Water And Fertilizer Retention Characteristic Of Camellia Oleifera Shell-based Water-retaining Material And The Effect Of Its Application On Camellia Oleifera Seedings

The seasonal drought is one of the limiting factors for the efficient development of forestry in Jiangxi province,but the drought-resistant and water-saving measures adopted at the present stage are relatively limited.Therefore,it is considered to improve the water-retaining material by using forest wastes in situ to reduce water loss,which provides a new idea for guaranteeing the soil moisture of forest land.Camellia oleifera is one of the main economic tree species for farmers in mountainous areas of Jiangxi province to shake off poverty and become prosperous.There are more than 1 million hectares of C.oleifera cultivation area in Jiangxi province,and the average annual yield of fruit is about 540,000 tons.But the fruiting period of C.oleifera overlaps with the seasonal drought in C.oleifera producing areas,which affects the yield of C.oleifera,and thus is not conducive to the stable development of C.oleifera industry.Moreover there are 300,000 tons discarded C.oleifera shells in the processing of camellia oil.Usually the C.oleifera shells will be discarded directly,but this will cause environmental pollution.However,C.oleifera has many excellent characteristics,such as developed structure,abundant cellulose,and its biochar has high porosity.These excellent properties make it suitable for the preparation of water-retaining materials.Therefore,It is of great significance to use C.oleifera shell and biochar to prepare composite water-retaining materials and apply them in production practice,which can alleviate the short-term water shortage in C.oleifera forest land,improve the efficiency of agricultural and forestry waste treatment and promote the development of water-saving forestry in Jiangxi province.In this study,polyacrylamide was modified with C.oleifera shell and biochar respectively by solution blending method to prepare C.oleifera shell composite waterretaining materials and biochar composite water-retaining materials.In addition,the properties of two kinds of self-made composite water-retaining materials and polyacrylamide under different fertilization conditions were tested by indoor simulation test,and the effects on the growth of C.oleifera seedlings were explored through pot experiment,so as to find the most suitable water-retaining material for C.oleifera forest in red soil area of Jiangxi province.The main results are as follows:(1)The treatments of water-retaining materials could improve soil saturated water content,slow down soil water evaporation and put off the end time of evaporation.Among them,the soil saturated moisture content was positively correlated with the amount of water-retaining material applied,while the moisture evaporation was negatively correlated with the amount of water retaining material applied.Under the condition of no fertilization,the saturated water content of soil with 0.4%polyacrylamide was significantly increased by 13.99%,and the evaporation rate was the slowest.After fertilization,the saturated water content of soil with 4%C.oleifera shell composite water-retaining material increased significantly by 18.93%～19.88%compared with the control group,and the effect of slowing evaporation was outstanding and the water-retaining performance was good.(2)Different treatments of water-retaining materials could inhibit the leaching of nitrogen and phosphorus in soil.Among the three water-retaining materials,the composite water-retaining materials of C.oleifera shell had the best inhibiting effect,and the inhibiting effect was more significant with the increase of application amount.Besides,the leaching rate range of nitrogen and phosphorus respectively were 0.59%～1%and 0.87%～1.97%.(3)The pot experiment showed that different water retaining materials had different effects on the growth of C.oleifera seedlings.Among them,the seedlings treated with the biochar composite water-retaining material had better growth situation on the whole,and when the dosage was 1%,its seedling growth was best.After that,with the increase of the dosage,the growth rate of seedling plant height and biomass slowed down.However,the biochar composite water-retaining material had no significant effect on seedling diameter growth rate.In addition,the effects of three water-retaining materials on the contents of available nitrogen and phosphorus nutrient in potted soil were different.Under the condition of no fertilization,the content of ammonium nitrogen in potted soil increased by 4.8%～100.97%with the treatment of water-retaining materials.As for content of nitrate nitrogen,polyacrylamide also had a cumulative effect on soil nitrate nitrogen,but the composite water-retaining material of C.oleifera shell had been inhibiting effect.Moreover,the accumulation effect of soil available phosphorus was not significantly affected by the treatment of water-retaining materials.To sum up,the three water-retaining materials all had the effect of water-retaining and fertilizer retaining.Among them,under the condition of no fertilization,the effect of water and fertilizer preservation of polyacrylamide was better,and after fertilization,the effect of water and fertilizer preservation of C.oleifera shell composite material was more prominent.However,the red soil has heavy viscosity,and excessive soil water content will lead to the imbalance of water-air ratio in the soil,which is not conducive to plant growth.Therefore,the comprehensive measurement results showed that the biochar composite water-retaining material was more suitable for the application of C.oleifera forest in red soil area and its low cost make it easy to promote.