DM Accumulation Research Articles

Contrasting physiological responses to high salinity between two varieties of corn ‘Lluteño’ (salt tolerant) and ‘Jubilee’ (salt sensitive)

'Lluteno' is the only one corn capable to prosper in the Valley of Lluta under saline conditions (EC = 9.1 dS m-1). This cultivar has been little studied and there is no current information about its growth and about the possible mechanisms involved in its tolerance to salts. The aim of this research was to compare the growth of young plants of corn ( Zea mays L.) 'Lluteno' to that of the bred 'Jubilee', both grown under different salt concentrations, to characterize the absorption and distribution of Na+ and other nutrients in the plant and to evaluate the effect of the saline conditions in the osmotic adjustment in both cultivars. The plants of 21 d old were subjected for 15 d to two saline treatments: 50 and 100 mM NaCl. The accumulation of DM was reduced from 5.12 to 1.80 g plant-1 in 'Jubilee' and 5.53 to 4.12 g plant-1 in 'Lluteno' (P ≤ 0.05). 'Lluteno' showed to be more tolerant to salt stress that 'Jubilee' by greatest accumulation of biomass under saline conditions, it was associated with a lower accumulation of Na+, steadiness of K+ and Ca2+ content and accumulation of osmolytes in leaves. The latter affecting positively the maintenance of relative water content and the osmotic adjustment of this cultivar in the leaves.

Water use efficiency, transpiration and net CO 2 exchange of four alfalfa genotypes submitted to progressive drought and subsequent recovery

The predicted worldwide increase in arid areas and water stress episodes will strongly affect crop production. Plants have developed a wide diversity of physiological mechanisms for drought tolerance. A decline in photosynthesis and thus yield production is a common response to drought, as are increases in the water use efficiency of photosynthesis (WUE ph) and productivity (WUE p). The aim of our study was to determine the physiological effects (especially WUE ph and WUE p) of progressive drought and subsequent recovery in three cultivars adapted to a Mediterranean climate [Tafilalet (TA), Tierra de Campos (TC), and Moapa (MO)], and another representative from an oceanic climate (Europe (EU)). The accuracy of the relationships between WUE ph or WUE p and carbon isotope discrimination (Δ 13C) in shoots was also investigated as a function of water stress intensity. Mild drought (7 days of water withholding) decreased the net CO 2 exchange ( A), leaf conductance to water (g) and transpiration in EU leading to an increased WUE ph. Δ 13C was correlated with WUE p but not with WUE ph, probably due to a late decrease in g. After moderate drought (14 days), A and g decreased in all cultivars, increasing WUE ph. In this period WUE p also increased. Both WUE parameters were correlated with Δ 13C, which may indicate that the g value at the end of moderate water stress was representative of the growing period. After 21 days, TA was the most productive cultivar but under severe drought conditions there was no difference in DM accumulation among cultivars. After the recovery period, leaf area was increased but not total DM, showing that leaves were the most responsive organs to rewatering. Severe water stress did not decrease WUE ph or WUE p, and Δ 13C did not increase after recovery. This absence of a response to severe drought may indicate significant effects on the photosynthetic apparatus after 21 days of withholding water. As for mild drought, WUE p but not WUE ph was correlated with Δ 13C, supporting the view that WUE p is a more integrative parameter than WUE ph.

Effect of rate and method of phosphorus application on the growth and development of 'Pasja' crops

'Pasja' (Brassica campestris x napus) was grown at Lincoln in 2008, with banded or broadcast phosphorus (P) fertiliser applied at 0, 20, 40 or 60 kg/ha at establishment on a Templeton silt loam soil of moderate fertility (Olsen P of 9-17 mg/ kg range for individual plots). Keywords: Brassica campestris, critical leaf area index, DM accumulation, leaf area index, leaf to stem ratio, solar radiation

Seasonal Biomass and Nitrogen Accumulation of Rosa ‘Mariandel®’ Grown in Compost Amended Peat at Different Fertilization Rates

Abstract The growth and nitrogen (N) uptake of Rosa ‘Mariandel®’ were evaluated at four fertilization rates: 0, 0.4, 0.8 and 1.2 g N/liter (0, 0.016, 0.032 and 0.048 oz/qt). Plants were harvested at 6-week intervals. New shoots in all treatments retained the highest relative dry weight percentage, apparently at the expense of root. The total N concentration, content, and uptake at 12 and 18 weeks, but not at 6 weeks, after potting were significantly (r2 > 0.59; P = 0.0005) affected by rates of fertilization. Although DM in the old shoots of all treatments slightly increased over the first 6 weeks, the corresponding N content decreased due to translocation. Except in old shoots, a significant linear trend occurred between DM accumulation and N content but not with N concentration (at least up to 12 weeks). However, N concentration in most plant parts was significantly (P < 0.05) correlated with the respective N content. Excluding N released from the substrate, plants in 0.4, 0.8 and 1.2 g N/liter treated pots received 80, 126 and 182 mg (0.003, 0.004 and 0.006 oz) N per week, respectively, as used Osmocote (15N–4P–7.5K–1.8Mg) showed a linear (r2 > 0.99) N-releasing rate. The corresponding total mineralized N in each control pot was 96 mg (0.003 oz) and 140 mg (0.005 oz) over the first and the second 6-week interval. Overall, ‘Mariandel®’ grown in 0.8 and 1.2 g N/liter treated pots had the highest mean N concentration and content respectively.

Immunocytochemical studies on the distribution pattern of daunomycin in rat gastrointestinal tract

The cancer drug daunomycin is used in treatment of leukemia but possesses severe side effects that involve the gastrointestinal tract. We therefore used a newly developed immunocytochemical procedure to determine the distribution of DM in the gastrointestinal tracts of rats after i.v. injection. Two hours after injection, DM was diffusely distributed in nuclei and most parts of the cytoplasm of intestinal epithelial cells. The cytoplasmic immunoreactivity for DM was most pronounced in small granules of the apical cytoplasm. Sixteen hours after injection, DM immunostaining was by and large absent in the villous epithelium but persisted in the intestinal crypts. In addition, staining was also detected in endothelial cells, scattered cells of the lamina propria and in smooth muscle cells. After 5 days, only little staining for DM remained. Similar findings were made in the colon. In the gastric mucosa, DM accumulation persisted at 16 h in some glandular cells but was lost from the surface epithelium. No staining was detected in saline-injected control rats. The distribution of DM accumulation correlated partially with the distribution of apoptotic cells as detected by the TUNEL procedure. Our results pinpoint that DM may exert prolonged effects on glandular and regenerative cells of the gastrointestinal tract-an observation that may explain the gastrointestinal toxicity of the drug. It seems possible that DM accumulation in surface epithelial cells is rapidly cleared through drug transporters.

Produção e qualidade da forragem de capim-marandu fertiirrigada com dejetos líquidos de suínos

Esta pesquisa foi realizada com o objetivo de avaliar os efeitos da fertilização com dejetos líquidos de suínos (DLS) nas características agronômicas e bromatológicas da forragem de capim-marandu. Foram avaliados a produtividade de MS, o perfilhamento, o percentual de MS, PB, FDN e FDA e a digestibilidade in vitro da MS (DIVMS). Adotou-se o delineamento em blocos casualizados, com nove tratamentos (adubações) e quatro repetições. Os tratamentos são descritos a seguir: T1 - uso de calcário; T2 - adubação com 100, 40 e 60 kg/ha de N P K; T3 - 180 m³ de DLS/ha 1x/ano; T4 - 180 m³ de DLS/ha 2x/ano); T5 - 180 m³ de DLS/ha 3x/ano; T6 - 180 m³ de DLS/ha 4x/ano; T7 - 180 m³ de DLS/ha 5x/ano; T8 - 180 m³ de DLS/ha 1x/ano (in natura); T9 (testemunha) - fermentação do DLS utilizado nos tratamentos 1, 2, 8 e 9 por, no mínimo, 45 dias. As médias foram comparadas pelo teste Scott-Knott. Na calagem, utilizou-se alcário dolomítico na proporção de 3 t/ha e, na adubação química, 100, 40 e 60 kg/ha de N, P2O5 e K2O nas formas de sulfato de amônia supersimples e cloreto de potássio. Os cortes foram realizados a cada 45 dias. O número de perfilhos/m², a produtividade de MS e a qualidade da forrageira foram maiores com a utilização de DLS em dose única nos primeiros cortes. As forrageiras dos tratamentos 3, 4, 8 e 9 apresentaram maiores teores de PB nos primeiros cortes, com médias de 9,6 a 13,7%. Os maiores teores de FDN foram obtidos no segundo corte (médias de 61,4 a 68,6%) e os menores de FDA foram encontrados com DLS 2x/ano e 5x/ano no primeiro corte (médias de 21,2 a 23,4%). Os tratamentos 3, 4 e 8 proporcionaram os maiores coeficientes de DIVMS no primeiro corte, com médias de 69,0 a 71,8%.

Suplementação energética na recria de fêmeas de corte em pastagem cultivada de inverno: dinâmica da pastagem

Foi avaliada a dinâmica da pastagem de aveia preta (Avena strigosa Schreb) mais azevém (Lolium multiflorum Lam) utilizada por novilhas de corte submetidas a diferentes níveis de suplemento durante o período de pastejo. Os tratamentos foram: 'Sem Suplemento'- animais em pastagem de aveia mais azevém; 'Crescente' - animais em pastagem de aveia mais azevém, recebendo níveis crescentes de suplemento (0,3; 0,6; 0,9; 1,2 a 1,5% do peso vivo [PV]) durante o ciclo da pastagem; 'Fixo' - animais em pastagem de aveia mais azevém, recebendo 0,9% do PV de suplemento durante todo o ciclo da pastagem; e 'Decrescente' - animais em pastagem de aveia mais azevém, recebendo níveis decrescentes de suplemento (1,5; 1,2; 0,9; 0,6 a 0,3% do PV) durante o ciclo da pastagem. O suplemento utilizado foi farelo de trigo. Foram avaliadas a massa de forragem, taxa de acúmulo diário de MS, oferta de forragem, oferta de lâminas foliares verdes, massa de forragem verde e relação folha:colmo. Na composição botânica da pastagem foram avaliados os percentuais dos componentes folha de aveia, colmo de aveia, folha de azevém, colmo de azevém e material morto na MF. O valor nutritivo da forragem aparentemente consumida pelos animais foi avaliado com base nos teores de proteína bruta e na digestibilidade in vitro da matéria orgânica, nutrientes digestíveis totais e fibra em detergente neutro. As variáveis estudadas não foram afetadas pela suplementação ou pela variação no nível de suplemento. O ciclo da pastagem interferiu nas variáveis estudadas.

Animal and Forage Production and Economics of Three Grazing Systems for Beef Cattle

A 3-yr study was conducted to evaluate animal performance, costs, and returns for three grazing systems: 1) or- chardgrass/bluegrass; 2) orchardgrass/ bluegrass plus annual plants including sudangrass, small grains, rape, and corn stalks; and 3) orchardgrass/bluegrass, stockpiled fescue, and alfalfa-grass combinations. Fifteen cow-calf pairs contributed to a constant stocking rate within each system at each of two locations. Pastures were subdivided to provide grazing for 3.5 d and sampled pre- and postgrazing. Ungrazed forage mass was harvested as high-moisture baleage. Harvested, fed, and grazed DM masses were measured, and costs and returns were determined. Animal performance was not different across systems or forage varieties (P>0.05); however, calves tended to have less preweaning BW gain (P<0.08) while grazing System 3 (1.22, 1.21, and 1.14 kg/d for Systems 1, 2, and 3, respectively), which contributed to less weaning weight per cow exposed. Pregnancy rate and body condition scores for cows at weaning did not differ across systems. Grazed DM, hay production, and total DM accumulation were not different across systems. System 1 had the greatest net value per land unit ($371.60/ha), but was more sensitive to rainfall; 46% of the net returns were from hay. Alfalfa-grass combinations, corn stalks, and stockpiled fescue components had less annual cost, and System 2 had the least net returns because of tillage costs. Orchardgrass/bluegrass pastures had a greater net return compared with other systems, but DM production is highly dependent on rainfall and a greater portion of return from hay production. Functional grazing systems are available to farmers in the mid Atlantic region.

Morfogênese e acúmulo de forragem em pastagem de Cynodon dactylon cv. coastcross em diferentes estações de crescimento

O experimento foi realizado para se estimar as características morfogênicas e estruturais e a taxa de acúmulo de matéria seca (MS) de lâminas foliares em uma pastagem de Cynodon dactylon cv. coastcross, manejada em sistema de lotação rotacionada com vacas em lactação. As avaliações foram realizadas na primavera (outubro-novembro), no verão (fevereiro-março) e no outono (maio-junho). O estudo foi conduzido em delineamento de casualização completa, com seis repetições. Durante o período de descanso do piquete, os perfilhos do capim foram identificados para observações e registros de alongamento, aparecimento e senescência foliares. Foram contados perfilhos em área de 0,09 m², para estimativa da densidade populacional. A taxa de acúmulo líquido de MS de lâminas foliares/área foi obtida multiplicando-se o acúmulo de MS/perfilho pelo número de perfilhos/área. A taxa de alongamento foliar foi mais alta no verão, enquanto a taxa de aparecimento foliar e o número de folhas/perfilho foram mais elevados na primavera. O número de perfilhos não variou com a estação, apresentando valor médio de 2.770/m². A taxa de senescência foi, em média, de 2,44 mm/dia na primavera, não havendo senescência de folhas durante o verão e o outono. A taxa de acúmulo de MS de lâminas foliares foi mais alta no verão e apresentou estreita relação com a taxa de alongamento e com o tamanho da folha. O uso da taxa de alongamento foliar e da densidade de perfilhos para obtenção das taxas de acúmulo de MS de lâminas foliares/ha superestimou os valores.

Recria de bezerros em pastagem de aveia e azevém utilizando suplementação energética com níveis de promotor de crescimento

O presente trabalho teve como objetivo avaliar a produção animal em pastagem de aveia (Avena strigosa Schreb) e azevém (Lolium multiflorum Lam.), recebendo ou não suplementação, com e sem promotor de crescimento. O experimento foi conduzido no Setor de Bovinocultura de Leite do Departamento de Zootecnia da UFSM, no período de abril a setembro de 2003. Os animais utilizados foram bezerros machos desaleitados, da raça Holandês com idade média inicial de 3 meses e peso médio inicial de 88,7kg. Estes animais foram submetidos a pastejo contínuo com lotação fixa (carga média de 1.479kg de Peso Vivo por hectare (PV ha-1)) em pastagem de aveia e azevém recebendo ou não suplementação, com e sem um promotor de crescimento natural à base de óleos essenciais extraídos de plantas. Os tratamentos foram: S-0% = pastagem sem suplementação; S-1% = pastagem + 1% do peso vivo (PV) em matéria seca (MS) do suplemento ao dia; S-1% PC250 = pastagem + 1% do PV em MS do suplemento ao dia (com 250g de promotor de crescimento por tonelada de suplemento); S-1% PC500 = pastagem + 1% do PV em MS do suplemento ao dia (com 500g de promotor de crescimento por tonelada de suplemento). O delineamento experimental utilizado foi o de um quadrado latino 4x4, com duas repetições. As medidas dos animais e seu ganho médio diário (GMD), a massa de forragem (MF), altura da pastagem (ALT), taxa de acúmulo da pastagem (TAMS), taxa de desaparecimento de matéria seca (TDMS) e valor nutritivo da pastagem foram avaliadas. O GMD médio foi de 622g animal-1dia-1 para os animais suplementados e 294,5g animal-1dia-1para os não suplementados (P&lt;0,05). Os valores médios de massa de forragem (943,9 kg ha-1,MS), taxa de acúmulo (142,7kg ha-1 dia-1, MS) e taxa de desaparecimento de MS (133,2kg ha-1 dia-1, MS) não foram influenciados pelos tratamentos (P&gt;0,05). As diferenças de MF total são conseqüência da taxa de desaparecimento, já que as taxas de acúmulo de matéria seca foram semelhantes. O promotor de crescimento não afetou o desempenho e o desenvolvimento dos animais.

Acúmulo de forragem e eficiência de utilização do Nitrogênio em pastagens de Panicum maximum Jacq. (Acesso BRA-006998) adubadas com Nitrogênio

The work was carried out at Iapar in Paranavaí, state of Paraná, to evaluate the effect of nitrogen fertilization on access of BRA-006998, from 10/15/1998 to 05/03/1999. Four doses of N (0; 150; 300; and 450kg/ha/year) were applied to the pastures managed according to a rotational grazing. A randomized block design was used with split-plots, with N-doses studied in the plots and the GCs in the split-plots. The DM accumulation rate presented maximum value of 73.9; 96.2; 150.3; 189.6; and 129.9kg/ha/day (424; 438; 397; 385; 414kg N/ha/year, respectively) in the GCs 1, 2, 3, 4 and 5, respectively. The efficiency of N utilization in DM production did not differ between the treatments of 150 and 300kg N/ha/year, where the efficiency obtained with 150kg N/ha/year is higher than that obtained with 450kg N/ha/year.

Digestive processes of dairy cows fed silages harvested at four stages of grass maturity.

The objective of this experiment was to quantify ruminal digestive processes that could help to identify factors limiting DMI when silages differing in grass maturity were fed to dairy cows. Four silages were harvested at 1-wk intervals from a primary growth of a timothy-meadow fescue sward, resulting in feeds with digestible OM content in DM (D-value) of 739, 730, 707, and 639 g/kg in the order of succeeding harvest date. Four ruminally cannulated dairy cows were given ad libitum access to these silages supplemented with 7 kg concentrate per day in a 4 x 4 Latin square design. Rumen function was clearly affected by decreasing digestibility of silage fed. Passage rate of digestible NDF (DNDF) and indigestible NDF (INDF) increased, but it could not prevent the accumulation of DM, NDF, DNDF, and INDF into the rumen when silages of progressing grass maturity were fed. The greatest proportional increases in rumen pool were found in INDF and in medium particles (separated by wet sieving and measuring 315 to 2,500 microm). The passage of medium INDF particles decreased (P < 0.01) linearly (from 0.0365/h to 0.0281/h) with increasing maturity of grass ensiled, and it was slower than passage of small (80 to 315 microm) particles (on average 0.0524/h). Particle size reduction of large INDF particles to medium INDF particles was slower (P < 0.001) in the early cut silages (0.0216/h to 0.0484/h) but reduction of medium INDF particles to small INDF particles was faster (P < 0.001) in early cut silages (0.0436 to 0.0305). Passage of medium size particles and(or) rate of medium particle breakdown to small particles were potential intake-constraining properties of low digestibility forages, whereas large particle reduction to medium particles seemed not to be limiting. The increased feed intake of the early-cut silages was accompanied by decreased rumen fill, suggesting that rumen fill was not at least solely responsible for feed intake control.

New Cropping Strategy to Reduce Chemical Fertilizer Application to Silage Corn Production Using Subterreanean Clover Reseeding.

This study was conducted to evaluate the effects of reseeding sub clover as a cover crop on silage corn growth, nitrogen accumulation, and the changes in soil nitrogen under different chemical nitrogen application levels. The cropping systems of sub clover reseeding based management and fallow treatment were compared to DM and N accumulation of silage corn at 0, 50, and 100kg N ha-1 application levels. The experiment was conducted at two sites, one where no-till corn was sown in June, and the other where conventional corn was sown in July. DM accumulation of corn in the fields of sub clover reseeding system was significantly higher than in the fields of fallow system at both sites. Based on this co-relationship, the amounts of nitrogen supplied by sub clover reseeding to no-till and conventional tilled corn estimated to be 108 and 88kg N ha-1, respectively. However, the evaluation of sub clover N supply in this experiment was obviously influenced by sub clover N that was also produced other years were obvious. So these results also suggested that there is some possibility to increase the soil total nitrogen in the field of sub clover reseeding system. However, the amount of sub clover N supply per year is still not clear, so additional research is needed.

Breeder Age Influences Embryogenesis in Broiler Hatching Eggs

The effects of dietary fat and broiler breeder age on egg and embryo characteristics during incubation were investigated. Breeders were fed diets containing no added fat or 3.0% added poultry fat (PF) for peak energy intakes of 430 and 467 kcal/hen day (pC/d), or 1.5% PF or 3.0% corn oil at 449 pC/d. Feeding of diets was initiated at 22 wk, and eggs were collected for incubation at 27 and 36 wk of age. Percentage incubational egg weight loss was determined between day of set and Days 6, 12, and 18. Percentage wet and dry embryo weights, embryo moisture content, and eggshell weights were determined at 6, 12, and 18 d of incubation. Percentage yolk sac weight and wet and dry liver weights and moisture content were determined on Days 12 and 18. Percentage gall bladder weight was determined on Day 18. There were no observed effects due to breeder diet. However, eggshell weight at Days 6, 12, and 18 was higher in 27-wk-old hens compared with 36-wk-old hens. Conversely, egg weight loss between Day 0 and Days 6, 12, and 18 and yolk sac weight across Days 12 and 18 of incubation were lower in eggs at 27 wk of age compared with 36 wk. At Day 18, dry embryo weight was higher and wet liver weight was lower at 27 wk compared with 36 wk. A slower rate of DM accumulation in embryos at Week 36 compared to Week 27 was associated with increased incubational water loss and decreased embryo moisture content, eggshell percentage, and yolk sac absorption rate. These data demonstrate that changes in eggshell characteristics with broiler breeder age can alone impact yolk uptake, growth, and body composition in subsequent embryos.

Kenaf Dry Matter Production, Chemical Composition, and In Situ Disappearance When Harvested at Different Intervals

Kenaf (Hibiscus cannabinus L.) is a tropical plant that has potential as a forage crop. However, data on the amount and quality of forage produced by kenaf is scarce. The objectives of this research were to determine 1) the DM yield, proportions of leaf and stalk, and chemical composition and 2) the in situ OM and N disappearance of kenaf harvested throughout the growing season. Kenaf (‘Everglades 41’) was planted in June of 1990, 1991, and 1993. The seeding rate was 5.6 kg/ha and 100kg of N /ha was applied shortly before or after planting. Harvesting began 40 d after planting (DAP) with additional harvests at 10-d (1991 and 1993) or 20-d (1990) intervals. Daily whole plant DM accumulation ranged from 12.6 to 17.2 g/m2. At 101 DAP, 726 to 974g of DM were harvested/m2. As kenaf matured, the proportion of the total plant DM represented in leaves decreased (P<0.01) from 68% at 40 DAP to 44% at 101 DAP. Leaf DM contained more (P<0.01) than twice the CP as stalk DM at all harvests. Delaying harvest decreased (P<0.01) whole plant CP concentration from 22% at 40 DP to 15% at 101 DAP, because the stalks made up a larger proportion of the total biomass. The OM in the leaves was twice as digestible (P<0.01) as the OM in the stalks (89.3 vs 44.8%). The N in the leaves was more (P<0.01) digestible than the N in the stalks (93.2 vs 61.5%). Kenaf can be grown during the summer season and harvested as high quality forage as early as 40 DAP. Whole plants harvested at 80 DAP produced from 426 to 729 g/m2 of DM and had a CP content of 14 to 19%. Harvesting later than 80 DAP will increase DM yield, but CP content and in situ OM and N disappearance will decrease.

Ontogenic Changes in Growth and Assimilate Distribution as Influenced by N Supply in Rapeseed‐mustard

Abstract Brassica juncea, cv. Pusa Bold, and Brassica campestris, cv. Pusa Kalyani, were raised under field conditions with varying levels of N fertilization, i.e. 0, 40, 80 and 120 kg N ha−1. Changes in dry matter accumulation in various plant parts as influenced by N supply were measured throughout the crop ontogeny. N supply up to 120 kg had an increasing effect on the growth of leaves, stem and pods during the entire period till maturity. Analysis on the assimilate distribution pattern revealed that 84–87% of the total was accumulated during the post‐flowering phase. Dry matter partitioning profile during the ontogeny indicated that about 72–83 % of the total DM was accumulated in the leaves, while 17–28 % in the stem, in the preflowering phase. This trend was found nearly opposite during the postflowering phase. At maturity, however, stem and pods accounted for nearly equal amounts of dry matter accumulation. Among the genotypes, Pusa Bold recorded significantly higher DM accumulation and seed yield over Pusa Kalyani which, on the other hand, exhibited a better assimilate‐partioning ability than the former. Nitrogen levels had a favourable effect on LAI, LAD and CGR in both genotypes. Highly significant correlations were obtained between seed yield vs. LAI, LAD and CGR. N fertilization up to 120 kg ha−1 was found beneficial in enhancing growth and yield of rapeseed‐mustard.

Phosphorus uptake by root systems: mathematical modelling in ecosys

The uptake of P by plant root systems is believed to be controlled by the concentration of soluble orthophosphate at the root surface. If a P transformation model in which this concentration is calculated were coupled to a root and mycorrhizal growth model in which this concentration is used to calculate P uptake, then it should be possible to simulate P uptake under different soil and climate conditions if soil properties relevant to the control of P concentration are known. To test this idea, models for the transformation and transport of inorganic and organic P were coupled to ones for root growth and nutrient uptake as part of the ecosys modelling program. Seasonal estimates of soluble P concentration, root growth and P uptake from the combined models were tested with data measured from barley under fertilized and unfertilized treatments in a long term P fertilizer experiment conducted on two different soils. In both soils the fertilizer treatment increased simulated and measured soluble P concentrations from 0.1-0.2 to 0.2-0.4 g m-3, annual P uptake from 0.6-0.7 to 1.2-1.4 g m-2, and annual DM accumulation from 400-500 to 700-800 g m-2. Increases in soluble P concentrations caused by fertilizer P were reproduced in the model from changes in the balance between the desorption and dissolution of solid P on one hand, and the uptake of P by root and mycorrhizal systems on the other. Increases in P uptake caused by fertilizer P were reproduced in the model from higher solution P concentrations, root uptake kinetics, and from functional equilibria for C and P exchange simulated among mycorrhizal, root and shoot components of the plant. There was a tendency in the model to overestimate P uptake later in the growing season in the unfertilized treatment which could be corrected if parameters for root uptake kinetics were reduced after anthesis. Because the model is constructed independently of data for P uptake, and avoids the use of site-specific parameters, it may provide a means of estimating uptake under different managements and climates from soils of known properties.

Effects of nitrogen on accumulation and partitioning of dry matter and nitrogen of vegetables. 2. Leek

Two greenhouse and 2 field trials were carried out on leeks cv. Albana with different N fertilizer rates and application dates. Observations included frequent measurements of DM and N accumulation in leaf blades, leaf sheaths and, if present, scapes. Both the amount of N applied and the time of application affected the total accumulation of DM and N in the plant. The relative partitioning rates of DM increase to the shaft were affected in such a way that the final harvest indices for DM (which ranged from 0.32 to 0.53) were significantly lower at higher N application rates. The final harvest indices for N (0.21-0.35) were not significantly affected by amount or timing of fertilizer applications. The total N concentrations of leaf blades and leaf sheaths decreased with increasing leaf age. Average nitrate N concentrations over all plant parts were always below 40%.

Dry matter accumulation and seed yield of dwarf autumn-sown white lupin (Lupinus albus L.)

DM accumulation and seed yield formation of the dwarf autumn-sown white lupin XA100 were compared with those of the tall cultivar Lunoble for 3 yr and at two plant densities to analyse to what extent the DM allocation to seed could be altered by dwarfism. At maturity, XA100 produced an average of 10.5 t ha−1 of above-ground DM, whereas Lunoble produced 12.3 t ha−1. Seed yield of XA100 (3.59 t ha−1) and Lunoble (3.36 t ha−1) were not significantly different, but the harvest index was 0.38 for XA100 and 0.32 for Lunoble. The reduction of the proportion of DM in XA100 stems was associated with an increase in the proportion of DM allocated to pods. The contribution of each pod order to total seed yield was different for XA100 and Lunoble, with XA100 producing more on the third and fourth branch orders. The low mainstem seed yield of XA100 was associated with late pod and seed abortion. XA100 mean seed weight was 0.287 g, and its seed protein concentration was 382 g kg−1, both of which were higher than for Lunoble. XA100 was not selected for its yield potential. However, no agronomic problem associated with dwarfism was detected in this experiment. Consequently, the characteristics of the dward lupin have to be considered for the breeding of autumn-sown white lupin. Key words: White lupin, dwarfism, growth, dry matter partitioning, seed yield, harvest index

Residual effects of irrigated soybean on the growth and yield of irrigated grain sorghum

Irrigated grain sorghum was cropped immediately following irrigated soybean, to establish whether there were any residual effects on sorghum from the previous management of soybean. Results of experiment 1 showed that, where soybean residues were incorporated, sorghum DM accumulation and grain yields were greatest where soybean had been least frequently irrigated (after about 240 mm cumulative open pan evaporation), and least where the soybean had been grown with saturated soil culture (SSC). Extractable mineral nitrogen (N) at sowing of the sorghum was also least following the SSC soybean and greatest following the least-frequently irrigated soybean. The subsequent availability of N during sorghum growth appeared greater where the soybean was more frequently irrigated, although the release occurred too late to influence grain yield. In experiments 2 and 3 residual effects of conventional irrigation of soybean after 60 mm evaporation were compared with those of SSC. Where soybean stubble was uniformly removed (experiment 2), no significant effects of previous irrigation were observed. Where soybean stubble was either removed or incorporated (experiment 3), sorghum yields were lower following the SSC soybean. The incorporation of soybean stubble delayed the release of soil N, although this was not reflected in lower sorghum yields. Taken together, the studies suggested that, for a sorghum crop following soybean, more N fertiliser will be needed at sowing where the soybean stubble is incorporated; where the soybean had been well-irrigated; and the sooner after soybean harvest the sorghum is sown. Conversely, there were indications that more N may be available late in the growth of the sorghum crop where soybean had been well irrigated.