Effects Of Controlled-release Urea And Potassium Chloride On Cotton Growth And Soil Fertility In Saline Soil

At present,the controlled-release urea is not only applied on the plants which need less fertilizer,such as lawn and flowers,but also the field crops which need high quantity of fertilizer.Cotton is an important agricultural field crop in China.It is very important to apply controlled-release fertilizer rationally to improve the yield and quality of cotton.In the actual production of agriculture,the blended application of controlled-release urea and uncoated urea reduced the production cost and made the nitrogen release law consistent with the nitrogen absorption law of cotton.However,in addition to the high demand for nitrogen,cotton also has a large demand for potassium.The study of controlled-release potassium chloride as a new type of polmer-coated e potassium fertilizer is few reports in China and in the world.Therefore,the controlled-release potassium chloride and uncoated potassium fertilizer combined with controlled-release urea combined with uncoated urea can play a great role in the actual cotton production and fertilizer utilization.In this paper,by the use of saline soil on Lijin County of Dongying City,Mao Tuo village field,there are three experiments in total.Firstly,in the South Campus of Shandong Agricultural University experimental station,a pot experiment is carried out by comparing different amount of controlled-release urea and controlled-release potassium chloride effects on cotton yield,growth characteristics and soil fertility of the field;Secondly,in Lijin County of Dongying City,Mao Tuo village field,through two years of field experimental study of potassium and nitrogen release characteristics of the controlled-release potassium chloride and urea under field conditions,and different mixing of controlled-release potassium chloride and controlled-release urea fertilizer,in order to find how controlled-release potassium chloride and controlled-release urea fertilizer influence on available cotton yield,fertilizer utilization rate and leaf photosynthetic characteristics of field at the same time;Thirdly,through two years field experiment,conducting to study the effects of different applying methods of different potassium fertilization on cotton yield,leaf senescence,soil potassium and,economic benefits.The main results are as follows:?1?Effects of different dosage of controlled-release nitrogen fertilizers and controlled-release potassium fertilizers on potted cotton yield,physiological characteristics and soil fertilityTo investigate the interacting effects of polymer coated-urea?PCU?and polymer-coated potassium chloride?PCPC?on cotton growth,an experiment was conducted with containerized plants in 2014 and 2015.There were two kinds of nitrogen fertilizer,PCU and urea,which were combined with PCPC at three application rates(40,80 and 120 mg kg^-1 soil).The kinds of nitrogen fertilizer formed the main plot,while individual rates of PCPC were the subplots.The results suggested N and K release patterns for PCU and PCPC in the soil were closely matched to the N and K requirements of cotton.Soil inorganic nitrogen contents significantly increased by using PCU instead of urea,and the same trend was observed with soil available potassium contents,which also had increased rates.Meanwhile,the number of bolls and lint yields of cotton in the PCU treatments were 4.9%-35.3%and 2.9%-40.7%higher than from urea treatments.Lint yields also increased by 9.1%-12.7%with PCPC80 and PCPC120 treatments compared with PCPC40 treatment at the same nitrogen type.Hence,application of PCU combined with 80 mg kg^-1 soil of PCPC fertilizer on cotton increased the yields and fertilizer use efficiencies in addition to improving soil nitrogen and potassium contents.?2?Effects of application of mixtures of controlled-release nitrogen fertilizers and controlled-release potassium fertilizers on yield,photosynthetic traits and fertilizer use efficiencyThe objective of this study was to explore the interaction application effects of polymer-coated potassium chloride?PCPC?and polymer-coated urea?PCU?on cotton yield,fiber qualities,leaf photosynthesis and fertilizer use efficiencies under salinity stressed conditions.A two-year experiment was conducted in two nearby fields with the similar soil fertility but varying salinity,using a split-plot design in the Yellow River Delta area.The main plots were assigned to the types of K fertilizers(K1-180 kg ha^-1 K from potassium sulfate,K2-90 kg ha^-1 K from potassium sulfate+90 kg ha^-1 K from PCPC,K3-54 kg ha^-1 K from potassium sulfate+126 kg ha^-1 K from PCPC,hereafter referred to as 0,50%and 70%PCPC),while the types of N fertilizers(N1-220 kg ha^-1 N from urea,N2-110 kg ha^-1 N from urea+110kg ha^-1 N from PCU,N3-66 kg ha^-1 N from urea+154 kg ha^-1 N from PCU,hereafter referred to as 0,50%and 70%PCU)were assigned to the subplots.The results indicated that the lint yield,number of bolls,boll weight,lint percentage,fiber qualities,leaf photosynthesis and fertilizer use efficiencies were significantly affected by the types of K,N fertilizers and their interaction.The K and N release characteristics of PCPC and PCU under field condition were closely matched to the nutrients requirements of cotton growth.The contents of soil available K and inorganic N were significantly augmented from the first bloom stage to the initial boll-opening stage by using PCPC and PCU compared to potassium sulfate and urea treatments.The combination of 70%PCPC and 50%PCU augmented the cotton fiber properties and photosynthesis properties.Meanwhile,PCPC and PCU interaction increased lint yields by 11.2%-26.4%and 14.2%-32.1%in comparison with potassium sulfate and urea in 2014 and 2015,respectively,and the maximum lint yield was achieved by the combination of 70%PCPC and 50%PCU.Besides,the bolls number and boll weight were improved5.2%-18.2%and 4.8%-10.3%by the PCPC and PCU treatments compared to both potassium sulfate and urea treatments,respectively.The potassium use efficiency?KUE?and nitrogen use efficiency?NUE?of PCPC and PCU treatments were significantly raised by 24.3%-33.8%and 19.7%-36.3%,respectively,compared with potassium sulfate and urea treatments in 2014and 2015.Consequently,the application of 70%PCPC in combination with 50%PCU is recommended to markedly increase cotton yield and fertilizer use efficiency,and to improve the fiber quality and leaf photosynthesis properties on the saline field in the Yellow River Delta area.?3?Effects of different potassium application on cotton yield,leaf senescence,soil potassuim and economic benefitsThe objective of this study was to investigate the effects of polymer-coated potassium chloride?PCPC?fertilization on cotton yields,yield components,fiber qualities,potassium use efficiencies and leaf senescence under saline conditions.A two-year field experiment was conducted on the saline field in the Yellow River Delta of China with a high-yielding cotton cultivar?‘Guoxin 99-1'?.The experiment had the following seven treatments with varying potassium fertilization:70%PCPC mixed with 30%K₂SO₄ applied once before planting?BBF?;PCPC applied once before planting?PCPC?;K₂SO₄ applied twice with first application?40%?before planting and second application?60%?during first bloom stage?KSl?;KCl applied twice with first application?40%?before planting and second application?60%?during first bloom stage?KCl?;K₂SO₄ applied once before planting?KS2?;K₂SO₄ applied once before planting?KC2?;none potassium applied as the control.The release of PCPC appeared to be slow before the squaring stage,but accelerated between the first bloom and boll-setting stages,and then decreased during the late stage including harvest.The BBF treatment improved the cotton fiber properties and photosynthesis properties compared with other potassium fertilizer treatments.The number of cotton bolls was 9.0%-19.7%higher and seed yields was4.4%-28.1%higher,in 70%PCPC mixed with 30%K₂SO₄ treatment than other potassium fertilizer treatments.Also,the potassium use efficiency?KUE?and net profits were increased by 3.4%-40.9%and 5.8%-137.3%,respectively,in the 70%PCPC mixed with 30%K₂SO₄compared with other potassium fertilizer treatments.Available soil potassium contents,fiber qualities and leaf photosynthetic indices were all significantly improved by using PCPC instead of the common potassium fertilizers.The results showed that combining PCPC with K₂SO₄ at a 7:3 potassium ratio can delay leaf senescence,and improve potassium use efficiencies and fiber qualities,and increase yields and economic benefits in cotton.