Nutrient efficiency in wheat is very complex. It includes two major types: nutrient acquisition efficiency and nutrient use efficiency. Various studies on wild, landraces, old, intermediate and new genotypes of cereals showed that the new varieties produced higher grain yields than the old varieties, and were also more efficient at using nutrients. Several spring wheat cultivars, representing almost all cultivars of spring wheat, released from the Federal Office for Cultivar Registration, Germany and published in the ‘Descriptive List of Cultivars’, were used to investigate the interactive effects between genotypes and the use efficiencies of the three macro nutrients N, P and K by the grain and straw. The results obtained in this study indicate that nutrient use efficiency of the single nutrients varies widely within recent cultivars. Some cultivars were identified as being multiple-nutrient use efficient. These are considered low-input cultivars. It appears that a special breeding programme of crop cultivars for low nutrient and stress conditions could be successful. Improved cultivar response to nutrients will help to reduce inputs and hence protect the environment.

Different rice modern varieties (MV) may differ in their nutrient concentration, nutrient uptake and absorbed nutrients for grain production. These nutritional problems are not well addressed particularly in Bangladesh where 41% of 10 million hectare rice lands are covered with MV rice. This investigation was made in 1996 dry season under irrigated conditions on an Aeric Haplaquept soil at the Bangladesh Rice Research Institute Farm with five popularly grown MV rices-Purbachi BR1, BR3, BR14 and BR29. Straw and grain yields of the five rice varieties ranged between 3.90 to 4.66 adn 3.91 to 5.07 t haE-1, respectively. The highest straw yield was found in Purbachi,while BR29 produced the highest grain yield. The lowest straw and grain yield was obtained by BR3. However, there was no significant difference in straw and grain yields among the tested varieties (p more than 0.05). The tested varieties showed significant differences (p less than 0.05 or p less than 0.01) in content, uptake and internal efficiencies of some major nutrients. Straw N,P,Ca and Mg and grain P, Ca and S concentration differed significantly among the tested varieties, while there was no difference in straw and grain K content. There was noticeable difference among the MV rices in total uptake of K, Ca, Mg and S but not of N and P although P uptake by grain was different among the varieties. Utilization of absorbed nutrient to produce grain, internal efficiency, was different in tested varieties for P, Ca, Mg and S but not for N and K. BR29 proved to be the best P and Mg efficient variety while BR14 was the highest Ca and S efficient. Purbachi and BR1, the two oldest MV rice in Bangladesh, were the least S and P efficient, respectively.

Early- maturing varieties of maize 'Bonny', 'Mutin' and 'Diamand' (KWS company, Germany) were investigated at the Lithuanian Institute of Animal Science under meteorological conditions of 1996. The investigation indicated that 'Mutin' variety of maize was most productive and yielded 118.27 cwt of dry matter/ha, 10857.2 feed units and 6.33 cwt of digestible protein. The silage made from 'Mutin' maize was of the highest quality. Estimations of fresh maize yield, nutrient losses of silage, nutritive value of feed and amount of digestible protein indicated that 'Bony', 'Diamant' and 'Mutin' varieties of maize yielded, respectively, 10.11, 8.59 and 10.22 tonnes of dry matter, 7975.8, 8251.8 and 8970.9 feed units, and 559.9, 485.1 and 540.6 kg of digestible protein.

The response of wheat (Triticum aestivum L.) to macroelement fertilization was investigated on a large number of trials, with 195 short-stem varieties and 58 long-stem varieties. The results have shown that fertilization rates exceeding 195 lb N/acre do not result in higher yields. Economically optimum fertilizer rates were 158 lb N/acre for short-stem varieties and 139 lb N/acre for long-stem varieties. Analysis shows that the economic profit for a given yield curve is a function of the ratio of fertilizer cost to the price of product. This ratio cannot be higher than 9.75 for short-stem wheat varieties or higher than 14.5 for long-stem wheat varieties. Research QuestionFarmers supply enough fertilizer to meet the nutrient needs of their crops, but in most cases they have been following a higher fertilizer application rate for many years. In Greece, the wheat crop recovers close to 50% of the fertilizers used. The primary objective of this research was a systematic approach of wheat production with a more rational policy on N fertilization. Literature SummaryMany studies have been conducted in order to promote a better fertilization to secure higher yields of wheat grain production, and to alert people of the possible deterioration of water quality and natural resources. The most important fertilizer is N, and our attempts are focused on the effect of this nutrient in wheat grain production, leading to a maximum net return. Study DescriptionExperiments were conducted all over Greece for the last 10 consecutive years. Furthermore, the effect of N and its combination with P and K was studied. Wheat varieties: long stem and short stem Soil: Hilled and plano Weed control: Basagran, MCPA Treatments: Table 1 Applied QuestionsDid the production curve have a positive indication on the wheat grain production? In this research, all N fertilization levels led to an increased grain yield, following a diminishing return yield curve. This was clearer in the short-stem wheat varieties, than in long stem ones. In both cases, the maximum output was observed at the same fertilization rate (195 lb N/acre). Applying P in addition to any N rate had little effect on crop yield. Is the maximum economic return related to change of wheat grain and fertilizer prices? Starting from the ratio of wheat grain prices to the prices of fertilizers at 2.75, experimental data showed that long stem varieties are more sensitive to any increase of the above ratio, while short stem varieties have a double tolerance (Fig. 1). Presently, maximum net economic retum is achieved by applying ≅140 and ≅160 lb N/acre for long stem and short stem wheat varieties respectively. RecommendationWe recommend a fertilization level of ≅140 and 460 lb N/acre for long stem and short stem winter wheat varieties respectively. This will result in the highest net economic return. Fertilization rates beyond these levels should be avoided because of the decreasing net profit and the potential deterioration of water resources. Table 1Fertilization rates in wheat crop. Applied N, Ib N/acreGroups of wheat varieties0,81, 134, and 161Short stem0,54, 81, and 108Long stemFig. 1Maxium net economic return.

Seven cotton (Gossypium hirsutum L.) varieties were evaluated for growth and utilization efficiency of nitrogen (N) and phosphorus (P), in hydroponics using modified Johnson's solutions containing adequate (6.0 mM N and 0.20 mM P), and deficient levels of N (0.8 mM) and P (0.01 mM). Substantial differences were observed among varieties for accumulation of shoot dry weight (SDW), relative reduction in shoot biomass due to N-deficiency (NSF), and uptake by shoot in case of N, and root dry weight (RDW), root:shoot ratio (RSR), relative reduction in shoot biomass due to P-deficiency (PSF), concentration in shoot and uptake by shoot in case of P. Variety SLS-1 exhibited the minimum stress at N-deficiency (NSF = 34%) as well as P-deficiency (PSF = 59%) among all the varieties. A negative correlation (r = 0.555, n = 35) between SDW and RSR in P-stressed plants suggested increase RDW production at the cost SDW. Utilization efficiency in varieties remained unchanged in case of N-deficiency stress and decreased in case of P-deficiency stress as compared to control, and in both the cases differences among varieties remained statistically non-significant. Nutrient level X variety interaction was significant for all the parameters studied in case of P, whereas for N, the interaction was significant only for shoot dry weight, stress factor and uptake by shoot.

Potato virus S (PVS) was eradicated from systemically infected plants of eight potato hybrids and four potato varieties in culture in vitro: cultivation in a nutrient medium containing ribavirin, a synthetic riboside, was used. Virus concentration decreased gradually, after repeated subcultures of the top parts of plants to a ribavirin-containing medium. Effects of the concentration used, subculture number and treated variety were manifested. The highest number of virus S free regenerants was determined in media with ribavirin concentrations 0.002 and 0.003 %. Positive sanitation effects were observed from the second subculture in the separate varieties, the proportion of virus-free clones ranged from 55 to 100 % following the third subculture. No virus was detected by ELISA after regenerants were transplanted into greenhouse conditions. This method provides results comparable with those obtained by usual procedures of virus S eradication.

Variations in the copper, iron, zinc, manganese, calcium, magnesium, sodium, potassium and phosphorous content of fresh white asparagus (Asparagus officinalis, L.) as a function of the spear portion and the differences between varieties (Desto and Cipré's) and thicknesses (< 11 and >14mm) of asparagus were investigated. The mineral elements studied showed significant changes between the ten portions into which the spears were cut, with lower concentrations, except for sodium, occurring in the asparagus portions furthest away from the tip of the spear. These changes between portions signified a greater nutritional value of the apical spear area (6 cm from the asparagus tip) according to the higher percentages of mineral RDAs supplied in the apical portions. The varieties and thicknesses of white asparagus investigated showed this diminishing distribution of the mineral content throughout the spear and displayed significant differences for the majority of the mineral elements between varieties and thicknesses, although these differences were minimal and did not have any nutritional significance since the percentages of mineral RDAs supplied were similar. Nutrient density was well over 100% for all the elements, except for sodium, and these results indicated that fresh white asparagus, if consumed in sufficient quantities, contributes substantially to the intake of these mineral elements.

Murashige & Skoog nutrient was supplemented with substances of molecular weight (MW) less than 5 kDa, which were separated from extract of winter wheat ears by means of Sephadex G-25 ultrafiltration. Isolated embryos of the same wheat cultivar (Grana) were vernalized in the nutrient for 0 and 7 days at 2 °C for 2 weeks and planted in a glass-house. After 150 days of growth (20/17 °C day/night) the development of the shoot apices was observed. It was found that substances of MW<5 kDa strongly stimulated the generative development of the plants, enabling the earing of 30 % of non-vernalized plants (control=0%) and 100 % plants vernalized for 7 days (control=29 %).The substances present in the extract of both spring (cv. Jara) and winter (cv. Grana) varieties were fractionated by means of Sephadex chromatography into 300 fractions of MW=1 to 5 kDa and each of them was added to the isolated embryos of cv. Grana. The embryos were vernalized at 2 °C for 7 days and then cultured as previously described. It was found that the differentiation of the shoot apices was stimulated by over 34 % by fractions of winter wheat extract and more than 50 % by fractions of the spring wheat extract. However, only a few of identical fractions of the extracts of both wheat varieties were able to induce the earing of the plants. These fractions were grouped in 4 continuous intervals of MW equal to about 4.5–4.9, 3.2–3.3, 2.1–2.6 and 1.00–1.03 kDa. Within the three intervals was identified a small group of identical fractions, which affected the growth of the seedlings in similar mode i.e. inhibiting or stimulating. Thus it can be assumed that these intervals contained identical or similar substances capable of stimulating strongly the earing of winter wheat.

A participatory rural appraisal on Striga was conducted during Febrary-March 1996 in the northern Ethiopian highlands. The main objective was to provide information on the farming systems, Striga status and control methods. A total of 108 farmers were interviewed and they identified Striga as one of the major constraints to increasing agricultural productivity. Most farmers are aware that Striga is found in nutrient depleted soils and that improved soil fertility alleviated the problem. They identified cultivation, stored grain, crop residues, erosion runoff, livestock and man as Striga dispersal methods. Fallowing, intercropping and crop rotation with trap crops are not practiced in the area are hand pulling, ox-plow cultivation and use of manure close to the homestead. Long-term research efforts should be directed towards reducing the Striga seed bank in the soil, integrated nutrient management strategies, cropping systems and multipurpose trees that improve soil fertility, decrease weeds, pests and the incidence of plant diseases. Breeding and screening for resistant cereal varieties should be conducted. The development of integrated control measures will require a farming systems approach in order to identify problem areas and the types of control measures that are likely to be acceptable to the farmers.