Abstract: In order to clarify the effect of sowing date and interplanting pattern on carboxylase activity and grain yield of summer maize and to provide research support for decision-making on interplanting pattern and sowing date,field experiments were conducted in the years 2008 and 2009.The experiment included four treatments of maize sowing dates,June 1,6,11 seeded inter-rows of previous wheat,and June 16 directly-seeded after wheat harvest,and the four treatments were expressed in S_06-01,S_06-06,S_06-11 and S_06-16 respectively.Carboxylase activities were determined during growing period of maize.The main results showed that,with delaying sowing dates,the activities of RuBPCase and PEPCase increased,and the ratio of PEPC/RuBPC decreased for leaves 1-4 of maize.The PEPCase activities of the three-ear-leaves of maize showed single peak changes with growing process.Early sowing maize leaves fully expanded earlier,their peak of PEPCase activity also appeared earlier and decreased more sharply during late periods.As a result,the difference of average PEPCase activities of three-ear-leaves during growing period among the four treatments was insignificant.The photosynthetic potential and leaf source capacity decreased with delay of sowing date,however,the bearing ears of maize increased as sowing date delayed.1 000 grains weight was closely related to the temperature during filling period but less related to the sowing date.The grain yield and the harvest index of directly-seeded summer maize can be the same as,or higher than,those seeded inter-rows of previous wheat.Directly-seeding summer maize after wheat harvest was convenient for entire mechanization of wheat-maize double cropping,and therefore the most suitable cropping pattern for wheat-maize production.To avoid the concentrated period of irrigation after summer maize directly-seeding,however,seeding summer maize inter-rows of previous wheat not earlier than nine days before wheat harvest (after June 6),may provide longer period for farming operation during wheat harvest and maize sowing.

Key words: Summer maize, Sowing date, Interplanting pattern, Carboxylase activity, Grain yield

CLC Number: 

• S513.01