SUMMARYHerbage and oil yields of Mentha arvensis (Japanese mint), M. piperita (peppermint) and M. spicata (spearmint) increased significantly with N fertilization up to 100 kg N/ha and those of M. citrata (bergamot mint) with up to 150 kg N/ha. Plant height, leaf: stem ratio and leaf area index increased with N application; and oil content decreased in all the species. Economic optimum doses of N for M. arvensis, M. piperita and M. spicata were 167, 153 and 145 kg N/ha, respectively and their oil yields expected from the response equation were 190, 103 and 50 kg/ha, respectively. The calculated optimum fertilizer rate for M. citrata was 225 kg N/ha, giving a yield of 193 kg oil/ha. Oil quality did not vary appreciably with N fertilization.

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A number of field experiments were conducted at the Viswavidyalaya Research Farm during 1984–85 to 1986–87 to study the effects of five growth regulators viz. Miraculan (a triacontanol based growth stimulant), Nutron (1‐triacontanol growth stimulant), Planofix (α‐napthylacetic acid), Paras or Mixtalol (Higher alcoholic carbon compounds) and N‐triacontanol on productivity of five different major oilseed crops viz. rapeseed (Brassica campestris L. var. yellow sarson), mustard (Brassica juncea L. Czern and Coss), sesame (Sesamum indicum L.), linseed (Linum usitatissimum L.) and safflower (Carthemus tinctorius L.). Results showed the positive influence of growth regulators on the productivity of crops (10–40 % increase in yield); however the influence was not consistent over the years. N‐triacontanol when tried on mustard only improved the grain yield significantly, more so when applied with paras or planofix, sesame was most influenced by spraying planofix and paras. Nutron favourably influenced safflower and linseed. The test weight of grains followed by the number of pods/plant were influenced most by the application of growth regulators. Inconsistency in results over the years, however, need further investigations on the timing of spraying.

To increase the productivity of fields growing direct-seeded upland rice, which usually gives low yields because of weed competition, unsatisfactory establishment and exposure to intermittent drought, an experiment on intercropping of rice with blackgram was conducted in two seasons under rainfed conditions on a sandy loam soil. Blackgram, when intersown simultaneously in one row in every 30 om wide space left between the stand of 10 cm apart paired rows of rice, reduced the yield of rice by 1-64 t/ha. When one row of blaokgram was intersown, 21 days after sowing of rice (after completing weeding) between the paired rows of rice, rice yield was reduced by only 0-24 t/ha compared with sole cropping of rice with weeding. This system provided mean yields of 2-48 t/ha of rice and 0-95 t/ha of blackgram. The price of blackgram being high, it showed a mean monetary advantage of Rs. 2373/ha over sole cropping of rice. The blackgram reduced the weed population appreciably. INTRODUCTIONIntercropping is an important feature of tropical agriculture. One advantage claimed for this farming system is that it gives an insurance against crop failure. In India, where intercropping is a widespread practice, many crop combinations are used and in most cases a grass and a legume are mixed. Upland direct-seeded rice crops are extensively cultivated in India but the yield of upland rice is usually low because of poor stands, adverse competition from weeds and intermittent drought. Blackgram (another important food crop extensively grown in the uplands of India) under similar condition has good growth, competes with weeds and being deep-rooted suffers less from drought.The present investigation was undertaken to Study the feasibility of intercropping upland rice with blackgram, the growth and yield of rice and blackgram grown as sole crops and as a mixture and the effects on weeds when the blackgram was established 2-3 weeks after the rice was sown or when both the crops were sown at the same time.

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