The selection of pulses in Suriname

The consumption of pulses in Suriname amounts to an annual value of about Sf 600,000, of which two thirds represent the value of importations. There is a long standing wish to reduce imports by increasing the production and consumption of local products. The article describes the many previous attempts to establish reliable methods of cultivation, which failed because of unpredictable rainfall and the very heavy clay soil which remains waterlogged for a long time after a shower. A method introduced recently, viz. of planting pulses on ridges, has shown promising results since it avoids the difficulties of soil management. However, this method used in several experiments, needs to be adapted to the agricultural conditions of the small-holders. If the majority of rice farmers would successfully adopt this method, production could be raised to supersede the local demand by many times so that the product could be sold abroad. The selection program of pulses should then proceed as follows:

1. 1.
   to ascertain which pulses are in constant demand by the world market     

Droplet infiltration and organic matter composition of intact crack and biopore surfaces from clay‐illuvial horizons

The organic matter (OM) in biopore walls and aggregate coatings may be important for sorption of reactive solutes and water as well as for solute mass exchange between the soil matrix and the preferential flow (PF) domains in structured soil. Structural surfaces are coated by illuvial clay‐organic material and by OM of different origin, e.g., earthworm casts and root residues. The objectives were to verify the effect of OM on wettability and infiltration of intact structural surfaces in clay‐illuvial horizons (Bt) of Luvisols and to investigate the relevance of the mm‐scale distribution of OM composition on the water and solute transfer. Intact aggregate surfaces and biopore walls were prepared from Bt horizons of Luvisols developed from Loess and glacial till. The mm‐scale spatial distribution of OM composition was scanned using diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. The ratio between alkyl and carboxyl functional groups in OM was used as potential wettability index (PWI) of the OM. The infiltration dynamics of water and ethanol droplets were determined measuring contact angles (CA) and water drop penetration times (WDPT). At intact surfaces of earthworm burrows and coated cracks of the Loess‐Bt, the potential wettability of the OM was significantly reduced compared to the uncoated matrix. These data corresponded to increased WDPT, indicating a mm‐scaled sub‐critical water repellency. The relation was highly linear for earthworm burrows and crack coatings from the Loess‐Bt with WDPT > 2.5 s. Other surfaces of the Loess‐Bt and most surfaces of the till‐derived Bt were not found to be repellent. At these surfaces, no relations between the potential wettability of the OM and the actual wettability of the surface were found. The results suggest that water absorption at intact surface structures, i.e., mass exchange between PF paths and soil matrix, can be locally affected by a mm‐scale OM distribution if OM is of increased content and is enriched in alkyl functional groups. For such surfaces, the relation between potential and actual wettability provides the possibility to evaluate the mm‐scale spatial distribution of wettability and sorption and mass exchange from DRIFT spectroscopic scanning.     

Aluminium-Toleranz von Ackerbohne (Vicia faba), Lupine (Lupinus luteus), Gerste (Hordeum vulgare) und Roggen (Secale cereale). II. Mineralstoffgehalte in Sproß und Wurzeln in Abhängigkeit vom Aluminium-Angebot

Al tolerance of horse bean, yellow lupin, barley and rye. II. Mineral element concentrations in shoots and roots as affected by Al supply Inhibition of seminal root elongation by Al in solution culture gave the following ranking for Al tolerance: yellow lupin (Lupinus luteus ?Schwako”?) ? rye (Secale cereale ?Kustro)”? « horse bean (Vicia faba ?Herz Freya”?) > barley (Hordeum vulgare ?Roland”?). Exclusion from uptake by inactivation of Al outside the root was not responsible for the higher Al tolerance of lupin and rye, because comparable inhibition of root elongation occured at much higher Al concentration of the root and the root tips (5 mm) compared to barley and horse bean. The plant species differed considerable in nutrient concentrations of the roots: higher Ca concentrations in horse bean and rye, higher Mg concentrations in rye and lupin and higher P concentration in lupin. Al supply reduced Ca and Mg concentrations (Ca > Mg) in shoots and roots of all species. P concentrations were hardly affected. The nutrient concentrations in the root tips did not indicate that induction of nutrient deficiency was responsible for the effect of Al on root elongation and Al sensitivity of barley and horse bean. The considerable differences in Ca, Mg and P concentrations of the roots between the Al-tolerant plant species rye and lupin do not suggest a common physiological mechanism responsible for Al tolerance.     

Water quality in a serial‐use raceway and its effect on the growth of South African abalone,Haliotis midae Linnaeus, 1758

To quantify the effects of serial‐use of water on abalone growth and feed conversion, this study describes water quality in a serial‐use raceway with seven passes. A flow index of 7.2–9.0 L h^?1 kg^?1 was estimated as the minimum value at which to grow 60–70 mm Haliotis midae, as weight gain (analysis of variance; F_{6, 14}=13.9, P<0.0001) and feed conversion ratio (Kruskal–Wallis test; H_{6, 21}=16.3, P=0.012) were significantly reduced at lower values. pH and dissolved oxygen concentration were positively correlated with the flow index (pH, r²=0.99; P<0.001; dissolved oxygen, r²=0.99; P<0.001), while free ammonia nitrogen (FAN) and nitrite were negatively correlated with the flow index (FAN, r²=0.99, P<0.001; Nitrite, r²=0.93, P<0.001). The concentration of nitrite increased throughout the experiment and may reflect the colonization of Nitrosomonas bacteria as water re‐use increased. Based on comparisons with growth and toxicity tests, it is suggested that low pH combined with growth‐limiting levels of FAN were the first variables limiting abalone growth in the serial‐use raceway.     

Evaluation of the efficacy of vitamin D3 or its metabolites on thiram-induced tibial dyschondroplasia in chickens

Two trials were conducted to determine if thiram-induced tibial dyschondroplasia (TD) in chickens was linked to a vitamin D deficiency and calcium homeostasis dysregulation, and whether feeding vitamin D fortified diets may prevent it. Day-old chickens were given grower diets containing different vitamin D products throughout the experiment until necropsy on day 16. Half of the birds in each feed group received thiram at levels of 100 ppm (trial 1) or 50 ppm (trial 2) between days 7-9 to induce TD. The birds were weighed, bled, and euthanized to determine TD incidences and severity by examining the growth plates. Tibial bones were used to measure biomechanical strength and ash content. Blood concentrations of 25-hydroxyvitamin D, Ca, P, alkaline phosphatase, and creatine kinase were measured in serum that showed no differences between different groups. Thiram reduced body weight and induced TD regardless of any vitamin D treatment to the same extent as untreated birds.     

Effect of drying and rewetting the topsoil on root growth of maize and rape in different soil depths

The aim of the present experiments was to determine how fast maize and rape plants respond to drying and subsequent rewetting of the topsoil by changing their rooting patterns in different soil depths. Plants were grown in a glasshouse in large (120 × 10.5 × 5 cm) containers which allowed continuous observation of root growth and control of soil water contents at all depths. In both species, drying of the topsoil resulted in a rapid (after 6 d) decrease of root growth in the topsoil (0–40 cm) and an increase in the subsoil (80–120 cm). Increase of root growth in the subsoil preceded the decrease hi the topsoil. Drying of the topsoil decreased shoot P concentrations in both species, whereas the concentrations of N, K and Ca were not significantly affected despite enriched fertilizer levels in the topsoil. In both species, after rewetting, root growth in the topsoil rapidly recovered, and after 5 d exceeded that of the continuously irrigated plants. This increase of root growth an the topsoil occurred at the expense of root growth in the subsoil. The results demonstrate that maize and rape plants may rapidly respond to drying and rewetting the topsoil by locally increasing root growth in soil layers with the most favourable conditions. This plasticity in root growth is a factor which contributes to the maintenance of an adequate nutritional status.     

Stickstoffentzug durch Pflanzen als Bewertungskriterium für den Grad der Torfmineralisation

Aus vorliegenden Versuchsergebnissen werden Aussagen zum N‐Kreislauf auf Niedermoorgrünland bei gestaffelter Stickstoffdüngung gemacht. N‐Düngung und Torfmineralisation sind entscheidende Inputgrößen. Die Outputseite wird wesentlich durch Stickstoffentzüge der Pflanzen bestimmt. Die N‐Zufuhr durch Knöllchenbakterien, freilebende N‐bindende Bakterien und Niederschläge ist anteilmäßig gering. Auch sind die N‐Verluste auf Niedermoorstandorten durch Auswaschung und gasförmige Emissionen niedrig. Die Rohproteinerträge auf nicht mit Stickstoff gedüngtem, aber ausreichend mit Makronährstoffen versorgtem Niedermoor sind Anhaltsgrößen für die Mineralisationsrate des Standortes. Nach Stickstoffdüngung kann, bei einer Ausnutzungsrate von 48%, ebenfalls auf die Netto‐N‐Mineralisationsrate geschlossen werden.     

Legumes as nitrogen suppliers of grassland on fen soil: Leguminosen als stickstofflieferanten für niedermoorgrünland

A 6-year trial was laid out with varied PK fertilization on fen soil and analysed for the capability of undersown clover species to fix atmospheric nitrogen. No mineral nitrogen was applied. On an average of the six test years, the share of white clover in the total crop yield of the sward was 17% after sowing once and that of red clover or Swedish clover was 19% after sowing twice. The annual mean shares of these two clover variants in the total yield varied only slightly over the test period. White clover showed typical seasonal dynamics in the test years, with yield portions increasing from spring to late summer. Undersown red and Swedish clovers reached the highest yield percentages in their 2nd and 3rd growths. The variants grown without PK fertilizer and clover yielded 45 dt DM ha^???1. With PK fertilizer dry matter yields increased to 57 and 68 dt ha^???1, respectively. With supplemental white clover or red/Swedish clover sown into the sward, substantial amounts of symbiotic nitrogen were accumulated in the harvestable plant matter, giving a total dry matter yield of 76 dt ha^???1. Clover yield shares up to 30% resulted in increasing DM yields which, however, declined again with even larger shares of clover. As to the ingredients of grasses, herbs and clover, the differences were mostly significant. On an average of the six test years, nitrogen fixation was 58.4?kg ha^???1 for white clover and 46.6?kg ha^???1 for red/Swedish clover.     

The influence of calcium on growth of selected vegetable species in the presence of ammonium nitrogen

Growth of cabbage (Brasslca oleracea L.), cantaloupe (Cucumis melo L.), squash (Cucurbita pepo L.), chile pepper (Capsicum annuum L.), tomato (Lycopersicon esculentum Mill)., radish (Raphanus sativus L.), and Swiss chard (Beta vulgaris L.) was enhanced when supplied with additional Ca in the presence of NH₄‐N over those with normal Ca. Ammonium uptake as measured by residual NH₄ in soil leachate was lowered indicating possible increased uptake in the presence of additional Ca.