Sesbania sesban was evaluated as green manure crop for lowland rice in the Dry Zone of Sri Lanka. The legume was grown during a fallow period before lowland rice (Oryza sativa) and ploughed under just before transplanting. Weight loss and nitrogen content in litterbags containing leaves, stems and roots of the legume were monitored. Comparisons were made between rice yields from 20m 2 plots after green manuring in combination with different nitrogen fertilizer levels (0, 2.4, 4.8 and 7.2gm z) and nitrogen fertilizer (9.6 g m 2) alone. Above-ground biomass of S. sesban was 440 g m 2 (dry wt) when ploughed under after 84 days growth. N-content in leaves, stems and roots was 3.760,0.41% and 0.73%, respectively. This gave a N-input from S. sesban of 9.2 g m 2 (8.3 g from above-ground parts and 0.9 g from roots). The corresponding K and P inputs were 7.3 and 0.6gm 2 respectively. The nitrogen rich leaves, which contained 88% of the nitrogen in the above-ground parts, decomposed and released its nitrogen much more rapidly than the stems and roots. After only four days the leaves had released 5.3 g N m -2 and after 14 days they had released 6.4 g N m 2. The highest rice yield (505 g m 2) was obtained using S. sesban and 4.8 g m 2 of N-fertilizer. The yields with only N-fertilizer or only S. sesban were 442 g m -2 and 396 g m -2, respectively. Due to the rapid decomposition of the nitrogen rich leaves, S. sesban did not behave as a slow release fertilizer. Thus, it is not necessary to apply nitrogen fertilizers as a basal dose.

The Labiatae is a large family of diverse morphology and habit. Almost all members contain phytochemicals, volatile oils which contribute variously to commercial value, problems of toxicity and allelopathic activity. Weed status in the Labiatae depends primarily on competition tor environmental resources and on characteristics dependent on the phytochemical content. In a number of genera, notably Salvia, allelopathic activity has been documented.

Summary: Résumé: Zusammenfassung Some germination of Salvia reflexa Hornem. could occur from 4 to 39°C, with good germination between 12 and 32°C and the best germination at 28 and 32°C. Rate of germination and total germination were decreased as osmotic potential of the germination medium increased from ‐0.4 to ‐ 1.4 MPa. Germination thus occurred at a higher osmotic potential than in most species previously reported. This wide tolerance of environmental factors affecting germination should enable S. reflexa to be competitive over a wide range of field conditions. In field studies of emergence, when new seed formation was prevented, germination occurred in spring as soils warmed up and rainfall became adequate and continued to mid‐summer when drought occurred. When seed fall was allowed from these spring emerging plants there was a further period of autumn germination, but this was not evident in disturbed plots with no seed return. These patterns conformed with expectations based on laboratory germination studies. Etudes sur Salvia reflexa Hornem. III. Facteurs qui en règlent la germination Salvia reflexa Hornem. est capable de germer à des températures allant de 4 à 39°C; une bonne germination a lieu entre 12 et 32°C et la meilleure se produit à 28–32°C. Le taux de germination ainsi que la germination globale ont baisséà mesure qu'augmentait de −0, 4 à−1, 4 MPa le potentiel osmotique du milieu de germination. La germination s'est donc produite à un potentiel osmotique plus élevé que chez la plupart des espèces signalées précédemment. Cette large tolérance de facteurs qui influent sur la germination donnerait à.V. reflexa une capacité de concurrence dans une large gamme de conditions sur le terrain. Dans des études de la levée au champ, lorsque la production de graines nouvelles avaient été bloquée, la germination s'est produite au printemps à mesure que le sol se réchauffait et que la précipitation devenait suffisante; elle a continué jusqu'à la sécheresse du plein éte. Lorsque les graines de ces plantes qui avaient levé au printemps ont pu tomber, une germination ultérieure a eu lieu en automne; ce phénomène ne s'est pas produit dans des parcelles remuées et sans chute de graines dans le sol. Ces modalilés s'accordent aux prévisions faites à base d'études de germination en laboratoire. Untersuechungen an Salvia reflexa Hornem. III. Keimung Samen von Salvia reflexa Hornem. keimten zwischen 4 und 39°C, aber im wesentlichen zwischen 12 und 32°C, und das Optimum lag bei 28 bis 32°C. Mit dem Ansteigen des osmotischen Potentials des Keimmediums von ‐ 0, 4 auf ‐ 1, 4 MPa nahm die Keimrate ab. Die Keimung lag also bei einem höheren osmotischen Potential als bei den meisten Arten. über die vorher berichtet wurde. Diese weite physiologische Spanne der Keimung sollte es S. reflexa erlauben, unter verschiedenen ökologischen Bedingungen mit anderen Arten zu konkurrieren. In Feldversuchen keimten die Samen vom Frühjahr, nachdem sich die Böden erwärmten und ausreichend Niederschlag gefallen war, bis zum hohen Sommer, wen...

Summary: Résumé: Zusammenfassung Plants of Salvia reflexa Hornem. grown in pots of soil were subjected to drought treatments in glasshouse conditions. Quite short durations of water stress significantly decreased leaf area, top and root dry weight and the plants rapidly adjusted their water loss below potential evaporation rates. The plants survived and recovered from periods of drought for up to 30 days but plants dehydrated, even after short droughts, did not attain the growth rates of undroughted plants. In an infertile soil, S. reflexa plants demonstrated a large requirement for applications of phosphorus. With phosphorus applied, the species was also very responsive to nitrogen, and where both nitrogen and phosphorus were applied there were smaller responses to sulphur and potassium. Etudes sur Salvia reflexa Hornem. IV. Influence exercée sur la croissance et le développement de l'espèce par la fréquence des arrosages, la sécheresse et l'apport d'aliments Salvia reflexa Hornem., cultivé en vases de végétation, a été soumis à des régimes de sécheresse en conditions de serre. Une sécheresse, même de durée assez courte, a amené une diminution significative de la surface foliaire et du poids sec des parties aériennes ainsi que des racines; les plantes ont vite fait d'adapter leur perte d'eau à des niveaux inférieurs au taux potentiel d'évaporation. Elles ont survécu et se sont remises après des sécheresses de 30 jours maximum mais les plantes déshydratées, même pendant des sécheresses de courte durée, n'ont plus atteint le taux de croissance des plantes i indemnes de sécheresse. En terre pauvre, les plantes de S. reflexa ont exigé de grands apports de phosphore. Après les apports de phosphore, l'espéce a également fait preuve d'un grand besoin d'azote. En présence de phosphore et d'azote, la réponse aux apports de soufre et de potassium était moins forte. Untersuchungen an Salvia reflexa Hornem. IV. Einfluss von Wasserversorgung und Düngung auf das Wachstum In Gewächshausversuchen mit Salvia reflexa Hornem, nahmen bei relativ kurzzeitiger Trockkenperiode die Blattfläche und die Trockenmasse des Sprosses sowie der Wurzeln signifikant ab, so dass die Pflanzen die Transpiration schnell unter die potentielle Evaporationsrate senkten. Sie überlebten Trockenperioden von bis zu 30 Tagen und erholten sich wieder, erreichten aber, auch nach kurzem Wassermangel, nicht dieselben Wachstumsraten wie Pflanzen, die nicht dieser Belastung unterworfen waren. Auf einem nährstoffarmen Boden zeigten S.‐reflexa‐Pflanzen einen hohen Phosphatbedarf. Nach Phosphatdüngung braucht die Art auch viel Stickstoff. Bei N + P‐versorgten Pflanzen ist der Bedarf an Schwefel und Kalium gering.

Sri Lankan rice farmers rarely practise green manuring and they depend mostly on chemical fertilizers for the nutrient requirement of their crops. With the removal of government subsidy on fertilizers since 1990, they are now faced with the dilemma of meeting the cost of production to sustain previous yield targets. Therefore the present study devotes to evaluate alternative cheaper nutrient sources like green manures for rice. Results of recent work in Sri Lanka have shown that Sesbania speciosa Taub. ex Engl.is a promising green manure for lowland rice in the dry zone. It was evaluated to adopt a suitable green manuring system for rice. Its year-round biomass production, nutrient accumulation during the vegetative growth and nitrogen fixation were monitored. Field trials were conducted to investigate its ability to suppress weed growth when grown during fallow periods and its contribution to soil fertility and effect on rice yield. Highest biomass of around 100 g dry matter per plant, was achieved when S. speciosa was seeded in August and harvested at flowering in November. When this was planted during a fallow period at a spacing of 0.25 x 0.25 m (16 plants m 2), percentage weed reduction was as much as 40%. Its N 2 fixation activity was similar to that of S. sesban (L.) Merr.. Nitrogen concentration in S. speciosa increased until 70 days after establishment and then decreased towards flowering. Phosphorus and K accumulation was also effective during this period. Therefore suitable time for soil-incorporation of S. speciosa is around 70 days after establishment. S. speciosa-manured and chemically fertilized rice crops were comparable in terms of grain yield, indicating the effective nutrient supplying potential of this green manure. Straw biomass was significantly high under S. speciosa, because of the high N-allocation to vegetative growth of rice under this. This evaluation shows that S. speciosa not only supplies N, but is also an effective and complete supplier of other nutrients for rice. A scheme to introduce this into rice production system is proposed, where S. speciosa is seeded/broadcast two weeks before crop harvest (around January) in Maha (major) season as well as Yala (minor) season (around June) so that its biomass can be incorporated into soil during land preparation of subsequent seasons.