Study On The Cultivation Techniques Of Sweet Sorghum In The Saline Soil Of Yellow River Delta

The experiments were conducted both in the lab and out in the field. In lab experiment wetreated sweet sorghum JZ1with different NaCl concentrations (0mmol·L^-1,50mmol·L^-1,100mmol·L^-1,150mmol·L^-1and200mmol·L^-1) and different nutrient components in order toelucidate the effect of salt stress on the growth status of sweet sorghum, and to develop theoptimum formula for sweet sorghum cultivation in saline condition. In field experiment, on theother hand, we planted several sweet sorghum cultivars in the saline soil of Yellow River Deltawith a salinity of about0.3%⁰.6%, in order to screen the sweet sorghum candidate forbio-ethanol production in saline soil, Further more, we explored the effect of different sowingtime and different cultivation measures on the yield and other biological traits of sweet sorghumin order to develop practical cultivation techniques of sweet sorghum in the saline soils of YellowDelta. And the results are as follows:1lab experiments1.1Effect of different NaCl concentration on the growth of sweet sorghumUnder NaCl treatment, the growth of sweet sorghum was seriously inhibited, with the freshweight, dry weigh and leaf area all decreased with the NaCl concentration. Furthermore, the leafmembrane permeability and MDA content increased with NaCl concentration. On the other hand,due to the restriction of stomatal factors, The net photosynthetic rate decreased with the increaseof NaCl concentration, with the photosynthetic apparatus being also damaged, the primaryphotochemical reactions was inhibited, the excited energy was forced to be dissipated bynon-photochemical dispassion in order to protect the photosystems. As for the ion accumulation,Na⁺was mainly detained in the root while K⁺was allocated in the leaves for osmotic adjustment.In our experiment, slight salt stress lower than50mmol·L^-1NaCl only slightly affect sweetsorghum, yet NaCl of more than50mmol·L^-1significantly reduced the biomass andphotosynthetic rate, suggesting sweet sorghum is moderately salt-tolerant.1.2Effect of different nutrient components on the growth of sweet sorghum Under different nutrient component treatment, the growth of sweet sorghum was affected.With the increase of nitrogen and phosphor level, the height, leaf area, fresh weight and dryweight of sweet sorghum also increased. However, under certain nitrogen and phosphor level,the growth of sweet sorghum decreased with potassium level. Under NaCl treatment, the growthof sweet sorghum can be promoted by nitrogen, phosphor and potassium supplied in suitableamount. Under saline conditions, a formula of5mmol·L^-1nitrogen,1mmol·L^-1phosphor and3mmol·L^-1potassium was optimum for the growth of sweet sorghum, in the economical andbiological considerations.2Field experimentsWith the fast development of world economy, the society is more and more dependent onenergy. As fossil fuel is over exploited in the recent decades, the crisis of energy shortage isexacerbated. Since the fossil fuels such as petroleum and coal are not renewable, we are forcedto search for other renewable energy resources. One of them is biomass energy. Biomass isbiological material derived from living, or recently living organisms, thus biomass energy is totransform the substances contained in plants into biomass fuel such as ethanol. This strategy isnow world widely adopted, so is in China. With high sugar content, sweet sorghum is an idealcrop to produce fuel alcohol. Saline soil is widely distributed all over our country. Just in YellowRiver Delta of Shandong Province, an estimated6000hm²saline soil increases every year. Theproduction of sweet sorghum in this region can make the best of saline soil to develop newbiomass energy without occupation of cultivation land. For this reason, we conducted fieldexperiments to screen optimum sweet sorghum cultivar and develop practical cultivationtechniques in Yellow River Delta.2.1Experiments with different cultivarsWe planted8sweet sorghum cultivars in the Qingtuo Farm of Yellow River Delta. LSZ1owed the highest kernel weight and ear weight, but it was low in stalk height and stalk yield.Besides, it was easy for it to catch a disease and lodges slightly, so it is not proper for it to be anenergy crop candidate. On the other hand, LT1, LT3and LT6all had high stalk yield and earyield, they tended to lodge and had long growth period, and are thus also not proper to be thecandidates. JZ1, JZ2, JZ3and JZ4all had high stalk and ear yield and similar growth period, yetJZ3was not lodging-resistant and JZ4had low Brix content, leaving only JZ1and JZ2being thebest energy crop candidates.2.2Experiment of different sowing timeWe selected JZ2as the experiment cultivar and sowed it mechanically on May12, May27,June12and June27respectively, each separately by half a month （a solar term） interval. And then its influence on the yield, sugar content, juice content and other agronomy characters wasstudied. The results that the stalk height and yields of the sorghum sowed on May27and June12were higher than the others. The sugar content, juice content of the sorghums sowed on May12,May27and June12showed no significant difference. However, the sweet sorghum sowed onJune27, being restricted by the relatively low temperature at the second half period of its growth,had low sugar content and kernel weight as well as ear yield.As an energy crop, the most relevant traits to sweet sorghum are stalk yield, juice contentand Brix content, thus the best sowing time for sweet sorghum in Yellow River Delta would belate May to Early June.2.3Experiments with different cultivation measuresThe soil of Yellow River Delta is lack of nitrogen and phosphor nutrients as well as organicmatter; however, it is very high in salt content. Soil salinity moves as the water moves in the soil.In early spring, soil salt content is low, however, as the temperature rises with the relatively lowprecipitation, soil salt content increases rapidly in middle and late spring; then decreases whenthe rainy season comes in summer. After the rainfall season, the soil salt content increasesafterwards.Based on the pattern of water and salt movement in the saline soil of Yellow River Delta,we conducted several field experiments such as density experiment, plastic film mulchingexperiment, organic manure experiment and addition fertilizer applying experiment. By theseexperiments we developed a set of practical cultivation measures suitable for saline soils. Beforesowing, the fields should be flooding irrigated to reduce the salt content in the surface layer.Plenty of basic fertilizer should be applied in the fields, mainly organic fertilizer,100¹50Kg/mu, and a small amount of DAP （diammonium phosphate） about20Kg/mu to supply theNitrogen and phosphor. Then the sweet sorghum should be sown timely. The suitable linespacing is45cm. Plastic film mulching was suggested after sowing, which can effectively keepwater, reduce soil content and increase soil temperature. Furthermore, it can increase the numberof soil microorganism and promote seedling emergence while shorten the growth period.Additional potassium leaf fertilizer was suggested during the heading period and grain fillingperiod, which can increase yield, juice content and Brix content.