In China, there is an increasing need for greater genetic diversity in maize (Zea mays L.) germplasm and hybrids appropriate for mechanical harvesting. In order to test and distinguish American maize inbred lines with exceptional combining ability, four Chinese maize inbred lines (Chang7-2, Zheng 58, four-144 and four-287) were used to judge the combining ability and heterosis of 16 USA inbred lines by a NCII genetic mating method. The results showed that among the American inbred lines, 6M502A, LH208, NL001, LH212Ht, PHW51, FBLA and LH181 expressed good GCA for yield characteristics; while RS710, PHP76, FBLA, and PHJ89 showed excellent GCA for machine harvesting characteristics. Five hybrids (NL001 × Chang7-2, LH212Ht × Chang7-2, FBLA × four-144, LH181 × four-287, PHK93 × four-287) had better SCA values for yield characteristics, at 1.69, 1.07, 1.48, 1.84 and 1.05, respectively; while NL001 × Chang 7-2, 6M502A × Chang7-2, LH212Ht × Chang7-2, LH181 × four-287, PHW51 × Chang7-2 had better TCA values for yield characteristics, at 3.03, 2.80, 2.41, 2.19 and 1.91, respectively; NL001 × Chang7-2, 6M502A × Chang7-2, LH212Ht × Chang7-2, LH181 × four-287, PHW51 × Chang7-2 showed excellent Control Heterosis values, with 21.48%, 19.64%, 15.93%, 14.05% and 11.60% increases, respectively, compared to the check and potential for future utilization in Inner Mongolian corn production.

Crop yield losses have escalated worldwide due to extreme and/or prolonged drought periods as well as insufficient irrigation. In the cold and arid regions of northern China, the difficulty of straw decomposition is a regional problem, which is undoubtedly aggravated by the increasingly serious drought. Thus, the combination of a reasonable grain feed rotation mode and tillage mode of straw returning is an effective measure to solve this problem. This study set up a grain forage rotation (in the first year, it is used for grain production, and the straw is returned to the field after the grains are harvested; when the entire plant is harvested in the second year, it is used as feed) and two treatments for straw returning and no straw returning to the land characterized by two different water degresses (include drought stress and normal irrigation). To clarify the impact of returning straw to the field on the soil improvement and drought tolerance of various maize varieties, the effects of straw returning on the agronomic traits, hormones, osmotic adjustment substance content, whole plant fresh weight, and dry weight of six different maize varieties (MC703, A2636, DK 159, ZQ 1, 303 × 178, and ZJ 330) under drought stress were analyzed. The data showed the following: (1) After straw returning, the soil moisture content increased by 3.55–14.70% and the soil bulk density decreased by 0.73–5.23% under the drought stress treatment, and the soil physical condition became closer to the ideal value. (2) After straw returning, the plant height, ear height, stem diameter, fresh weight, and dry weight of the maize whole plant under the drought stress treatment increased by 0.95–7.70%, 4.70–15.71%, 0.31–9.33%, 2.67–36.23%, and 3.72–38.60%, respectively. (3) After straw returning, the abscisic acid, ethylene, soluble sugar, and soluble protein in the leaves under the drought stress treatment decreased by 7.92–21.42%, 8.03–3.37%, 0.63–22.98%, and 2.37–9.17%, respectively. Straw returning significantly alleviated the damage caused by drought stress to the growth and development of maize, and promoted the growth and development of maize under the drought treatment. The results of this study provide a theoretical basis for a high and stable yield of grain crops in arid areas.

In China, there is an increasing need for greater genetic diversity in maize (Zea mays L.) germplasm and hybrids appropriate for mechanical harvesting. In order to test and distinguish American maize inbred lines with exceptional combining ability, four Chinese maize inbred lines (Chang7-2, Zheng 58, four-144 and four-287) were used to judge the combining ability and heterosis of 16 USA inbred lines by a NCII genetic mating method. The results showed that among the American inbred lines, 6M502A, LH208, NL001, LH212Ht, PHW51, FBLA and LH181 expressed good GCA for yield characteristics; while RS710, PHP76, FBLA, and PHJ89 showed excellent GCA for machine harvesting characteristics. Five hybrids (NL001 × Chang7-2, LH212Ht × Chang7-2, FBLA × four-144, LH181 × four-287, PHK93 × four-287) had better SCA values for yield characteristics, at 1.69, 1.07, 1.48, 1.84 and 1.05, respectively; while NL001 × Chang 7-2, 6M502A × Chang7-2, LH212Ht × Chang7-2, LH181 × four-287, PHW51 × Chang7-2 had better TCA values for yield characteristics, at 3.03, 2.80, 2.41, 2.19 and 1.91, respectively; NL001 × Chang7-2, 6M502A × Chang7-2, LH212Ht × Chang7-2, LH181 × four-287, PHW51 × Chang7-2 showed excellent Control Heterosis values, with 21.48%, 19.64%, 15.93%, 14.05% and 11.60% increases, respectively, compared to the check and potential for future utilization in Inner Mongolian corn production.