Field experiments were conducted to determine the physiological and biochemical basis of the interactive effect of sulphur (S) and nitrogen (N) application on seed and xanthotoxin yield of Ammi majus L. Six treatments were tested (T1 = control-without manure and fertilizers, T2 = manure @ 9 kg plot-1-10~;t~;ha-1,~;T3=A0N50K25P25,~;T4=S40N50K25P25,~;T5=S40N100K25P25~;T6=S20+20N50+50K25P25) ). Nitrate reductase (NR) activity and ATP-sulphurylase activity in the leaves were measured at various phonological stages, as the two enzymes catalyze rate-limiting steps of the assimilatory pathways of nitrate and sulphate, respectively. The activities of these two enzymes were strongly correlated with seed and xanthotoxin yield. The highest nitrate reductase activity, ATP-sulphurylase activity and xanthotoxin yield were achieved with the treatment T4 . Any variation from this treatment decreased the activity of these enzymes, resulting in a reduction of the seed and xanthotoxin yield in Ammi majus L. The higher seed and xanthotoxin yield achieved in Ammi majus L. at treatment T4 could be due to optimization of leaf soluble protein and photosynthetic rate, as these parameters are Influenced by S and N assimilation.

Randomized field experiments were conducted to study the interactive effect of sulphur (S) and nitrogen (N) on seed, oil and protein yield of two cultivars of groundnut Arachis hypogea: cv Amber (V1) : cv Kaushal, (V2) . Two dosage levels of sulphur (0~;and~;20kg~;ha-1 ) and two dosage levels of N (23.5~;and~;43.5kg~;ha-1 ) in various combinations were tested as micronutrient treatments, T1,~;T2,~;and~;T3 . Results indicated significant enhancement of the yield components namely seed and oil yield as well as seed protein. Maximum response was observed with treatment T3 (having 20kg S and 43.5kg N ha-1) . Increase in seed and oil yields of 90% and 103% in V1 , and 79 and 90% in V2 , respectively were recorded as compared to the control treatment T1 (having 0kg S and 23.5kg N ha-1 ). Effect of S and N interaction was observed on protein, N and S content in seeds. The results obtained by these experiments clearly suggest that judicious balanced application of N and S could improve the yield.

A number of field experiments were conducted to assess the role of combined application of nitrogen and sulfur to increase the seed and oil yield of nonnodulating soybean (Glycine max (L) Merr.) cv. PK-416 (V1) and cv. PK-1024 (V2) . Six combinations of N and S in three replicates each were used for this purpose i.e. 0~;S+23.5kg~;N~;ha-1(T1);~;0~;S+23.5+20kg~;N ~;ha-1(T2);~;40~;S+23.5kg~;N~;ha-1(T3);~;40~;S+23.5+20kg~;N~;ha-1(T4);~;20+20~;S+23.5kg~;N~;ha-1(T5);~;20+20~;S+23.5+20kg~;N~;hal(T6) . Nitrate reductase (NR) and ATP-sulphurylase activities in the leaves were measured at various growth stages as the two enzymes catalyze the rate limiting steps of the assimilatory pathways of nitrate and sulphate, respectively. The activities of these enzymes were strongly correlated with seed yield. The higher seed, oil and protein yields were achieved with the treatment T6 in both the cultivars due to optimization of NR activity and ATP-sulphurylase activity, as these parameters were influenced by N and S assimilation. Any variation from this combination was observed to decrease the activity of these enzymes resulting in reductions in the seed, oil and protein yield of soybean.

A field experiment was conducted to assess the growth characteristics, seed and oil yield of two cultivars of soybean (G max (L.) Merr.) cv. PK-416 (V1 ) and cv. PK-1024 (V2 ) in relation to sulphur and nitrogen nutrition. Six combinations (T1-T6 ) of two levels of sulphur (0 and 40 kg ha-1 ) and two levels of nitrogen (23.5 and 43.5 kg ha-1 ) were applied to the two soybean cultivars as nutrients. Results indicated significant effect of sulphur and nitrogen, when applied together, on the growth characteristics, yield components, and seed and oil yield. Maximum response was observed with treatment T6 (having 40 kg S and 43.5 kg N ha-1 ). Seed and Oil yields were increased 90 and 102~% in V1 > and 104 and 123~% in V2 , respectively as compared to the control i.e. T1 (having 0 kg S and 23.5 kg N ha-1 ). Positive responses of S and N interaction on leaf area index, leaf area duration, crop growth rate and biomass production were also observed. The results obtained in these experiments clearly suggest that balanced and judicious application of nitrogen and sulphur can improve both seed and oil yield of soybean cultivars by enhancing their growth.