Plant and Soil 114, 135-138 (1989) ~i) 1989 KluwerAcademicPublishers. Printed in the Netherlands PLSO 7814 Response of field-grown chickpea (Cicer arietinum L.) to phosphorus fertilization for yield and nitrogen fixation MOHAMMAD IDRIS, TARIQ MAHMOOD and KAUSER A. MALIK Nuclear Institute.for Agriculture and Biology (NIAB), P.O. Box 128, Jhang Road, Faisalabad, Pakistan Received 25 May 1988. RevisedOctober 1988 Key words: chickpea, phosphorus, nitrogen fixation Abstract Application of phosphorus at 40, 60, 80 and 100kg P2Osha -~ in the presence of a uniform dressing of nitrogen (N) and potash (K20) each applied at 20 and 24 kg ha-~ to chickpea (CM-88) grown in sandy loam soil in a replicated field experiment improved the nodulation response of the crop, increased its grain yield (kaha -~) by 18, 59, 40 and 14 percent, biomass yield (kaha -~) by 32, 32, 54 and 14 percent, biomass N (kgha ~) by 31, 48, 49, 19 percent, and biomass P (kgha -~) by 26, 40, 41 and 11 percent, respectively. The effect of phosphorus on the nitrogenase activity of the excised roots of chickpea was, however, inconsistent. Introduction Chickpea (Cicer arietinum L.) is the principal winter pulse crop grown in Pakistan. The area under chickpea cultivation in Pakistan is 919 thous- and hectares, producing about 521 thousand ton- nes annually (Agricultural Statistics of Pakistan, 1984). It is a significant component of rainfed crop- ping system, and is mainly grown on non-irrigated, sandy soils without any fertilizer application. Like other food legumes, chickpea contains con- siderably more protein than most other food crops. This makes it an excellent complementary crop to be grown with cereals in rainfed areas of Pakistan. Its symbiotic relationship with nitrogen-fixing bac- teria (Bradyrhizobia) in the nodules, which is the main reason for its high protein content, also ena- bles this crop to survive and flourish on soils con- taining low levels of nitrogen, provided the crop is effectively nodulated. Its average yield in Pakistan is very low, ranging from 465 to 800kgha ~, with a mean yield of 568kgha ~ (Agricultural Statistics of Pakistan, 1984). The low yield of the crop in Pakistan is primarily due to genetic, agronomic and economic factors. From an agronomic point of view, nutri- tional deficiency is likely to depress its nitrogen- 135 fixing role and may in turn limit the yield of the crop. Most of the cultivated soils of Pakistan are defi- cient in available nitrogen in particular and in available phosphorus in general (Wahhab, 1965). This situation is even more serious in sandy soils. Being a nodulating crop chickpea can fix atmo- spheric nitrogen to meet its own nitrogen require- ment. However, favourable growth, yield, nodula- tion and nitrogen fixation responses of chickpea are expected to the application of phosphorus, when grown in soil responsive to this nutrient element. The present work was carried out to study the response 9f chickpea to phosphorus fertilization under field conditions at Faisalabad and to meas- ure its effect on the growth, yield and nitrogen fixing capacity of the crop. Materials and methods The experiment was conducted with chickpea (CM-88) during the winter season (October-April) of 1985-86 in the experimental area of the Nuclear Institute for Agriculture and Biology (NIAB) in Faisalabad. The soil at the experimental site was sandy loam in texture (pH = 8.3 and