Seed yield and its components of Brachiaria decumbens cv. Basilisk, Digitaria milanjiana cv. Jarra and Andropogon gayanus cv. Kent in north-east Thailand under different rates of nitrogen application

In a study of seed yields of pasture grasses in Thailand, pure seed yields of Brachiaria decumbens cv. Basilisk, Andropogon gayanus cv. Kent and Digitaria milanjiana cv. Jarra in one season were 81-123 kg/ha, 326-569 kg/ha and 48-97 kg/ha, respectively. Corresponding thousand-seed weights were 4.68, 3.35 and 0.42 g. Germination rates were 36, 73 and 17% at 4-6 months post harvest. In Thailand, low plant density and seeds per inflorescence, not moisture availability, are likely to be the most important factors causing low seed yields of B. decumbens. Seed production and quality of A. gayanus were exceptionally high, while seed yields of D. milanjiana were similar to reported values. The nylon gauze seed collection bags facilitated full seed retrieval. Nitrogen application increased seed yield and inflorescence density but produced significant lodging in all species at 200 kg/ha N on this sandy loam. However, it did not affect seed weight, purity, germination or viability of any of these species. Seed yields of B. decumbens in Thailand are characteristically low and present results indicate that low plant density and few seeds per inflorescence are contributing factors. The reasons for this are unknown. Gamba grass (Andropogogon gayanus), with its drought-resistant characteristics, high dry matter production, high seed production and quality and low nitrogen requirement for seed production is a useful addition to pasture options for north-east Thailand

Status of Stylosanthes development in other countries.II. Stylosanthes development and utilisation in China and southe-east Asia

Introduction of Stylosanthes species to south-east Asia commenced in 1949 and tended to follow the development of commercial cultivars in Australia. S. guianensis cultivars were introduced to humid and subhumid areas in Malaysia, Indonesia, southern Thailand, Philippines and China. S. humilis, S. hamata and S. scabra were introduced to drier areas in the region such as north-east Thailand, eastern Indonesia and southern China. Anthracnose severely reduced growth and survival of many cultivars used in the region. In 1976, an outbreak of anthracnose in S. humilis prompted a change to S. hamata cv. Verano in Thailand. S. guianensis cv. Schofield was similarly affected in many countries and was replaced by Cook and Graham. Later Cook and recently Graham were similarly affected in many countries and are being replaced by S. guianensis CIAT 184. The most widely used species today are S. hamata cv. Verano, and S. guianensis cv. Graham and CIAT 184. S. hamata is used mainly in north-east Thailand for inclusion in heavily grazed pastures. In 1995, 150 t of seed of S. hamata was produced in Thailand. S. guianensis cv. Graham and CIAT 184 are grown on more than 100 000 ha in monoculture, often associated with perennial tree crops in southern China. It is used as fresh feed for ruminants, or dried and processed as leaf meal. Recently, S. guianensis CIAT 184 has gained popularity in more countries in south-east Asia because of its broad adaptation, potential for multiple uses and high productivity in acid, infertile soils. Prospects for increased use of this species, particularly in smallholder farming systems, are excellent

Effect of date of closing cut on seed yield and its components of Andropogon gayanus cv. Kent

The effect of date of closing cut on seed production of Andropogon gayanus cv. Kent was studied in NE Thailand. Cutting in August, September or October produced progressively lower pure seed and pure live seed yields than the uncut control (433.9 vs 285.2, 159.3 and 62.1 kg/ha; and 302.6 vs 206.7, 99.2 and 38.6 kg/ha, respectively). Delayed peak flowering in association with increasing moisture stress, and a reduced leaf area at flowering may have led to decreased yields. Thousand-seed weight was unaffected by cutting date. Tiller density increased with later cuts, but as inflorescence density remained similar, tiller fertility decreased. Seed purity was unaffected by cutting date. Closing cuts had a large, negative effect on inflorescence size, indicated by dramatic reductions in pure seed yield per inflorescence with successive cuts. Seed germination percentage decreased following cutting in September or October, resulting in lower pure live seed yield. Closing cut dates between May and August should be investigated

Incidence of subclinical toxicity in goats and dairy cows consuming leucaena (Leucaena leucocephala) in Thailand

A survey of the leucaena toxicity status in four major goat-producing provinces of Thailand where leucaena is fed as the principal dietary component was conducted. Three adjacent dairy farms in one province where leucaena silage was being fed were also sampled. Urine samples were collected from 63 animals on six goat farms and from 32 cows on three dairy farms. Samples were acidified, cleaned and analysed by high performance liquid chromatography for 3,4-DHP and 2,3-DHP concentrations, using a modified procedure developed at the University of Queensland. Total DHP concentrations varied from 375 to 3357 μg/mL on goat farms, and from 142 to 182 μg/mL on dairy farms. These concentrations are indicative of subclinical toxicity that might cause reduced feed intake and productivity. The impact of high DHP on productivity needs to be further studied because leucaena is a readily available source of high-protein forage for ruminant industries in Thailand