Effects of vertically rotary sub-soiling on nutrient and water utilization and tuber yield of potato in semi-arid area of northwest China

Objectives The vertically rotary sub-soiling is effective to improve soil capacity of water supplying and promote the crop root development, this is probably beneficial to the nutrient availability for crop uptake.

Methods The field experiments were conducted for three years (2016–2018) in Gansu Province, using potato as test material. The involved tillage treatments were vertically rotary sub-soiling for 40 cm (VRT), sub-soiling for 40 cm (SS), and traditional tillage for 15 cm (TT), all the treatment plots were mulched by plastic film annually. The soil water, soil available nitrogen (AN), available phosphorous (AP), readily available potassium (AK) content were measured at sowing, before flowering and at maturing stage of potato. The SPAD value and leaf area index (LAI) of potato were measured during flowering stage, and the tuber yield was investigated at maturity; the periodic evapotranspiration (PET), periodic nutrient consumption (PNC), and water use efficiency (WUE), nutrient use efficiency (NUE) were calculated.

Results VRT method increased soil water storage at sowing stage in 0–120 cm profile, increased the AN and AP contents in 0–40 cm profile, as compared with SS and TT treatments. The water consumption before flowering period were significantly higher in VRT treatment throughout from 2016 to 2018, and that in post-flowering period was significantly higher in 2016 (drought year), but not significantly different in 2017 and 2018 (normal and wet year), as compared with SS and TT treatments. More soil AN was consumed in VRT treatment than SS and TT treatments, the consumption differences with SS and TT in pre- and post-flowering period were 38.7, 25.9 kg/hm² and 25.9, 12.9 kg/hm² in 2016 (drought year), 17.2, 0.4 kg/hm² and 21.2, 6.3 kg/hm² in 2017 (normal year), and 13.6, 4.1 kg/hm² and 26.8, 2.8 kg/hm² in 2018 (wet year), respectively. Correspondingly, the consumption of AP and AK in pre- and post-flowering period had also been increased in VRT treatment. LAI in VRT treatment were significantly higher than those in SS and TT treatments. The tuber yield of potato in VRT treatment was increased by 156.8% and 47.8% in 2016, 24.8% and 41.0% in 2017, and 19.6% and 27.5% in 2018, as compared with SS and TT treatments, respectively. The use efficiency of water, N, P and K were increased in VRT, and the significant differences were observed in drought and normal year.

Conclusions The VRT method could increase the water storage of 0–120 cm soil layer and the contents of available N and available P in 0–40 cm soil profile, which is good for the water and nutrient supply to potato, especially in pre-flowering stage, and the vegetation growth (higher SPAD and LAI values), thus obtain high tuber yield and water and nutrient efficiency of potato. In addition, VRT method is found optimized soil water and nutrient distribution, which alleviates the down movement of nutrient, this effect is more remarkable in drought year.