenhouse conditions. Genotype may also influence SPAD readings, and standardization for cultivar and sampling time may be needed. The objective of this study was to characterize SPAD readings for five tomato cultivars, and SPAD reading response to a combination of two nutrient solutions strength (NSS) (1X and 4X Steiner solution strength daily applied 18 days after transplanting at 7 p.m.) and two concentrations of NH4-N in solution (0 and 25%) in order to evaluate the potential of SPAD readings as a tomato yield predictor in greenhouse production systems. The SPAD readings were not uniform across tomato varieties tested, being consistently higher for "Max" and lower for the other varieties. Initially, SPAD readings for tomato varieties used in this study were low at the vegetative stage, and increased up to 40 days after transplant (DAT), but subsequently decreased at 49 DAT, or the fruit set of the first and second clusters. After this time, SPAD readings showed no variation. Chlorophyll meter readings for Max were higher in the top plant layers, but decreased in the top plant layer of the other tomato varieties. The SPAD readings were higher for plants supplied with 25% NH4-N than those without NH4-N in solution, but the use of a nighttime nutrient solution did not affect SPAD readings. None of the possible interactions among tomato variety, NH4-N:NO3-N ratio, and NSS were consistently significant. SAPD readings may be useful in monitoring low or high supply of N in greenhouse grown tomato plants.

Biotechnology strategies are now available to improve the amount and availability of nutrients in plant crops. Those strategies include simple plant selection for varieties with high nutrient density in the seeds, cross-breeding for incorporating a desired trait within a plant, and genetic engineering to manipulate the nutrient content of the plant. In plant cross-breeding, all genes of the parent plants are combined and the progeny have both desirable and undesirable traits. To eliminate undesirable traits, plant breeders «back-cross» the new plant varieties with other plants over several generations. This technique, called hybridization, has been used to create varieties of low-phytate corn, barley, and rice. Using the techniques of genetic engineering, the gene(s) encoding for a desired trait(s) in a plant are introduced in a precise and controlled manner within a relatively short period of time. Golden rice, containing carotenoids, and rice with higher amounts of iron, are two examples of genetically engineered plants for improved nutrition. Genetic engineering has tremendous potential for revolutionizing nutrition. However, public concerns regarding safety, appearance, and ethics must be overcome before these products can be effectively introduced into the food supply.

The relative susceptibility of five wheat varieties viz., Inqlab-91, Punjab-96, MH-97, Watan and Parwaz-94 to Rhyzopertha dominica (F.), was studied under the laboratory conditions at 30 degree centigrade and 70% relative humidity. The percentage grain damage and weight loss used as an index of susceptibility, indicated that variety Watan suffered significantly comparatively less weight loss (21.62%) and grain damage (34.8%) as compared to rest of the varieties, viz., Inqlab (25.17%; 39.80%), Punjab-96 (26.58%; 39.80%), MH-97 (20.0%; 40.80%) and Parwaz-94 (24.26%; 41.0%). Chemical analysis of the infested grain showed significant differences in the nutrient losses in the test varieties. Variety Watan suffered less loss as compared to other varieties, which were not significantly different from one another. Similarly the results of the free choice experiment did not show significant differences in the preference Rhyzopertha dominica to different wheat varieties.

Planting Al tolerant crops is an economically justifiable approach in crop production on acid soils. Experiments were conducted to study the mechanisms of Al tolerance among species and varieties of tropical rice, maize, and soybean with previously known levels of Al tolerance. These varieties were hydroponically cultured in 0, 5, 10, and 30 mg/l Al with complete nutrient solution at pH4. The results showed that root/shoot ratio of dry weight at 10 mg/l Al treatment was an important parameter to indicate differential Al tolerance in maize. Oxalic acid exudation from roots cannot always explain the Al tolerance. Total organic acid concentration in roots at 10 mg/l Al treatment indicated a different of Al tolerance in soybean and lowland rice. Aluminium translocation from roots to shoots was lower in tolerant varieties than in sensitive varieties of soybean. Increased Al concentration in shoots with increased Al level in the solution was larger in soybean and maize than in lowland or upland rice. Among varieties of soybean, the Al concentration in shoots increased drastically in Wilis (Al-sensitive variety) with increasing Al level, but it did not in Kitamusume (Al-tolerant variety)

Improved varieties of legumes adapted to nutrient deficiency have the potential to improve food security for the poorest farmers. Tolerant varieties could be an inexpensive and biologically smart technology that improves soils while minimizing fertilizer costs. Yet other technologies that improve productivity and appear to be biologically sound have been rejected by farmers. To translate benefits to smallholder farmers, research on low-nutrient tolerant genes and crop improvement must keep farmer preferences and belief systems in the forefront. We review farmer participatory research on legume-intensification and soil fertility management options for smallholder farmers in Africa, including recent results from our work in Malawi and Kenya. We suggest that indeterminate, long-duration legumes are the best bet for producing high quality residues, compared to short-duration and determinate genotypes. This may be due to a long period of time to biologically fix nitrogen, acquire nutrients, photosynthesize and grain fill. Also, the indeterminate nature of long-duration varieties facilitates recovery from intermittent stresses such as drought or pest pressure. However, indeterminate growth habit is also associated with late maturity, moderate yield potential and high labour demand. These traits are not necessarily compatible with smallholder criteria for acceptable varieties. Malawi women farmers, for example, prioritized early maturity and low-labour requirement, as well as yield potential. To address complex farmer requirements, we suggest the purposeful combination of species with different growth habits; e.g. deep-rooted indeterminate long-duration pigeonpea interplanted with short-duration soyabean and groundnut varieties. On-farm trials in Malawi indicate that calorie production can be increased by 30% through pigeonpea-intensified systems. Farmers consistently indicate strong interest in these systems. In Kenya, a 55% yield increase was observed for a doubled-up pigeonpea system (a double row of pigeonpea intercropped with three maize rows) compared to traditional, low density intercrops. However, the need for improved pigeonpea varieties with high intercrop suitability, including reduced early branching, was highlighted by a farmer preference study in the same area. These examples illustrate the potential for participatory research methodologies to drive biophysical research in farmer-acceptable directions.

Field experiments with different varieties under different root cutting (root was cut from one, two, or three sides of the rice plant and no cutting) at the heading stage were conducted on their effect on yield and yield components. The results showed that root cutting increased root activity significantly at the ripening stage in general, irrespective of varieties and treatments. One side cutting caused a yield increase in four varieties (Guang-Lu-Ai 10.2%, Pei-Za-72 4.6%, Feng-Ai-Zhan 1 12.8%, Te-San-Ai 11.4%) and a decrease in one (Er-Qing-Ai by 18.2%). The difference was mainly associated with a difference in grains per panicle and percentage filled grains. Two side cuttings (T2) and three side cuttings (T3) caused a yield increase in two varieties (Guang-Lu-Ai and Te-San-Ai) and a decrease in three (Er-Qing-Ai, Pei-Za-72, Feng-Ai-Zhan 1). It can be concluded that light root cutting at the heading stage has no significant effects on rice yield. It can even increase the yield of some varieties. This may be because root cutting can increase root activity at maturity, which is important for improving the ability to absorb water and nutrient and delay the plant from senescence.

Preliminary studies on the spatial variability in available nutrient content in agricultural fields under both large scale and small scale operation in China were conducted, and the different technical approaches to realize site specific nutrient management developed. Results indicated that significant spatial variability of all essential plant nutrient exist in different operating systems and at various scales. Under small scale operation within the family responsibility system, in which each farmer's family is assigned to operate one or several small field plots with the field size normally less than one hectare, the large spatial variability of soil nutrients was mainly attributed to the fertilizer history of individual farmers, diversity of crop types and varieties used in relatively small scale field management. Significant correlation was found between crop yields and available soil nutrient levels at the corresponding sites in the field. Based on the understanding of the nature of spatial variability of soil nutrient availability in China, and with the purpose of increasing profitability and sustainability of crop production, a site-specific soil nutrient management strategy is proposed. Related techniques and agricultural services are discussed, including soil testing and fertilizer recommendation, farmers' plot specific or regional specific fertilization approaches and related services at national and regional levels.