Effects of soil potassium levels on dry matter and nutrient accumulation and distribution in cotton

Background Potassium(K)is an essential nutrient for plant growth and development.However,plant fertilization ignoring the soil K level is very likely to cause excessive fertilizer use,and further arouse a series of side effects.This study investigated the response of cotton growth to different soil K levels and the uptake of major nutrients,aiming to evaluate the appropriate K supply level for cotton growth.Using a random block design with 6 soil K levels,we conducted 18 micro-zones field experiments over two continuous years.The soil available K concentration of each treatment was K1(99.77-100.90 mg·kg^(-1)),K2(110.90-111.26 mg·kg^(-1)),K3(123.48-128.88 mg·kg^(-1)),K4(140.13-145.10 mg·kg^(-1)),K5(154.43-155.38 mg·kg^(-1)),and K6(165.77-168.75 mg·kg^(-1)).Cotton nutrient contents,soil nutrient contents,accumulation and distribution of dry matter in cotton were determined,and the relationships between K content in soil and plants and dry matter accumulation were analyzed.Results The soil K content had a significantly positive relationship with dry matter and K accumulation in cotton plants.There were significant differences in dry matter accumulation,single-plant seed cotton yield,mineral nutrient uptake and the proportion of K accumulation in reproductive organs among different soil K levels.The results showed that there was significant difference between K4 and lower K level treatments(K1 and K2),but no significant difference between K4 and higher K level treatments(K5 and K6)in dry matter,single-plant seed cotton yield,or accumulation,distribution and seed cotton production efficiency of N,P and K.Conclusion The soil K level of K4 was able to provide sufficient K for cotton growth in our experiment.Therefore,when the soil K level reached 140.13 mg·kg^(-1),further increasing the soil K concentration no longer had a significant positive effect on cotton growth.

Relationship between Ponkan Mandarin Fruit Quality and Nutrient Concentrations

Five age groups of trees were carried out in order to study relationships between the deterioration of Ponkan mandarin fruit quality and changes in tissues nutrient concentrations with tree age.Fruit quality and nutrient concentrations in fruits and leaves were measured.Comprehensive fruit quality decreased in the order:5-year-old > 13-year-old > 38-year-old > 8-year-old >18-year-old.In 18-year-old trees,calcium(Ca) concentrations of fruit and leaf were lower,while potassium(K) and boron(B) concentrations of fruit and magnesium(Mg) and manganese(Mn) concentrations of leaf were higher.Negative relationships were observed between fruit total soluble solids and leaf B,while positive relationships were observed between fruit total soluble solids and leaf and fruit Ca concentrations,and between titratable acidity and leaf Mn.Fruit quality decreasing with tree age most likely resulted from an imbalance of high K,Mg and B but lower Ca concentrations in leaves and fruits.