| Calcium(Ca)fertilizer application is not common in potato production in China,and even in soils with high Ca content,physiological Ca deficiencies in potato tubers could be found for Ca absorption problems.Potato tubers are usually stored fresh,then the high water content and the ongoing metabolism lead to their high susceptibility to be rot,black heart,sprouting and loss of nutrition value during storage.Therefore,in order to improve the quality and storability of potato tubers to reduce tuber losses and quality loss during storage,the effects of different Ca applications rate on potato tuber yield,quality and storability were conducted by field trials in this study.It was expected to provide theoretical and practical references for the rational use of Ca fertilizer in potato production through a comprehensive evaluation of the indicators.The experiment was conducted in 2021-2022 in BeiLin District,SuiHua City,Heilongjiang Province,the early-maturing variety’Youjin’was used as the test material and five treatments with a series of CaO rates,0(CK),20(Ca20),40(Ca40),60(Ca60)and 80(Ca80)kg/hm~2were set,the following conclusions were drawn from the measurement and analysis of the various indicators of the plant or tuber data:(1)Ca could promote the growth and development of potato plants and improve metabolism:potato plants treated with Ca had a higher height and stem thickness at seedling stage,while Ca60treatment’s were significantly higher than CK treatment(p<0.05);leaf chlorophyll content reached its maximum at tuber formation stage for all treatments and CaO rate of 40-60 kg/hm~2was significantly higher than other treatments(p<0.05);The leaf malondialdehyde(MDA)content gradually increased with the growing period and tended to be a’S’curve with the increase of Ca application,Ca60 treatment had the lowest value and decrease of 1.88%and 27.25%(p<0.05)compared to CK in two years.Ca not only favoured dry matter accumulation in above-ground,but also promoted translocation of dry matter to tubers(p<0.05).Two-year trial showed that the Ca60treatment had 192.79 and 192.32 g/plant of tuber dry matter at harvest time,which were significantly higher than that of CK(p<0.05).(2)Application of Ca could increase Ca accumulation in all potato organs:The characteristic of Ca accumulation in leaves,above-ground stems and the whole potato plant was’S’curve,and reached the maximum during tuber expansion.but the Ca accumulation and allocation ratio in tubers increased gradually all the time.Because Ca stored in the stems and leaves couldn’t be transferred to tubers,the above-ground stems and leaves are therefore the main calcium accumulating organs.The results of the two-year trial showed that Ca accumulated in tubers at harvest in the Ca60 treatment was 6.29(2021)and 7.23 kg/hm~2(2022),with an increase of 86.79%and 110.14%compared to the CK(p<0.05).(3)Ca could improves the physicochemical properties of potato starch:Amylopectin content,starch transparency and swelling capacity of potato starch increased and then decrease with Ca rate increased.All items mentioned above reached the maximum at Ca60 treatment(except for starch transparency in 2021)which increased by 8.70%,23.92%and 8.72%over CK in both years(p<0.05)in average.In contrast,amylose content and starch solubility decreased and then increased,while Ca60 treatment decreased by 13.20%and 27.21%respectively compared to CK(p<0.05).(4)Ca could slow down the reduction of stored potato tubers quality:Before storage,tuber starch,vitamin C(Vc),soluble protein and dry matter contents of Ca60 treatment were 10.83%,26.74%,44.01%,8.93%and 26.88%,45.28%,65.82%,6.32%higher than CK for two years,respectively(p<0.05),while reducing sugar,nitrate and MDA contents of tubers of Ca60treatment reduced by 29.64%,15.49%,40.99%and 36.00%,17.86%,29.28%compared with CK respectively(p<0.05).After storage,tuber starch content,Vc,soluble protein and dry matter contents of Ca60 treatment were 19.73%,24.39%,58.30%,17.13%and 61.51%,63.57%,76.81%15.47%higher than CK respectively(p<0.05),and reducing sugars,nitrate and MDA contents of tubers of Ca60 treatment were reduced by 50.73%,23.52%,49.83%and 57.05%,24.33%31.90%than CK respectively(p<0.05).Compared to the CK treatment,the decrease of starch,Vc and dry matter content and the increase of reducing sugars,nitrate and MDA content were all significantly lower in the Ca60 treatment during storage.(5)Ca application could increases the yield of commercial potato tubers:Ca application could significantly increase the commercial tuber ratio and average potato weight(p<0.05)but reduced the number of potato per plant.For the treatments with CaO of 40-60 kg/hm~2,the two-year average commercial tuber ratio was increased by 3.51%-4.81%(p<0.05)and the average tuber weight was increased by 21.14%-26.98%(p<0.05)compared with CK.(6)Application of Ca could reduces the storage loss of potato tubers:Compared to the CK treatment,the Ca60 treated tubers showed a two-year average reduction of moisture loss,weight loss,weight decay and quantity decay rates after 90-day storage were 19.57%,50.32%,95.66%and 83.71%respectively(p<0.05).(7)Application of Ca could increase the hardness of potato tubers and the skin thickne ss:Two-year the tuber hardness of Ca60 treatment was 7.66%-11.20%(with skin)and 14.25%-16.91%(without skin)(p<0.05)higher than CK,and the thickness of potato skin was47.55%-72.27%(p<0.05)higher than CK.In conclusion,under the conditions of this experiment,combining the effects of calcium on potato tuber yield,quality and storability,the recommended application rate of CaO is 38-42kg/hm~2if yield is the main objective,and 50-70 kg/hm~2if improving tuber quality and storability is the main objective. |
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