Abstract
A. field experiment was initiated during 'RAP 1 983 at the NARC experimental farms, Lslam.abadi to monitor the impact of different cropping and fertility systems on soil properties and soil productivity on. long term basis. This report considers first year results of wheat (Tririeurn arstivum L, Cv, Pak-81). Treatments included. (1) Fertilizer NE. @ 120-60-0 kg ha-' (2) Manure 20 t ha-' (3) Fertilizer NP 120-60-0 kg ha-1+ Manure ® 20 t ha-1 (4) Control - No fertilizer Or manure. All treatments significantly (P<0.01) iiffected the grain and straw yields of whear but did not affect the grain:straw ratios. Grain yield affects of the various treatments were in the order of control manure < NP < NP manure. Removal of NPK by wheat grain and straw is discussed together with the implication of a significant fertilizer . manure interaction.
INTRODUCTION
The beneficial effects from addition of organic matter to soil in Pakistan has been well established (Azad and Yousaf, 1982). Crop production has also been enhanced from the application of N and P to Pakistani soils (Chau dhary, 1983), Many federal and provincial institutes, universites and agencies are involved in conducting fertilizer trials. Little is known however, about the long term effects of fertilizer, manure and frequency of application under different cropping systems (AARI, 1 983; Anonymous. 1983 and Azad & Yousaf, 1282). The National Agricultural Research Centre at Islamabad initiated during Rabi 1983 a long terra field trial to monitor the influence of manure and commercial NP fertilizers under different cropping patterns as reflected in crop productivity and changes in soil properties, The initial crop in each cropping pattern con-
