Investigation Of Potato Safety Period Of Plastic Film Mulching In Intensive Agricultural Region Of North China

Crop safety mulching period is the optimal mulching time for specific crops under particular environment.During this period,mulch films were required to be intact and fully functions in maintaining soil temperature or decreasing moisture evaporation.After safety mulching period,the functions of mulch films were no longer highly necessary.In aims of determining the safety mulching period and optimal mulch-uncovering time during potato planting in North China,we performed mulching and mulch-uncovering experiments on potato planting in Jiaozhou and Pingdu during2016²017,with six different treatments:non-mulching?T1?,mulching?T6?,mulch-uncovering after30d?T2?,60d?T3?,75d?T4?,90d?T5?,respectively.By systematically analyzing the effect of different mulch-uncovering time on soil temperature,moisture,potato growth and production,we demonstrate that the optimal removal time of mulch films,as well as safety mulching period of potato planting in North China,is 60⁷5days.Moreover,by taken PE mulch film as control,we carried out field experiment with biodegradable mulch films mainly made of PBAT or PPC on potato planting.Through extensive evaluation on the degradation time of different biodegradable mulch films,and their function on maintaining soil temperature and promoting potato production,we provide that mulch film mainly made of PBAT suited potato production in North China.Our main results were as follows:?1?Function of plastic film mulching on soil moisture and temperature of potato field were mostly obvious in the first 60 days after sowing.During potato sowing and germination,the daily average temperature of 10cm soil under mulching treatment T6 was 13.1¹4.2?,0.8¹.1?higher than bare soil;with the accumulated soil temperature was 369.6?·d,higher than bared soil by 66.1?·d.Comparing to other mulching treatments,mulching films removed at 60 days showed the highest accumulate soil temperature,which is 1793.6?·d.Our result showed that plastic mulch films largely increased the soil temperature in first 60days after sowing,while during 75 to 90 days,mulch films showed little effect.Moreover,our result showed that water use efficiency were the highest(80.2¹13.1 kg?m^-3)when mulch films were removed at 60⁷5d,that is 20.2%⁴0.7%higher than bare lands,and 4.4%¹0.8%higher than non-mulch-removal treatment.?2?Film-uncovering time largely effects potato growth in the intensive farming area of North China.In the early stage of potato growth,film mulching significantly speed up potato seedling growth and shorten potato development process.Comparing to non-mulching field,the time of seedling emergence is 5d earlier,and the growth period is 4d shorter.As that potatoes are thermal-phobic crop,mulch films should be uncovered during the middle and late potato growth stages.Removal of mulch films at 60d after sowing shows highest potato yield,13.4%³1.0%higher than non-mulching field,and4.1%⁸.4%higher than non-mulch-removal treatment.Removal of mulch films at 75d after sowing shows high potato yield,10.4%to 25.9%higher than non-mulching field,and 1.4%to 4.2%higher than non-mulch-removal treatment.Removal of mulch films at 60d after sowing shows highest potato commodity rate,12.8%¹3.0%higher than non-mulching field,and 9.1%¹0.2%higher than non-mulch-removal treatment.Removal of mulch films at 75d after sowing shows high potato yield,11.1%to 11.3%higher than non-mulching field,and 7.4%to 8%higher than non-mulch-removal treatment.Removal of mulch films at 60d after sowing improved potato quality.?3?PBAT biodegradable mulch films performed well in maintaining soil temperature,it begans to break at 65⁷5d,thus avoided harmful effect of high environmental temperature to potatoes.The result of research shows that the yield of potato crop covered by biodegradable film composed of PBAT was the highest,which was 52.5⁵3.3t?hm^-2,which were 6.7%⁸.3%higher than covered by PE film,and 17%¹8.7%higher than non-mulching field.In comparison,biodegradable mulch films composed by PBAT+PPC,or mainly PPC degrades since 35⁵5d,the yield of potatoes was 50.2 to 51 t?hm^-2,far lower than that of PBAT mulching.