Effects Of Cultivation Pattern On Cotton Yield,Fiber Quality And Nitrogen Use Efficiency At Low And High Soil Fertility

Cultivation pattern and soil fertility have a profound effect on crop production.A two-year experiment was established to investigate the effects of cultivation pattern on the plant growth,seedcotton yield,fiber quality and nitrogen use efficiency at low and high soil fertility levels.The field experiment involved a conventional crop cultivation pattern(Pattern 1)and two crop cultivation patterns(Pattern 2,Pattern 3)was conducted using a widely planted cotton cultivar in the Yangtze River Valley(Siza 3)as plant material in the low and high soil fertility fields at Dafeng,Jiangsu,China(33°19?N,120°45?E)in 2012 and 2013.A nitrogen omission treatment was also included in each field to indicate the soil indigenous N supplies and calculate nitrogen use efficiency traits.The objectives of this study were(1)to explore the physiological mechanism of cultivation pattern effect on cotton yield and fiber quality under cultivation pattern at low and high soil fertility levels through investigating cotton growth and development,boll distribution patterns,and within-canopy fiber quality,and(2)to evaluate the effects of cultivation pattern on cotton nitrogen use efficiency at low and high soil fertility levels by examining the dynamic accumulation of nitrogen and nitrogen allocation in cotton;and(3)to evaluate the differential response of cultivation pattern to soil fertility.The main results were as follows:1.Effect of cultivation pattern on seedcotton yield at low and high soil fertility levelsPattern 1 was used as a reference,Pattern 2 and Pattern 3 enhanced the seedcotton yield in either field,and the yield increment under Pattern 2 and Pattern 3 relative to that was found due to more bolls per unit area.Compared with Pattern 1,the number of bolls on FB1-15 and at FP1-2 on FB16+were elevated under Pattern 2,while the number of bolls on FB1-10 and at FP1-2 on FB11-15 were elevated but the number of bolls on FB16+were reduced under Pattern 3.Interestingly,despite the same cultivation patterns being deployed in the low and high soil fertility fields,higher NAR under integrated crop cultivation pattern relative to that under conventional crop cultivation pattern in the low soil fertility field that brought about the distensible magnitude of seedcotton yield increase for Pattern 2 and Pattern 3 in the low soil fertility field relative to that in the high soil fertility field.2.Effect of cultivation pattern on fiber quality at low and high soil fertility levelsThe fiber quality of bolls with respect to fruiting positions,was not just a function of cultivation but also depended on the mean daily temperature during the period between anthesis and boll open prevailing.Moreover,Pattern 3 achieved superior fiber quality at field level through enhancing the number of bolls on the fruiting branches,where fiber quality is generally superior.The fiber length and strength of bolls on FB1-15 and micronaire of bolls at all fruiting positions was lower than those of Pattern 1,resulting in lower fiber quality under Pattern 2 relative to that under Pattern 1 at field level.The fiber of bolls at FP1-2 on FB1-5 under Pattern 3 was longer and stronger than that of Pattern 1,while the fiber length and strength of bolls on upper fruiting branches(FB11+)and micronaire of bolls at all fruiting positions under Pattern 3 was lower than that under Pattern 1.However,the contribution of bolls on lower fruiting branches(FB1-10)to the total yield under Pattern 3 was lhigher relative to that under Pattern 1,resulting in superior fiber quality at field level under Pattern 3 relative to that under Pattern 1.3.Effect of cultivation pattern on nitrogen use efficiency at low and high soil fertility levelsThe total and reproductive nitrogen accumulation were positively correlated with the seedcotton yield of cultivation pattern.Compare with Pattern 1,the Pattern 2 enhanced nitrogen uptake rate(Vm)and prolonged fast nitrogen accumulation duration(T),while Pattern 3 only enhanced Vm.Though Pattern 2 and Pattern 3 had lower nitrogen harvest index(NHI),they enhanced reproductive nitrogen accumulation due to higher nitrogen content of plant relative to that under Pattern 1.Pattern 2 and Pattern 3 enhanced agronomic nitrogen efficiency(AEN)and recovery nitrogen efficiency(REN).However,physiological nitrogen efficiency(PEN)was significantly affected by soil fertility×cultivation pattern interaction.The PEN under Pattern 2 was lower than that of Pattern 1,but Pattern 3 had no significant difference in.PEN with Pattern 1 in the low soil fertility field;however,the PEN under Pattern 2 and Pattern 3 was lower than that under Pattern 1 in the high soil fertility field.4.The response of cultivation pattern to soil fertilityThe lower boll number per unit area and seedcotton weight per boll was attributed to 16.2%lower seedcotton yield in the low soil fertility field relative to that in the high soil fertility field.There was a diminished yield difference in soil fertility among integrated crop cultivation pattern relative to that of conventional crop cultivation pattern.The difference between conventional crop cultivation pattern and integrated crop cultivation pattern in response to soil fertility were that:(1)the NAR under conventional crop cultivation pattern was significant sigcificantly reduced by decreasing soil fertility,but the NAR under integrated crop cultivation pattern was not sigcificantly changed by soil fertility,(2)the net photosynthesis rate(Pn)of leaves on FB1-5 under Pattern 1 was not significantly changed while the Pn of leaves on FB1-10 under Pattern 2 and Pattern 3 was increased by reducing soil fertility,(3)the number of bolls at FP1-2 on FB1-5 under conventional crop cultivation pattern while the number of bolls on FB1-5 and at FP1-2 on FB6-10 under integrated crop cultivation pattern were not sigcificantly changed by soil fertility.In conclusion,these findings demonstrated that by combining optimal cultivation practices on infertile soils Pattern 3 could minimize the yield differences due to soil fertility,and Pattern 3 could synchronously increase seedcotton yield,fiber quality and nitrogen use efficiency in the infertile fields.The differential of NAR,Pn of leaves on FB1-10 and nunber of bolls on FB1-10 under crop cultivation pattern response to soil fertility brought about the difference between conventional crop cultivation pattern and integrated crop cultivation pattern in response to soil fertility.Moreover,in view of the luxury consumption of nitrogen under integrated crop cultivation pattern and the lower yield increasing rate of integrated crop cultivation pattern over conventional crop cultivation pattern in the high soil fertility field,we recommended that the integrated crop cultivation pattern,which applied in the fertile fields,should integrate other cultivation practice except fertilizer to achieve the full potential of cotton varieties.