Effects Of Irrigation And Nitrogen Fertilizer On Corn For Seed Production In Hexi Corridor

As is well known to all, the largest corn seed production base is in Hexi corridor, Gansu province. However, there is many problems in seeds production, such as, no a rule for determine of harvest time, over use of irrigation and fertilizer resources is a common phenomenon. Firstly, a field experiment was conducted in Wuwei of Gansu province in 2013, test material were ZD958, XY335, JX1. We measured seed moisture, 100-seed weight, standard germination rate, quenching germination rate and electrical conductivity of seeds in different harvest time, the objective was to determine the relationship between the harvest time and seed vigor, and the reasonable date for seed harvest, base on this study, another field experiment was conducted in Zhangye of Gansu province in 2014, including three irrigation levels(3000, 4500 and 6000 m3·hm-2) and three nitrogen applied levels(0, 225 and 450 kg·hm-2). We measured seed yields, agronomic traits, growth development, water and nitrogen use efficiency, milk line development and electrical conductivity of seed in different harvest time, the objective was to know the effects of irrigation and nitrogen application rates on seed yield, use efficiency of water and nitrogen, seed vigor during different harvest date.The results was a theoretical basis which was used to determine the reasonable harvest date of seed, and an optimal irrigation and nitrogen application rate for high vigor seeds production. The main results were follows:1. The relationship between seed maturity degree and seed vigor: seed moisture decreased and 100-seed weight of seeds increased with harvest stage development, a closely relationship between seed vigor and seed maturity was found in the three hybrid seeds(ZD958, XY335 and JX1). Both the vigor index and the field germination rate were greatest at 57 days after pollination,when the standard germination of seeds was 97% for XY335, 95% for ZD958 and 97% for JX 1, respectively, the quenching germination rate of seeds was 94%, 84% and 79%, respectively, the electrical conductivity of seeds was decreasing to a stable value, the field germination rate reached 95%, 95% and 95%, respectively, and the milk line development of seeds was at the third stage(the milk line is at middle of grain), seed moisture is at 38%-40%.2. The yield of XY335 seed was significant higher than that of ZD958 seed. The highest yield of XY335 was 11147.2 kg·hm-2 under W4500N450 treatment; the highest yield of ZD958 was of 7520.4 kg·hm-2 under W3000N225 treatment, the peak of seeds yield was not at high irrigation and high nitrogen rates treaments. Main reason for the difference of yield was which different irrigation and nitrogen significantly influenced the spike grain number and 100-seed weight of seeds. Dry matter accumulation of corns for seed production under nitrogen applied treatments were significantly higher than those of no nitrogen applied treatments at same sampling date, after stress irrigation, as to XY335, dry matter accumulation rate under N225 treament was significantly higher than those of N0 and N450 treatments under W3000 levels, but growth rate was increasing with increasing of nitrogen applied rates under W4500 and W6000 irrigation level, as to ZD958, the dry matter accumulation rate under N225 treament were significantly higher than those of N0 and N450 treatments under W3000 and W4500 irrigation levels, and the growth rate under nitrogen applied treaments were significantly greater than no nitrogen applied treatment.3. The water consumption of treaments were no difference without irrigation stress, but after irrigation stress, the stages water consumption of treaments was increasing with the increasing of irrigation rate, 0-100 cm soil profile of NO3--N accumulation amount under W4500 irrigation rate was significantly higher than that of W3000 treament and W6000 treament.There was not a significant difference in water use efficiency between nitrogen treatments under W3000, the water use efficiency under N225 and N450 treatment were significantly higher than that of N0 treatment under W4500 and W6000, but there was not significant difference between N225 and N450 treatments. As to ZD958, the highest water use efficiency was under W6000N450 treatment, as to XY335, was under W4500N225. Nitrogen partial productivity, nitrogen agronomic efficiency and nitrogen use efficiency of N225 were significantly higher than that of N450 treatment under the same irrigation level.4. A significant effects of irrigation and nitrogen application rates on milk line development of seeds was found, seed moisture of XY 335 was significant lower than those of ZD 958 in early stage of sampling, decreasing of XY 335 seed moisture was faster than ZD 958 in early stage of seed forming. With the increase of irrigation levels, milk line development of ZD 958 seed has a tendency to delay, and irrigation did not affected milk line development of XY 335. With developing of harvest stage, the electric conductivity of seeds gradually decline under different irrigation and nitrogen treatment, the seed vigor gradually enhanced, however, and the electric conductivity of seeds tends to be stable at different date, as to ZD958, at 53 days after pollination, and at 59 days after pollination for XY335, a difference in the electric conductivity of seeds during 1-2 stages of milk line development, however, the difference was disspeared during 3-5 stages of milk line development, and the value of electric conductivity was stable, therefore, the seed had a greatest vigor when milk line was at 3 stage(the milk line is at middle of grain), at 59 days after pollination, and kernel moisture was in 38-40%.