Stem Dry Matter Research Articles

Effect of Deheading on Juice Quality Characteristics and Sugar Yield of Sweet Sorghum

A field experiment involving 10 sweet sorghum cultivars was undertaken to study the effect of panicle removal at anthesis on juice quality characteristics and sugar yield in sweet sorghum; control plants were left intact. The plants were harvested at grain maturity, and juice extracted from the millable stalk was analysed for sucrose contact (Pol percentage), brix and purity. Deheading treatment resulted in significant increases in millable stalk and sugar yields over those of the intact control plants. As a result of panicle removal, stem dry matter accumulation increased and side tillers were generated. The amount of juice extracted increased in the treated plants, but sucrose (Pol percentage), brix and purity levels in the juice were reduced in comparison with the intact plants.

Agronomy of fibre hemp ( Cannabis sativa L.) in Europe

Fibre hemp may yield up to 25 t above ground dry matter per hectare (20 t stem dry matter ha −1) which may contain as much as 12 t ha −1 cellulose, depending on environmental conditions and agronomy. Its performance is affected by the onset of flowering and seed development. Effects of cultivar and management on yield and quality were tested at three contrasting sites in Italy, the Netherlands and the UK in three years, making use of standardised protocols for experimental design and research methodology. Highest yields (up to 22.5 t dry matter ha −1) were obtained in Italy when later cultivars were used. Attainable yields proved slightly lower in the Netherlands and much lower in the UK. The quality of the cellulose was relatively stable over the growing season, but lignification may proceed rapidly some time after flowering. Crop development was very rapid and crops maintained green leaf area for a long time, thus radiation interception was considerable. The radiation use efficiency changed during development. It was lower after flowering (about 1.0 g MJ −1 PAR) than before (about 2.2 g MJ −1 PAR). Growing earlier cultivars to obtain some seed set advanced the reduction in radiation use efficiency. Nitrogen proved to affect yield only slightly. A relatively small amount of fertiliser will be adequate to cover the crop’s needs. Plant density declined during growth in a site-specific manner when it was high initially. Very low plant densities may not show this self-thinning but reduced yield and (especially) quality. Final plant densities were proven to depend more on initial plant stands than expected from literature. This was true at all three contrasting sites and in the different years. Nitrogen and plant density hardly interacted within one site. Results suggest that hemp can yield large quantities of useful cellulose when ecologically adapted cultivars are sown in proper plant densities. The cultivation is environmentally friendly with little harmful accumulation or emission of chemical inputs. More research on ideotyping is required and breeding efforts should be broadened.

Crop yield and quality parameters of four annual fibre crops (hemp, kenaf, maize and sorghum) in the North of Italy

Four fibre crops (hemp, kenaf, maize and sorghum) considered amongst the most suitable for the conditions of Northern Italy were compared in 1995 and 1997, over two irrigation regimes (rainfed conditions and restoration of 100% ETp) and in two locations (Bologna and Milano). Three harvests were carried out on each crop at different development stages. At each harvest time data on yield and yield components were collected. Sub-samples of stems of each crop and at each harvest time were analysed following the Van Soest method. On average, fibre sorghum proved to be the higher yielding crop. It produced 26.2 Mg ha −1 of total dry matter of which 18.1 Mg ha −1 was partitioned to the stems. Fibre maize produced more total dry matter than kenaf (19.0 Mg–15.7 Mg ha −1) but dry matter accumulated to stems was higher in kenaf (10.8 and 13.4 Mg ha −1). On average, fibre hemp yielded 14.0 Mg ha −1 of total dry matter and 10.9 Mg ha −1 of stems. This result was highly affected by the low hemp production in Bologna in 1995, where unfavourable conditions, in the first phases of cultivation, resulted in a stunted establishment of the crop (18.7 Mg ha −1 of total dry matter in Milano and only 8.3 Mg ha −1 of total dry matter in Bologna). On all crops, irrigation produced a slight increase in total biomass (7%) and in stem dry matter (9%) compared to the rainfed condition. In both locations, yield increase due to irrigation was larger in maize and kenaf, than in hemp while, in 1995, it caused a severe lodging on sorghum. The four species proved to be different for growth rates, patterns of development and particularly for cellulose, hemicellulose and lignin content of stems. Cellulose content varied between 56–66% of stem dry matter in hemp, 46–57% in kenaf, 35–45% in maize and 39–47% in sorghum. As harvest time was delayed, cellulose content tended to increase for hemp and kenaf while it decrease for sorghum and maize. Hemicellulose content of hemp and kenaf stems varied between 16–19%, while it varied between 26–29% in sorghum and maize. Hemicellulose content decreased with irrigation and with delay in harvest time. Lignin content in hemp stem ranged between 8 and 13%, it was 6.9% in kenaf and maize, and ca 8% in sorghum.

Variations in nitrogen uptake and nitrate-nitrogen concentration among sorghum groups

Nitrogen uptake and nitrate-N concentration in forage sorghums, which are related to ground water pollution or feed quality under conditions of crop fertilization by only animal wastes, were examined. Seventy-four genotypes of sorghum and Sudan grass were tested. They were classified into 4 groups; grain type and dual purpose type sorghums (6 and 13 genotypes, respectively, Sorghum bicolor Moench), sorgo type sorghum (21, S. bicolor), Sudan type sorghum (22, S. bicolor × S. sudanense (Piper) Stapf), Sudan grass (12, S. sudanense). There was a strong correlation between dry matter (DM) yield and N uptake, with the sorgo type producing the highest DM matter yield and showing the highest N uptake. Nitrate-N, which causes nitrate poisoning of ruminants, was detected mostly in the stem of all the genotypes. The nitrate-N concentration based on DM could be calculated accurately by multiplying the nitrate-N concentration of stem on a fresh matter basis by the DM partitioning ratio of stem divided by the DM concentration of stem. The grain type and the dual purpose type of sorghums with dry stem showed the lowest nitrate-N concentration because these plants had a lower DM partitioning ratio of stem and higher DM concentration of stem. Sudan grass and Sudan type sorghum with the genetic background of Sudan grass showed higher nitrate-N concentrations owing to their ability to accumulate nitrate-N.

MANEJO DA IRRIGAÇÃO E DA ADUBAÇÃO NITROGENADA NA CULTURA DO ALGODOEIRO HERBÁCEO

RESUMO O estudo foi conduzido de maio a outubro de 1996, em galpão coberto, no CCA/UFPB; no município de Areia, PB, com o objetivo de se avaliar o efeito dos níveis de água disponível no solo (AD), 75, 50 e 25%, e de nitrogênio, 0, 40, 80, 120 e 160 kg ha-1 de N, sobre algumas características do algodoeiro herbáceo, cv. CNPA-7H. Para tanto, utilizou-se o delineamento de blocos ao acaso, em esquema fatorial 5 x 3, com 3 repetições. Houve efeito linear significativo (p ? 0,01) positivo do N sobre a área foliar, rendimento de algodão e evapotranspiração e efeito quadrático sobre a produção de matéria seca. O nível de 25% da AD causou efeito depressivo (p ? 0,01) sobre o diâmetro de caule, altura de plantas, área foliar, evapotranspiração e matéria seca. Não houve interação (p > 0,05) entre os níveis de N e AD, sobre as variáveis estudadas.

Dynamics of nitrogen and dry-matter partitioning and accumulation in broccoli (Brassica oleracea var. italica) in relation to extractable soil inorganic nitrogen

The effects of six rates of N fertilization (0, 125, 250, 375, 500 and 625 kg N ha−1) on the dynamics of N utilization relative to extractable inorganic N in the soil profile were determined for broccoli in three growing seasons. The amount of pre-existing extractable inorganic N in the soil was lowest for the spring planting, followed by the early-summer then late-summer plantings. During the first 2 wk after transplanting, plant dry-matter (DM) and N accumulation rates were low, and because of the mineralization of soil organic N the extractable soil inorganic N increased over that added as fertilizer, especially in the top 30 cm. From 4 wk after transplanting until harvest, DM and N accumulation in the plants was rapid and corresponded to a rapid depletion of extractable inorganic N from the soil. At high N-fertilization rates, leaf and stem DM and N accumulations at harvest were similar among the three plantings. However, the rates of accumulation in the two summer plantings were higher before and lower after inflorescence initiation than those in the spring planting. Under N treatments of 0 and 125 kg ha−1, total N in leaf tissue and the rate of leaf DM accumulation decreased while inflorescences developed. There was little extractable inorganic soil-N during inflorescence development in plots receiving no N fertilizer, yet inflorescence dry weights and N contents were ≥50 and ≥30%, respectively, of the maxima achieved with N fertilization. These results indicate that substantial N is translocated from leaves to support broccoli inflorescence growth under conditions of low soil-N availability. Key words: N translocation, N fertilizer

Groundnut ( Arachis hypogaea) for food and fodder in crop-livestock systems: forage and seed yields, chemical composition and rumen degradation of leaf and stem fractions of 38 cultivars

Forage and seed yields of groundnut ( Arachis hypogaea) are considered to be joint products by crop-livestock farmers, but forage yield and quality are not currently part of selection criteria in groundnut improvement programs in West Africa. Variations in forage and seed yields of 38 late-maturing groundnut cultivars were determined in 1995 and 1996 at Samaru, Zaria, northern Nigeria. Crude protein (CP), neutral detergent fibre (NDF), in sacco degradation of dry matter (DM), and nitrogen (N) were also estimated. Average yield of forage (4547 ± 1087.9 kg ha −1) and seed (1247 ± 266.6 kg ha −1), leaf : stem ratio (34 ± 9.4%), CP, NDF, and DM degradation of leaf and stem varied ( P < 0.05) among cultivars. Average (g kg −1 DM) leaf CP (158 vs. 111), soluble (262 vs. 181) and degradable (512 vs. 407) DM fractions, potential degradability (PD) (774 vs. 588) and effective degradability (ED) (542 vs. 429) were higher than those of the stem. Forage and seed yields were significantly correlated ( r = 0.53), but seed yield was poorly correlated with forage quality indices examined. It is therefore suggested that plant breeders could select genotypes with higher seed and forage yield, and better forage quality. There were significant but weak correlations between leaf CP ( r = 0.32) and stem NDF ( r = −0.33) with leaf : stem ratio, and ED of leaf and stem with DM loss after 48 h of rumen incubation. Based on yield (forage and seed) and effective degradability of leaf and stem fractions, cultivars were identified with high (e.g., 42–85, M354–81, UGA-2, RMP-12,), medium (e. g., UGA-5, 59–85 A, M170–80 I) and low (e. g., 176–85 A, UGA-11, ICGV.86347) potential for seed and forage production.

Influence of fungal endophyte infection on nutrient element content of tall fescue

Fungal endophytes infect several grass species. The fungus can alter the growth, and physiological and morphological characteristics of the infected plant. A greenhouse experiment was designed to determine the effect of the fungal endophyte Neotyphodium coenophialum on the nutrient element content of a selected ecotype of tall fescue (Festuca arundinacea), when growing at two nutrient element supply levels. Stem dry matter, averaged over all harvests and nutrient element supply treatments, was higher in non‐infected (E‐) than in endophyte infected (E+) plants. We found a significant interaction between endophyte infection and nutrient element supply level and/or harvest date on the nitrogen (N), phosphorus (P), calcium (Ca), and magnesium (Mg) plant tissue concentrations. Only for Ca leaf concentrations the effect of infection status was not influenced by harvest date or nutrient element supply treatment and Ca concentration was higher in E‐ than in E+ plants. Differences between E+ and E‐ plants in P concentration were significant at the beginning of the experiment, and for N and Mg were observed at the end of the experiment (16 to 18 weeks). Endophyte‐infected plants had higher stem N and leaf Mg concentrations in the high nutrient element supply, but significantly lower concentrations at the low nutrient element supply treatment. Phosphorus concentration in leaf and aboveground plant tissue was significantly higher in E‐ than in E+ plants at the high nutrient element fertility treatment at week 12, but in the low fertility treatment differences were not significant. Differences in potassium (K), iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) concentration between infected and non‐infected plants were not statistically significant. Our results suggest that endophyte infection of tall fescue appears to increase the content of nutrient elements related to protein synthesis processes (N and Mg).

Uptake and utilization of atmospheric ammonia in three native Poaceae species: leaf conductances, composition of apoplastic solution and interactions with root nitrogen supply

The physiological potential for acquisition of atmospheric ammonia (NH3) was investigated in three European meadow grasses (Arrhenatherum elatius, Bromus erectus and Brachypodium pinnatum) competing in chalk grasslands. Experiments were carried out with plants cultivated for about three months on a soil–sand mixture at high root nitrogen supply or in nutrient solutions at low root nitrogen supply. Two different root nitrogen regimes were applied to the solution‐grown plants: 130 μmol NO3 plant−1 wk−1 (approx. 50 kg nitrogen ha−1 in three months); or 130 μmol NO3− plus 130 μmol NH4+ plant−1 wk−1. Each regime was combined with two levels of NH3 fumigation (0 and 70 nmol mol−1 air for 24 d). Uptake of gaseous NH3 in the shoots was investigated under controlled environmental conditions including NH3 concentrations ranging from 0 to 30 nmol mol−1 air. Concurrently, photosynthesis, glutamine synthetase activity, nitrogen allocation, biomass allocation and apoplastic cation composition were measured. For A. elatius, the influence of photorespiration on NH3 acquisition was also assessed. Independently of plant nitrogen status, ammonia compensation points in A. elatius and B. erectus plants were &lt;0.5 nmol mol−1. The total leaf conductance to NH3 absorption remained constant at increasing NH3 concentrations, showing that the capacity for assimilation was unaltered. Whereas internal factors in the leaves did not cause differences in the potential for NH3 acquisition between the species, other factors of NH3 acquisition were quite different: B. erectus had higher stomatal conductance and, thus, higher NH3 uptake rates per unit leaf area compared to A. elatius and B. pinnatum; higher stomatal conductances of B. erectus were to a large extent offset by a lower leaf area per plant, resulting from a lower growth rate and thicker leaves than in the two other species. The rate of photorespiration in Arrhenatherum constituted at least 15% of the net photosynthetic rate. Surprisingly, suppression of photorespiration indicated that NH3 uptake was supported by photorespiration. Bromus responded to fumigation with 70 nmol NH3 mol−1 air for 24 d by lowering the root∶shoot ratio and increasing the nitrogen concentration in the stem dry matter. The total leaf conductance to NH3 uptake decreased in all three species upon exposure to NH3, while the stomatal conductance was unaffected. The NH3 exposure caused lower apoplastic concentrations of H+, Mg2+ and Ca2+ in A. elatius and B. erectus.

Responses of elephantgrass to nutrient solution ph levels

Seedlings of elephantgrass (Pennisetumpurpureum, Schum.), cvs. Vruckwona and Napier, were grown in aerated nutrient solution and exposed to pH levels of 4.0, 5.0, 6.0, or 7.0. After 30 days under controlled conditions, the effects on growth were evaluated. Plants exposed to pH 5.0, as compared to those under pH 4.0, showed increases in total leaf area, plant height, number of leaves (NL), and leaf, root, and stem fresh weight. No significant differences were found in stubble fresh weight, maximum individual leaf area, leaf area ratio (LAR), leaf area:plant height ratio, and leaf, root, stem, and stubble dry weight and dry matter percentage. Seedlings exposed to pH 4.0, as compared to those under pH 5.0, exhibited higher leaf:stem ratio on a fresh weight basis (FWR) and a tendency for higher leaf :stem ratio on a dry matter basis (DWR). Cultivar Vruckwona yielded superior results than Napier for most studied parameters, except for NL, LAR, and DWR (in which there were no significant differences) and for stubble length and FWR (in which Napier performed better). The results suggest that reductions below 5.0 in the nutrient solution pH cause growth inhibition, affecting root, stem, and leaf FW to a greater extent. The magnitude of such effects varies among contrasting cultivars. In turn, pH increases above 5.0 induce no significant growth reduction or promotion.

Some factors affecting white stem borer Scirpophaga innotata (Walker) (Lepidoptera: Pyralidae) injury to rice

The amount of injury to rice caused by white stem borer Scirpophaga innotata depends on cultivar, and stage of plant and insect development, as well as insect abundance. Of the cultivars tested, IR64, IR42, Cisadane and Ketan, IR64 were the most susceptible and Ketan the least susceptible to feeding damage. Third and fourth instars consumed more stem dry matter than other stages, although yield reduction depended on the number of tillers injured. On the wider stemmed Ketan, fewer tillers were injured than the narrower IR64. Larvae are more likely to move among tillers in the third instar stage, which tends to coincide with maximum tillering and may result in more tillers injured and in yield reduction. Later instar larvae burrow downwards to the internode where they pupate. Larvae appear to move less among tillers in ‘resistant’ cultivars. Management strategies should target this pest at third instar and when its abundance in the field warrants control. Fewer than 10% of the neonates establish successfully on stems, and this mortality needs to be taken into account when deciding on control, as does the ability of rice plants to compensate for injury.

Uptake and Partitioning of Nitrogen by Maize Infected withStriga hermonthica

The uptake and partitioning of nitrogen (N) by maize infected with the parasitic angiosperm,Striga hermonthicawas investigated in sand culture in a glasshouse. The purpose was to determine the effect ofStrigaon N uptake and partitioning in maize. Maize was grown at 22, 66 and 133 mg N per plant and sampled five times. There was no significantStriga×N interaction in any measured response. Leaf dry matter ofStriga-infected maize, averaged over all N treatments, was 92% that of uninfected maize at the four-leaf stage but by the 18-leaf stage it had decreased to 58%. Similarly, stem dry matter of infected maize which was 91% that of uninfected maize at the four-leaf stage was only 42% at the 18-leaf stage. Root dry matter was similar for infected and uninfected maize. N concentration in the leaf, stem and root declined asymptotically from the first to the last sampling date for both infected and uninfected maize. The asymptotic value of N concentration inStriga-infected maize was 16% greater in the leaf, 55% in the stem, and 21% in the root than in uninfected maize. The concentration of N inStrigawas higher than in maize at the 16- and 18-leaf stages. Uptake of N was similar for infected and uninfected plants at the four–eight leaf stage but at the eight–12 leaf stage, N uptake by infected maize was 52% that of uninfected maize. However, the proportion of total plant nitrogen partitioned to the root was greater (P<0.001) forStriga-infected maize. These results showed that the extent to whichS. hermonthicareduced maize growth and N uptake, but increased the proportion of N partitioned to the roots, did not depend on the rate of N fertilizer applied.

Determination of a Critical Nitrogen Dilution Curve for Winter Oilseed Rape

Abstract Several controlled environmental and field experiments were carried out to define the critical nitrogen dilution curve for winter oilseed rape, cultivar Goeland. This curve is described by the following power equation:N=4.48 W-0.25,whereNis the total nitrogen concentration in the shoot biomass andWthe shoot biomass. This curve has been validated over the range of shoot dry matter of 0.88 to 6.3 t ha-1. For lower shoot biomasses this equation overestimated the critical nitrogen concentration; we propose a constant value of 4.63 (Nis expressed in reduced N, which is a more stable N fraction in the shoot at these stages of development). These results have been validated in several pedoclimatic conditions in France on a single variety in 1994 and 1995. The higher position of this curve relative to the C3species reference curve (Greenwoodet al.,Annals of Botany67: 181–190, 1990) can be explained by the experimental conditions obtained by Greenwoodet al. (1990); therefore, all their rape data are rather close to the critical curve that we propose. The differences found between wheat and winter oilseed rape critical N dilution curves correspond to their respective leaf:stem dry matter ratio and the specific leaf loss phenomenon occuring in rape. Winter oilseed rape has a higher capacity of N accumulation in its shoot than wheat for the same aerial dry matter. The proportion of nitrate in shoots rises with the nitrogen nutrition index (N.N.I.) and is more important for rapeseed than for wheat for the same N.N.I. This difference is especially high at the beginning of flowering when the shade provided by the canopy of rapeseed flowers decreases nitrate reductase activity.

Effect of late nitrogen application on growth and nitrogen balance of two cultivars of water-stressed grain sorghum

With development of water stress during grain filling, sorghum crops lose green leaves, and nitrogen (N) is remobilised from the leaves to grain. Supplementary N application just before anthesis may reduce leaf senescence, contributing to dry matter production during grain filling and, hence, grain yield. This hypothesis was tested using 2 sorghum hybrids which were known to differ in capacity for osmotic adjustment and the ability to retain green leaves under water stress, in a rainout shelter experiment in south-east Queensland. When N was applied at depth (&gt;70 cm) where water was available, all N applied was apparently taken up by the plants, resulting in reduced leaf senescence, particularly for leaves in the middle layer. Remobilisation of N from leaf to grain during grain filling was reduced by the supplementary N application. Both stem and leaf were the source of remobilised N which contributed about 65% of the total grain N without supplementary N application, this being reduced to about 30% with N application The hybrid with known high osmotic adjustment had greater total above-ground dry matter, particularly stem dry matter, at anthesis than the other, providing more material for translocation to fill grains. It also maintained greater leaf area during early stages of grain filling. This hybrid produced significantly higher yield (465 v. 412 g/m2) only when supplementary N was applied. Without supplementary N application, their yields were similar at about 350 g/m2. It is concluded that provided N is taken up by the sorghum plants, late N application is effective in increasing grain yield under water-limiting conditions. Cultivars, however, differed in their responses to the application.

Preliminary evaluation of the suitability of Enterolobium cyclocarpum for use in intensive feed garden in southwestern Nigeria

The best method of establishment of Enterolobium cyclocarpum (enterolobium) and biomass yields and nutritive value under cutting were determined in three separate trials. Soaking in boiled water for 30 seconds gave the highest percent seed germination (76%) and most vigorous seedlings. Transplanted seedlings out-grew direct-seeded plants with 1.70 and 1.12 m, respectively, at six months after planting. Intra-row spacing did not significantly affect early growth of the plants. Cutting every 12 weeks gave the highest leaf (4.05 t/ha), stem (2.26 t/ha) and total (leaf + stem) dry matter yields. Cutting regimes did not significantly affect the crude protein and neutral detergent fibre content of the leaves which averaged 21.3 and 60.7%, respectively. This initial study suggests that enterolobium has a potential as a forage tree and should be further studied to understand its agronomy and feed value.

The effect of dwarfing genes on sorghum grain filling from remobilized stem reserves, under stress

Stem reserves are increasingly recognized as an important source for grain filling when current photosynthesis is inhibited by stress. However, information in this respect for sorghum is seriously lacking. This study was designed to test the hypothesis that tall (1-dwarf) sorghum has greater stem reserve storage than shorter (3-dwarf; ‘combine height’) sorghum and that under conditions of environmental stress during grain filling this storage becomes an important source for grain filling. Tall (SA1170) and short (SM 100) isogenic lines of milo sorghum ( Sorghum bicolor (L.) Moench.) were tested in the field for 3 years under 3 treatments: (a) full irrigation (control); (b) drought stress which intensified towards grain filling; and (c) chemical desiccation of the leaf canopy at 12 days after anthesis, which eliminated the main photosynthetic source during grain filling. Data were collected on grain dry matter, stem dry matter and stem water soluble carbohydrates (WSC) changes with time. The tall genotype was about 2 m and the short genotype was about 1 m tall, under non-stress conditions. It was found that grain weight per panicle was reduced by drought stress only in the short genotype. Both kernel number and kernel weight and their interaction were responsible for this reduction. Chemical desiccation was a more aggressive treatment than drought stress. It reduced kernel weight and grain weight per panicle much more in the short than in the tall genotype. Changes in stem dry matter reflected well the changes in stem WSC content. Maximum stem weight at the onset of grain filling and stem dry matter loss during grain filling were always greater in the tall than the short genotype. Stem weight loss was markedly promoted by drought and chemical desiccation only in the tall genotype or in the short genotype only in a year when it developed heavy stems. Stem weight loss as percent of grain weight per panicle under drought and chemical desiccation was always greater in the tall than in the short genotype. Since stem weight loss was promoted by stress, it could not have been fully accounted for by maintenance respiration. Irrespective of year, treatment and genotype, plants with greater stem weight at the onset of grain filling lost more reserves from the stems during grain filling ( r = 0.89, p < 0.0001; n = 18). Consequently, stem weight loss as percent of grain weight per panicle increased with larger stem weight ( r = 0.73, p = 0.0006; n = 18). It is concluded that large stem reserve storage at the onset of grain filling ascribe stable grain filling under any stress which depresses the photosynthetic source during grain filling.

The potential of hemp (Cannabis sativa L.) for sustainable fibre production: a crop physiological appraisal

Summary.Hemp (Cannabis sativa L.) fibre can be used as a raw material for paper and textile production. A comprehensive research programme in the Netherlands has concluded that fibre hemp is a potentially profitable crop, having the right profile to fit into sustainable farming systems. This paper presents an appraisal of the crop physiological characteristics and the agronomic potential of hemp. Parameter values of basic crop physiological characteristics such as light interception potential, radiation use efficiency and dry matter partitioning coefficients are given. The effect of crop management decisions such as cultivar choice, sowing date, plant density, and harvest date on the value of these parameters is discussed. A simple crop growth model was used to assess the yield potential of hemp for the climate of the Netherlands. Calculations made for a non‐stressed late‐flowering hemp crop sown on 15 April and harvested on 15 September give a stem dry matter yield of 17.1 t ha‐1. The effects of advancing or delaying sowing or harvest date on stem yield were calculated. Crop physiological characteristics of hemp are compared to those of kenaf (Hibiscus cannabinus L.). Radiation use efficiency and dry matter partitioning coefficients of the two crops are similar. Base temperatures for development and growth are lower in hemp than in kenaf. In a temperate climate with cool springs, canopy establishment will be more rapid in hemp than in kenaf. Hemp seems an excellent candidate to fill the niche for an annual fibre crop in a temperate climate.

Nitrogen and potassium nutrition of Australian waxflowers grown in siliceous sands. 1. Stem growth and yield responses

The effects of nitrogen (N) and potassium (K) on stem growth and yield responses of Australian waxflowers were investigated. Experiments were conducted in commercial plantings at 3 sites in South Australia. Plantings of Chamelaucium uncinatum cvv. Alba (2 sites) and Purple Pride (1 site) and a Chamelaucium hybrid (C. floriferum x C. uncinatum), known locally as Walpole wax (1 site), were 3-5 years old when the study began in 1990. Nitrogen and K were applied at rates up to 160 g N and 80 g K/plant.year. Application of N significantly (P&lt;0.05) increased stem growth, with the magnitude varying considerably between sites and years. Increasing the rate of applied N from 0 to 80 or 160 g/plant.year increased mean tip-growth of flowering stems of cv. Alba by 47.7% at site 1 and 137.1% at site 3, and of Walpole wax by 144.2% at site 2. In contrast, the effect on cv. Purple Pride was minimal. Tip-growth also varied significantly (P&lt;0.05) between sites. Applied K did not significantly affect stem growth at any site. Application of N significantly (P&lt;0.05) increased the yield of 41-70 and &gt;70 cm stems, and total stem yield at all sites with variation between years and cultivars. For example at site 2 increasing the applied N rate from 0 to 80 or 160 g/plant .year increased total stem yield by 13.9, 176.2 and 77.6% in 1991, 1992 and 1993, respectively. In contrast, the effect of applying K was inconsistent. Application of N significantly increased the weight of prunings at all sites and yield of prunings also varied between years. Applied K significantly affected the yield of prunings at site 3, where application of 80 compared with 0 g1plant.year decreased the yield by 17.9%. For all sites, the mean ratios between total stem weight and total biomass harvested were in the range 0.68-0.82. The effect of applied N was only significant at site 3, where the ratio decreased from 0.76 to 0.57 when the rate of applied N increased from 0 to 160 g/plant.year. The effect of K was not significant at any site. At sites 1 and 2, and for cv. Alba at site 3, application of 80 or 160 g N1plant.year decreased mean stem dry matter by 8.0, 9.3 and 11.0%, respectively. Stem dry matter content also varied significantly between years at all sites. The effect of applied K was only significant at site 3, where application of 80 g1plant.year reduced dry matter content by 5.3% compared with 34.2% for the nil rate. Based on data for all sites, stem fractionation showed that dry matter yields (as a percentage of total stem dry weight), were in the order, woody tissue (3 15-49.9%) &gt; leaves (22.1-29.2%) &gt; flowers (15.9-25.8%) &gt; tip-growth (5.0-21.9%). The effect of applied K on the yield of the different stem parts was only significant (P&lt;0.05) at site 1, where in 1991 yield of the tip-growth fraction decreased. We conclude that to develop effective N fertiliser strategies for waxflowers requires knowledge of (i) soil type, in particular residual N fertility; (ii) annual vegetative growth cycle (i.e. periods of growth flushing); (iii) harvest period; and (iv) flowering time. For cultivars or hybrids harvested when vegetative growth is negligible (e.g. winter) N nutrition can be optimised, while for those harvested during periods of vegetative flushing (e.g. September-November) lower rates of N should be applied to ensure tip-growth is not excessive. Although yield responses to applied K were inconsistent, we recommend 20 g K/plant.year to ensure that productivity is maintained over the 5-10 years flowering stems can be harvested from commercial plantings.

The Comparison of Growth and Development Proporties, Dry Matter Accumulation and Quality Characters of Spring and Winter Oilseed Rape (Brassica napus L.) Cultivars Grown as Winter-Sown

In order to compare the growth and development properties, dry matter accumulation (DMA) and quality characters of oilseed rape winter cultivars (Quinta, Bienvenue, Cobra and NPZ) and spring cultivars (Loros, Proto and Semu 209/82 RH) grown as winter-sown crop under Antalya region, it was carried out a series of experiments in 1991-1993. Excessive vernalization requirements of some winter cultivars resulted in delay at their rosette stage and failure of the plants to initiate flowering due to inefficient cooling in 1991-92. Spring cultivars required none vernalization elongated their mains stems before and faster than winter cultivars with the beginning of high temperatures and long days after cool winter days. It was found that the total dry matter (DM) production and DMA in the parts of plants were different between spring and winter cultivars. Spring cultivar Loros accumulated less leaf and root DM in the rosette stage, but more stem and pod DM in the flowering and pod filling stages. Loros contained less glucosinolate with 11.9 µmol/g and more oil with 57.1 % than winter cultivars. But Winter cultivars contained more protein, oleic and linoleic acids than Loros.

Efficiency of Nitrogen Assimilation in Tomato Seedlings as Affected by Nitrogen Regime and Photoperiod

Excessive nitrogen can be detrimental to transplant quality when supplied during the period of suboptimal photoperiod conditions. This investigation was made to determine the relationship between nitrogen and photoperiod on the growth rate of the transplants. The growth analysis included the determination of the net assimilation rate (NAR) and the nitrogen productivity (NP). `Camone' tomato (Lycopersicon esculentum Mill.) seedlings were grown in the greenhouse under two photoperiods 8 and 12 h) at a constant light intensity and fertilized with three different N concentrations (8, 15, and 30 mmol·liter–1) applied four times. Longer photoperiods enhanced plant growth by increasing the internode, LAR, SLA, and SWR. Root fresh weight, dry weight, stem dry matter, NAR, and RWR were minimal when 30 mmol·liter–1 N concentration was supplied, while LAR and SLA were at their maximum level. The interaction between N and photoperiod was significant. Increasing N supply during an 8-h photoperiod decreased growth. During a 12-h photoperiod, 15 mmol·liter–1 was the optimum N concentration for fresh growth and 8 mmol·liter–1 for shoot dry growth. The RGR had the lowest value, with 30 mmol·liter–1 N and 8-h photoperiod. PNC was highest when plants received 30 mmol·liter–1 N during an 8-h photoperiod, and when the plants received 15 and 30 mmol·liter–1 N during the 8-h photoperiod. LNC doubled in plants fertilized with 30 mmol·liter–1 N compared to those with 8 mmol·liter–1 when grown under a 12-h photoperiod. The NP was at the maximum in plants fertilized with 8 mmol·liter–1 N at the 12-h photoperiod. The lowest NP values occurred when plants were fertilized with 30 mmol·liter–1 N. When photoperiod is a limiting factor in growing seedlings, N supply must be limited to optimize the efficiency of its utilization by the plant.