SUMMARYTwo experiments to investigate the micronutrient requirements of cassava (cv Black Twig) on Malaysian peat soil are described. Cu was found to be the only essential micronutrient and Mn, Zn, Fe, Mo and B were not needed. Fertilizing with 20 kg/ha of copper sulphate approximately tripled tuber dry matter, and starch and Cu uptake, but applying 10 kg/ha of copper sulphate gave the same results. Each crop of cassava absorbed only about 2% of the applied Cu, giving a leaf Cu content of about 14 ppm compared with about 7 ppm in Cu-deficient plants. Cu deficiency symptoms were invariably observed in Cu-deficient plots and these are also described.

SUMMARYIn three field experiments studying the liming needs of cassava on peat, optimum tuber DM was obtained at pH 3.8 and optimum top DM at pH 4.2; liming to higher pH values decreased tuber DM while maintaining top DM. Consequently, the Harvest Index decreased over the whole range of soil pH studied (3.49–5.50). Increases in tuber DM per hectare with liming, and with an increasing growth period, were associated with mean tuber weight (r = 0.86) and with Harvest Index (r = 0.65) rather than with tuber number (r = 0.37).

S U M M A R YIn three field experiments, peat pH increased in parabolic relation to liming at the rate of 0.0544 pH unit/t/ha between 0-40 t/ha lime, but only 0.0224/t/ha between 40-72 t/ha. Groundnut and sorghum seed yield and crop residue also showed parabolic responses to peat pH and liming, but groundnut seed yield correlated poorly with soil pH (r J = 0.38, P=0.05), compared with its crop residue as well as with sorghum seed and residue (r J = 0.75, 0.76 and 0.79, respectively, P= 0.01). Groundnut was generally more tolerant of peat acidity (pH 3.35-3.65) than sorghum, giving higher plant survival in unlimed plots, optimum seed and residue at pH 4.60 compared with 5.70 for sorghum, and reduced responsiveness to pH increase. Seed and residue of both crops decreased with continuous cropping, probably because of increasing pest and disease incidence and depletion of available soil nutrients.

SUMMARYOn unlimed Malaysian peat (pH 3.5), flue-cured tobacco produced negligible leaf yields and showed no response to urea. Liming up to pH 5.25 (32 t/ha lime) linearly increased leaf yield. Tobacco responded linearly without reduced leaf quality to 90 k/ha N at pH 4.01 (8 t/ha lime), but to 45 kg/ha N at pH 4.40–5.25 (16–32 t/ha lime), higher N rates at the respective liming levels producing leaves of lower quality. The optimum rates of P and K for flue-cured tobacco appeared to be 26 and 186 kg/ha respectively, with linear responses up to those rates.

N, P and K fertilizers improved mulberry leaf, stem and fruit yields on peat, the optimum rates being ioo kg/ha/yr N, 25 kg P and 62-5 kg K, with further leaf responses to N and K if applied together in the ratio of 3:2. Harvesting every 2 months at 60 cm height gave better yearly leaf yields than cuttings 3-12 months apart, but annual stem yields were not affected by harvesting frequency and fruit yields were optimum when plants were cut at intervals of 5-6 months. Harvesting quarterly at 60 cm produced better leaf and stem yields than cutting lower (15 and 30 cm) or higher (100 and 180 cm). Two Thai cvs (Noi I and Mii) were female-sterile but the Local Malaysian producer! fruits.The Malaysian Government has shown interest since 1972 in silkworm culture as a potential cottage industry, which is now increasingly important in some states, e.g. Trengganu (Nik Yusoff, 1974). However, the success of sericulture depends on the production of adequate amounts of mulberry {Moms alba) leaves on which the growing silkworms feed, but little research has been done on mulberry production in Malaysia although it grows as a wild wayside shrub. Since information on the productivity of mulberry in relation to different agronomic and fertilizer regimes is urgently needed, the experiments reported here were conducted on peat at Jalan Kebun, where the crop was experimentally established in 1972 for observation and work on propagation by stem cuttings, though without culturing silkworms at the station. EXPERIMENTALFour field experiments, conducted during 1975-77, studied the effects of macronutrient fertilization, harvesting frequency, height of cutting and different cultivars on the productivity of mulberry, by cutting the stems at regular frequencies and not by the usual method of cutting and/or leaf plucking according to the needs of the silkworms that are being fed (Anon., 1973). The treatments were:Experiment I-o, ioo and 200 kg/ha N as urea; 0, 25 and 50 kg/ha P as superphosphate; ando, 62-5 and 125 kg/ha K as potassium sulphate, with all levels factorially combined. Experiment 2-Harvesting at frequencies of 2, 3, 4, 5, 6, 8, 10 and 12 months, Experiment 3-Harvesting at heights of 15, 30, 60, 100 and 180 cm, and