Objectives Straw mulching combined with strip tillage (“strip tillage”) has been promoted as an effective measurement for black soil protection in Northeast China. In regarding to the exaggerated soil temperature heterogeneity, the adaptability of maize varieties was evaluated, for maintaining maize yield at the same time of soil protection.
Methods Field experiments with split design were conducted in Lishu County, Jilin Province in 2020 and 2021. The main factor was two tillage methods: strip tillage (ST) and conventional tillage (CT), and the sub-factor was 10 maize varieties. The soil temperature of intra- and inter-rows, and the emergence time and rate were monitored, the periodical dry matter accumulation, yield and yield components of maize were investigated. The relative change of indices of maize varieties under ST was calculated using equation (ST–CT)/CT for the adaptive assessment and classification of maize varieties, and their growth dynamics were fitted with logistic equation.
Results Compared with CT, ST treatment decreased soil temperature until 50–70 days after sowing in 2021 and 2022, with the total decrease of cumulative temperature by 305℃ and 107℃ in the intra-rows, and 450℃ and 355℃ in the inter-rows; postponed the emergence time of maize but did not affect the final emergence rate. The yield and yield components of maize varieties responded to the tillage methods differently. Compared to CT, the variety Zhengdan 958, Dika M753, and Dika M751 under ST treatment increased yield by 8.4%, 3.5%, and 2.1%, ranking strong adaptability varieties; Dika 517, Liangyu 99, Fumin 58, Hongshuo 899, and Tieyan 58 reduced yield by 6.6%, 6.0%, 3.3%, 1.5%, and 0.7%, ranking weak adaptability varieties; the left twos ranked moderate adaptability varieties. From the analysis of yield components, the ear number per unit area, the grain number per ear, and the 100-grain weight of high adaptability varieties under ST treatment increased by 1.2%, 4.3%, and 0.5%, respectively, the moderate adaptability varieties decreased by 0.0%, 1.1%, and 2.4%, respectively, and the weak adaptability varieties decreased by 1.7%, 3.9%, and 0.0%, respectively. The logistic growth fitting curve showed that, ST treatment reduced the growth rate of maize from V1 to V14 stage, accelerated the growth rate from V14 to R3 stage, exhibiting the “compensatory growth ability”, and the high adaptability varieties possessed higher compensatory growth ability than the other varieties. The plant average growth rate during the rapid growth period under ST treatment was 6.1% higher than under CT, and the average grain number per ear was 4.3% higher. The correlation analysis showed that the grain yield was positively correlated with the grain number per ear (r=0.65–0.66), the shoot dry weight at maturity stage (r=0.57–0.80), the maximum growth rate (r=0.72–0.84), and the growth rate during rapid growth period (r=0.69–0.83) (P<0.05).
Conclusions Maize varieties are different in the adaptability to strip tillage. Although the low temperature and late emergence caused by strip tillage, the highly adaptive varieties possess stronger "compensatory growth ability" in the rapid growth period, which improves the dry matter accumulation rate in the key growth period before silking stage, promotes the formation of grain number per ear, and finally achieves higher yield.
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