The 20-year study, published in the journal Field Crops Research, investigated methods to improve K deficiencies prevalent in large areas of soil across China.
“In China, the current priority for agricultural policy is high crop yields to meet the food demands of a large and growing population. Long-term sustainable high crop yields require integrated management practices, including the application of K fertilizers,” the researchers wrote.
While modern cultivars were more effective at absorbing potassium and had higher yield potential, in China maize yields had not substantially increased due to adverse weather conditions, they claimed.
K fertilizer had worked to increase grain yields where applied in north China, but around 40% of south China’s agricultural land remained potassium deficient, they explained.
“An understanding of K use and efficiency in the soil–crop system is, therefore, essential for the development of more sustainable K fertilization, especially as many Chinese soils are deficient in K.”
Integrated, sustainable method…
The researchers found that integrated management practices worked best to improve the K value of Chinese soil.
Potassium-rich maize cultivars could be reintegrated into the soil after harvesting, they said, to improve K absorption and thus reduce the application rate of K fertilizers.
In addition, deep-rooting crops could be used to ensure K below 40 cm is utilized, they explained.
Potassium’s vital function
Potassium is an essential plant macronutrient. It plays a key role in the synthesis of cells, enzymes, protein, starch, cellulose, and vitamins; in nutrient transport and uptake, in augmenting resistance to abiotic and biotic stresses and enhancing crop quality.
Despite its vital function, research into K optimization has been neglected – in favor of nitrogen (N) and phosphorus (P) – because its affects on cereal production is less discernible than N and P.
“Improvement in K use efficiency can effectively alleviate K deficit status and decrease the potential negative impacts of nitrogen fertilizers in China,” the researchers wrote.
Optimal rates
The purpose of this research was to clarify the effects and efficiency of chemical K fertilizers on crop yields and examine changes in soil K content (to a depth of 100cm) and input-output balance after long-term chemical application.
Earlier studies concluded that K application under farming management practices increased summer maize grain yields by 9.9–14.9% compared with crops with no K application. This study endorsed previous conclusions, the researchers said.
Researchers noted significant increases to maize yields after K application and rates of 113 and 225 kg per hectare year on year increased average yields by 15.1 and 13.8%.
The optimal application rate was calculated at 150kg per hectare each year.
However they pointed out that results were dependent on certain variables, such as genotypic crop variations in efficiency of K uptake and differences in plant density.
They added: “If the K application rate was exceeded or not synchronized to crop K demand, not only did grain yield cease to increase, but the K use efficiency also decreased and leaching of exchangeable K occurred.”
Source: Field Crops Research
http://dx.doi.org/10.1016/j.fcr.2014.04.016
‘Long-term effects of potassium fertilization on yield, efficiency, and soilfertility status in a rain-fed maize system in northeast China’
Authors:Shaojun Qiu, Jiagui Xie, Shicheng Zhao, Xinpeng Xu, Yunpeng Hou, Xiufang Wang, Wei Zhou, Ping He, Adrian M. Johnston, Peter Christie,Jiyun Jin