Effect Of Rhizosphere Aeration On Growth And Its Physiological Mechanism Of Muskmelon And Tomato

For the crop, traditional irrigation provides moisture while driving hypoxia stress on roots. Irrigation in heavy clay soil or under unreasonable management will worsen the anoxic condition of the soil.If the root stays in the anaerobic environment or cannot get enough oxygen for a long time, it would be declined for the water and nutrients absorption of root. Also, it will change the hormone levels and enzyme activities of the plant, block the photosynthesis, limit the function of vegetative organs, and eventually lead to the decline of crop yield and quality. Artificial aeration has been shown to promote rootmetabolism and growth, also it enhanced nutrient absorption and soil redoxase enzyme activity as well as accelerated thegrowth and yield of vegetables.In this context,air was injected into the soil through the buried dripirrigation tubes with an air compressor. Some studies used field and potted experiments to explore the effects of soil aeration frequency, aeration volume, irrigationamount, depths ofsubsurfacedripirrigation and NaCl salinity levels on soil enzyme activity, microbial abundance, plant growth, photosynthesis, yields and fruit quality of tomato and muskmelon. Information on how themuskmelon and tomato plant roots adapt to the soil aeration wouldprovide guidance for field production practices as well as indications of possible mechanisms for the observed responses.Someconclusions are as follows:(1) Soil aeration can ameliorate hypoxia stress and overcome the negative effects of poor soil aeration, promote the plant growth and increase fruit yield.Aeration was suggested to be applied once a day and lateral depths of subsurface drip irrigation was 25 cm,which have positive impact on muskmelon yield, quality(total soluble solids, soluble protein, titratable acid, soluble sugarand vitamin C content), fruit shape(fruit length, diameter and flesh thickness) and irrigation water use efficiency. With a 40-cm burial of drip irrigation tubes, 1.5 times the standard aeration volume produced the highest first-picked tomato fruit yield, which was increased by 135.5% relative to the control group. Meanwhile, with a 15-cm burial, the standard aeration volume produced the highest first-picked tomato fruit yield, which was increased by 75.1% compared with the treatment without aeration.Soil aeration alsopromote the plant growth and increase fruit yield under NaClstress condition.(2) The activity of soil enzymes are positively correlated withnutrient cycling and water use efficiency. Aerationhadasignificant impact onrhizosphere soil enzyme(urease, phosphatase and catalase) activitiesandrhizosphere soil microbial(bacteria, fungi and actinomycetes) quantity.Aeration treatment can also enhance the activities of non-rhizosphere soil enzymes, but it has a smaller effect on these activities than on rhizosphere soil enzyme activity.Formuskmelon, the optimal lateral depth of subsurface drip irrigation was25 cm. Thegreatest ureaseactivitiesand bacteriaamountscouldbeobtainedthroughaeratingonceaday, it led to an increase of 28% and 74% compared with the unaerated control.The greatest catalase activities and fungi amounts could be obtained through aerating once every two days, It led to an increaseof 6% and 200% compared with the unaerated control.Aerating once every four days led to an increase in the actinomycetes of 3% compared with the unaerated control.(3) Drip tubing placement, supplemental soil aeration frequency,and irrigation level affected total length, surface area, volume, forks and activityof greenhouse-produced, subsurface drip-irrigated muskmelonroot systems. The effect was more marked for the <1 mm diameter roots. Aerating onceaday increased thetotal root length, surface area and volume by 83%, 63% and 54%, respectively, compared with the no aeration treatment. Nevertheless, higher soil aeration frequencyreduce theroot forks.(4) Soil aeration can promote the growth, and increase the dry matter accumulation of potted single tomato plants, thus promoting fruit yields. There was a positive correlation between dry matter accumulation, net photosynthetic rateand chlorophyll content. This may caused by the relationship between the influence of plant root zone aeration and plant biosynthesis of ABA(abscisic acid).Afavourablesoil gas environment reduces ABA synthesis.There was a positive correlation between ABA and stomatalresistance. Thegreatest leaf area index, chlorophyll content, net photosynthetic rate anddry matter accumulationcouldbeobtainedthroughaeratingonceaday. Net photosynthetic rate and chlorophyll content was higher for the 10-cm burial of drip irrigation tubes aeration during the earlier growth stages. NeverthelessThe optimal lateral depth of subsurface drip irrigation for higher net photosynthetic rate and chlorophyll content was 40 cm. Results showed that drip tubing placement and artificial aeration treatments significantly affected photosynthetic characteristics, chlorophyll content and dry matter accumulationof greenhouse tomato.Net photosynthetic rate increased by 21.4% and 65.0% at 15 and 40 cm depth of the tube.The changing trend of Chlorophyll a, dry matter accumulation and fruit yields of tomato rate showed the first increase and then the decrease with the increase of aeration volume at 15 cm depth of the tube.These parameters increased by 38.0%, 55.4%, and 59.0%, respectively, in the standard aeration volumecompared with the no-aeration.However, chlorophyll a, dry matter accumulation and fruit yields of tomato showed increased with increasing volume of aeration at 40 cm depth of the tube, these parameters increased by 33.7%, 36.2%, and 105.4%, respectively, in the 1.5 times standard aeration volumecompared with the no-aeration.(5) based on production, quality and water use efficiency, aerating once a day,lateral depth was 25 cm and 70 field capacity would be the most appropriate treatment combination for starting irrigationgrows of muskmelon in plastic greenhouse.Meanwhile, with a 40-cm burial, the standard aeration volume and 1.5 times the standard aeration volume had the highest tomato fruit yield, the highest economic benefits were obtained from the standard aeration volume treatment.Under the lower salt stress(Na~+?29mM), soil aeration could effectivelyoverwhelmed the harm from salt stress. Soil aeration can lessen the damage frommedium salt stress(75mM Na~+), andsoil aeration can effectively reduce thedeath rate of potted tomato underhigh salinity stresscondition(121mMNa~+).