| The studies were conducted in the two consecutive years (2003-2004) to determine the effects of planting patterns, thinning within rows, spacing and intraspacing fertilizer application , foliar application of plant growth regulators, cutting on alfalfa seed yields, yield components and quality parameters in Jiuquan, Gansu province. The results indicated that:l.Spacing and intraspacing show significant main effects on alfalfa seed yield and yield components(P<0.05). With the increase of spacing and intraspacings from 60cm and 15cm to 100cm and 60cm, seed yields decreased form 1240 kg/hm2 and 1426 kg/hm2 to 982 kg/hm2 and 807 kg/hm2 respectively. 60cm x 15cm treatments recorded the highest yield with 1833 kg/hm2, and 100cm x 60cm treatment , the lowest, 753 kg/hm2. Fertile shoots per square meter drop significantly, and pods/stem increase significantly (P<0.05). Spacing and intraspacing did not affect seed no./pod and seed weight significantly(P>0.05).Significant differences were found in seed weight, hard seed percentage, normal seedlings, first counts between varieties(P<0.05).2. Thinning within rows significantly increased seed yields(P<0.05).The highest seed yield 364kg/hm2and 353kg/hm2 was both obtained in 45cm- thinning treament plots , 64%and 37.9% up than untreated plots(CK). Significant effects of thinning on seed-yield components were also determined. Thinning significantly decreased fertile shoots/m2, and increased florets/inflorescence, inflorescences/shoot, racemes/shoot, and pods/racemes(only in 2004) in the two consecutive years, however, seeds/pod and 1000-seed weight were not affected accordingly. Seed quality index including first count, hard seed, standard germination were not affected significantly by all the thinning treatments.3.Phosphorus application significantly increased fertile shoots/m2, racemes/shoots,and the subsequent seed yield(P<0.05). The application rate of 60 kg/hm2 record 1281 kg/hm2, the highest seed yield among all the treatments. The mixed application of Phosphorus and Potassium did not show significantly positive effects on seed yield(P>0.05), but increase seed germination rate, normal seedlings significantly(P<0.05).4.The manipulation of plant growth regulators on alfalfa plant growth were detected in the two years. In 2003, NAA and PP333 significantly increased seed yield, (P<0.05) the highest increasing rate amounted to 74 and 42% respectively. Application of B-nine and CCC significantly reduced plant height only in one year(P<0.05).All the four plant growth regulators showed insignificant effects on seed yield in 2004, indicating the important role of weather conditions and stand ages in the effectiveness of plant growth regulators. Some of the growth regulators significantly affect seed quality parameters including hard seed percentages in both years (P<0.05) .5. The highest seed yield (1040.5kg/hm2) was obtained in uncut plots (CK), while the seed yield of the cutting on 24 May dropped significantly to 845.3 kg/hm2. With the advancing of the cutting time,pods/racemes and seeds/pod increased accordingly, while florets/inflorescence and thousand-seed-weight (TSW) declined significantly. Seed quality was also influenced significantly by cutting treatments. Normal seedlings percentage and hard seed percentage were decreased significantly by cutting, however, as the main indicator of seed quality, the standard germination did not differ significantly among the treatments.In addition, cutting treatment significantly affected alfalfa growth stage and their durations, and postpone the seed ripen stage (P<0.05). Based on this founding, the cutting technique is as such recommended in large-scale alfalfa seed production , to reduce the loss of pod shedding caused by compulsory postponed harvesting due to the shortage of labors and machines in the intensive seed ripening period.
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