Effect of K Fertilizer on Absorption of Mineral Elements in Greenhouse-grown Strawberry Fruits

[Objectives]The paper was to explore the effect of K fertilizer on the absorption of mineral elements in greenhouse-grown strawberry fruits.[Methods]A systematic investigation was conducted on the effects of K fertilizer dosage levels on the absorption of mineral elements in Fengxiang strawberries,an excellent variety suitable for cultivation in Anhui Province.The investigation was carried out under medium N and P conditions in a greenhouse.[Results]The N content of strawberry fruits increased as the K_(2)O dosage increased within the range of 0-250 kg/hm^(2).Similarly,the P content of strawberry fruits increased gradually with the increase of K_(2)O dosage within the range of 0-125 kg/hm^(2).[Conclusions]This study presents a basis for enhancing the absorption of mineral elements in strawberry fruit by applying K appropriately.

High variation of fungal communities and associated potential plant pathogens induced by long-term addition of N fertilizers rather than P, K fertilizers: A case study in a Mollisol field

Nitrogen(N),phosphate(P),and potassium(K)are the three most important nutrients applied into agricultural soils,but the impacts of their single or combined application on soil fungal community structure and stability are still open questions.Using qPCR and Illumina Miseq sequencing,the variation of soil fungal communities in response to long-term addition of N,P,or K fertilization alone and their combinations in a Mollisol field was investigated in this study.In addition,the fungal community resistance indices and network structure were studied.Results showed that N fertilizations(N,NK,NP and NPK treatments)rather than P,K fertilizations(P,K and PK treatments)significantly increased fungal abundance,but decreased fungal diversity and shifted fungal community structures when compared to non-fertilization(NoF).Additionally,N fertilization treatments presented lower resistance of fungal communities to environment disturbances than those of P,K fertilization treatments.More numbers and higher abundances of changed fungal taxa at the genus and OTU levels were induced by N fertilizations rather than by addition of P,K fertilizers.In addition,N fertilizations induced a more changeable fungal network and complex pathogenic subnetwork with many positive interactions among responding plant pathogens(RP,the changeable plant pathogens induced by fertilizers addition compared to NoF)when compared to P,K fertilizations.These RP directly and negatively influenced fungal community resistance examined by structural equation modeling(SEM),which were indirectly detrimental to soybean yields.Our findings revealed that addition of N fertilizers significantly disturbed fungal communities and promoted pathogenic interactions,and provided insights into the optimization of fertilization strategies toward agricultural sustainability.

Effect of Long-Term Application of K Fertilizer and Wheat Straw to Soil on Crop Yield and Soil K Under Different Planting Systems

Effect of application of K fertilizer and wheat straw to soil on crop yield and status of soil K in the plough layer under different planting systems was studied. The experiments on long-term application of K fertilizer and wheat straw to soil in Hebei fluvo aquic soil and Shanxi brown soil in northern China were begun in 1992. The results showed that K fertilizer and straw could improve the yields of wheat and maize with the order of NPK ＋ St 〉 NPK 〉 NP ＋ St 〉 NP, and treatment of K fertilizer made a significant difference to NP, and the efficiency of K fertilizer in maize was higher than in wheat under rotation system of Hebei. In contrast with Shanxi, the wastage of soil potassium was a more serious issue in the rotation system in Hebei, only treatment of NPK ＋ St showed a surplus of potassium and the others showed a wane. K fertilizer and straw could improve the content of water-soluble K, nonspecifically adsorbed K, non-exchangeable K, mineral K, and total K in contrast to NP; however, K fertilizer and straw reduce the proportion of mineral K and improve proportion of other forms of potassium in the two locating sites. Compared with the beginning of orientation, temporal variability character of soil K content and proportion showed a difference between the two soil types; furthermore, there was a decrease in the content of mineral K and total K simultaneously in the two locating sites. As a whole, the effect of K fertilizer applied to soil directly excelled to wheat straw to soil. Wheat straw to soil was an effective measure to complement potassium to increase crop yield and retard the decrease of soil K.

Straw return increases crop grain yields and K-use efficiency under a maize-rice cropping system

Straw return is an effective way to improve crop grain yield and potassium(K)use efficiency by increasing soil K content.However,the effects of straw return on soil K supplying capacity,replacement of K fertilizer,and K-use efficiency under maize(Zea mays L.)–rice(Oryza sativa L.)cropping systems are little studied.A two-year field experiment was conducted to determine the physiological determinants of K-use efficiency under straw return with four K fertilization rates.Sr33(straw returned plus 33%of K fertilizer applied)and Sr67(straw returned plus 67%of K fertilizer applied)increased annual crop yields by 1.5%and 3.2%and increased agronomic K-use efficiency by respectively 2.9 and 1.3-fold on average in the two years,compared with the conventional practice S0K100(no straw returned plus normal amounts of K fertilizer applied).The Sr33 and Sr67 treatments resulted in significantly greater equilibrium K concentration ratios(CR0 K)and specifically exchangeable K(KX)values according to quantity/intensity(Q/I)relationship analyses,indicating improvement of the potential soil K supply capacity.However,the Sr67 better maintained the soil exchangeable K level and K balance.The results suggested that K released from maize and rice straw can replace about half of chemical K fertilizer,depending on the available K content in maize–rice cropping system production.

Regional Evaluation of Winter Rapeseed Response to K Fertilization, K Use Efficiency, and Critical Level of Soil K in the Yangtze River Valley

The investigation was carried out to study the response of winter rapeseed to potassium （K） feritlization and the critical soil available K level for current winter rapeseed production in the Yangtze River Valley （YRV） of China. A total of 132 field experiments were conducted in fields of farmers in the major winter rapeseed growing areas in YRV in 2000/2001 and 2004/2005 to 2006/2007 during growing season. Results of these field experiments showed that the average rapeseed yield increment resulting from 100 kg K ha-1 application was 358 kg ha-1, an increase over the control CK （no K） of 18.0% in 2005/2006 and 2006/2007. The average internal use efficiency （IE） of K was higher in the CK treatment （21.9 kg grain, kg-1 K uptake） than in the ＋K （100 kg K ha-1） treatment （17.7 kg grain, kg-1 K uptake）. Winter rapeseed required 68.1 kg of K to produce 1 000 kg seed. The recovery efficiency of K fertilizer in rapeseed production averaged 39.3%. The K balance was negative, with an average net removal of 117.6 kg K ha-1 in the CK treatment annually, and 56.8 kg K ha-1 in the ＋K treatment. The results indicated that there was a significant negative relationship between yield increments by K application and soil available K content. Based on the relative yield of CK/＋K at 90% level, the critical level of soil available K （NH4OAc-extractable K） was 135 mg kg-1.