Yields and N2 fixation of lentil and chickpea as influenced by tillage and P levels under rain-fed conditions

The influence of two tillage (plough, no-plough) and two P levels (30 and 60 kg P205 ha-1) on yield and N2 fixation of rain-fed lentil (Lens culinaris) and chickpea (Cicer arietinum) was investigated in a field experiment at farmer's field of Peshawar valley. The experiment was commenced with lentil and wheat in the 1998/99 winter followed by wheat in the 1999/00 winter. In the following 2000/01 winter, lentil was replaced by chickpea and finally had wheat in the 2001/02 winter. The experiment was laid out in a split plot design with three replications keeping tillage in the main and P levels in the sub plots. Micro-plots of 1 m2 were also established in each treatment plot of lentil and chickpea fertilized with 15N labeled urea (5% 15N atom excess) at 20 kg N ha-1 at sowing time for N2 fixation and N fertilizer utilization studies. The effect of tillage was different for the two crops. It improved the grain yield of lentil by 32% (250 kg ha-1) and straw yield by 25% (308 kg ha-1) but reduced the grain yield of chickpea by about 38% (40 kg ha-1) probably because of very little rain received for chickpea (85 mm) than for lentil (268 mm). However, differences in grain and straw yields of lentil or chickpea between the two P levels were not significant. Both tillage and P levels had no remarkable effects on N derived from air (%Ndfa), fertilizer (%NdFF), or soil (%NdFS) by lentil. Although %Ndfa by lentil was not affected by tillage, the amount of N2 fixed was substantially greater in the tillage (64.32 kg ha-1) than in the no- tillage treatment (46.08 kg ha-1) with similar differences in crop N yield between the tillage (74.07 kg ha-1) and no-tillage treatment (52.81 kg ha-1). The amount of N2 fixed by lentil was also greater at 60 than at 30 kg P ha-1. For chickpea, %NdFF, %NdFS, crop N yield and fertilizer N yield were slightly greater for tillage than for the no-tillage treatment. In contrast %Ndfa and N2 fixed by chickpea were greater in the no-tillage than in the tillage treatment. P levels had no affect on any of the parameters studied for chickpea. It was however observed that both yield and N2 fixation of chickpea were very low because of low rainfall, it is difficult to ascertain any treatment effect under such circumstances. Our results suggested that tillage improved the yield of lentil with no remarkable effect on N2 fixation but did not help to improve the yield and N2 fixation of chickpea when rainfall was very low. Fertilizer P at 60 kg ha-1 did not improve the grain yield or N2 fixation of lentil, and chickpea compared with that at 30 kg suggesting that application of fertilizer P is not needed under the prevailing circumstances.