Potassium‐fertilizer management in winter oilseed‐rape production in China

Abstract

Optimal potassium (K) fertilization is beneficial for oilseed-rape (Brassica napus L.) yield and quality. However, the discrepancy between the high K demand of winter oilseed rape and low soil fertility and insufficient potassium input has limited the sustainable development of oilseedrape production. A series of on-farm experiments in the key winter oilseed-rape domains of China was conducted from 2004 to 2010 to evaluate K-fertilizer management for winter oilseed rape. Currently, the average NH 4 OAc-extractable K content in the 0-20 cm soil layer is 89.1 mg kg -1 indicative of "slight deficiency". In addition, farmers in China usually fail to use sufficient K fertilizer in oilseed-rape production, the average mineral-potassium-fertilizer input in 2010 being only 35 kg K ha -1 , far lower than the recommended rate of potassium for winter oilseed rape. Adequate potassium fertilization significantly raises seed yield. The average yieldincrease rate for the major production regions due to K-fertilizer application was 18.5%, and the average K fertilizer-use efficiency 36.1%. Based on the negative correlation between yield response to potassium fertilization and available soil K content, a soil-K-test index was established for winter oilseed rape with a threshold value for NH 4 OAc-extractable soil K of 135 mg kg -1 . When available soil K-content is below this threshold value, more K fertilizer should be applied to achieve high seed yield and to increase soil fertility. The major challenge for K-fertilizer management in winter oilseed-rape production in China will be to guide farmers in the different regions in making reasonable use of K fertilizer through soil K-testing technology in order to maintain both seed yield and soil fertility.

On-farm trials of optimal fertilizer recommendations for the maintenance of high seed yields in winter oilseed rape (Brassica napus L.) production

“…But the relationship between soil NH 4 OAc-K content and relative yield was weak in our study because of minor response to K fertilization. The average yield increase rate associating with K fertilization was 11.5%, similar to that reported by Ren et al (2013). The relationship between plantavailable soil K supply, seed yield of the 0-K treatment and relative yield was also poor.…”

“…In 2013, more than 36.4 million hectares of lands were devoted to growing oilseed rape with a production of 59,172.5 million tons (FAOSTAT 2014). The use of mineral fertilizer plays an important role in achieving high seed yields (Sieling and Kage 2010;Ren et al 2013). Many experiments on the fertilization of field and potted oilseed rape have been showed that the optimal N application rates range from 90 to 200 kg N ha −1 (Fismes et al 2000;Cheema et al 2001;Ozer 2003;Rathke et al 2005;Malhi et al 2007).…”

Effects of Ascophyllum nodosum seaweed extracts on lettuce growth, physiology and fresh‐cut salad storage under potassium deficiency

“…The negative impact of K deficiency on photosynthesis, transpiration and stomatal conductance is well documented . Potassium deficiency symptoms may not necessarily be readily visible or observed in the field owing to a rapid reallocation of K within the plant, so the fundamental importance of K may not be directly appreciated . The content of chlorophylls (Chl b and total Chl) was not affected by either of the K levels used in this study (375 or 125 mg L −1 ) or by SW application (Table ).…”

Effects of citrate on the dissolution and transformation of biotite, analyzed by chemical and atomic force microscopy

“…The location of potassium loss in biotite determines the release pattern of potassium in two ways including (1) exchange interaction, H + or Na + cation exchanges K + from the edge of the (h k 0) and interlayer via kinks or defect sites on the biotite (0 0 1) surface, which will not lead to evident alteration on a biotite structure (Hu et al, 2011); (2) hydrolysis, H + reacts with Al-O-Al and Si-O-Si to break the lattice charge-balancing and release K + , which will destroy the mica crystal structure (Ganor et al, 2009;Munson, 1985). Biotite has abundant K, which is one of the three most essential nutrients for plants (Ren et al, 2013;Samal et al, 2010;Steingrobe and Claassen, 2000). Where K deficiency is common, such as in China, India, Sri Lanka and regions of Southeast Asia (Li et al, 2009;Pathak et al, 2009), biotite breakdown is very important for improving available K in soils (Manning, 2010 Previous studies suggest that mica dissolution rates vary as a function of pH much as they did in other aluminosilicates.…”