Effects of the potassium application rate on lipid synthesis and eating quality of two rice cultivars

Lipid content has an important effect on rice eating quality,but the effects of fertilizer application rate on the lipid synthesis and eating quality of rice are not well understood.Potassium(K)has a strong influence on rice quality and the requirement for K fertilizer in rice is greater than for nitrogen(N)and phosphorus(P)fertilizers.To investigate the effects of K fertilizer on the lipid synthesis and eating quality of rice,we used Nanjing 9108(NJ9108,japonica)and IR72(indica)rice as experimental materials and four K levels:K0(0 kg ha^(-1)),K1(90 kg ha^(-1)),K2(135 kg ha^(-1))and K3(180 kg ha^(-1)).The results showed that the lipid content,free fatty acid(FFA)content,unsaturated fatty acid(UFA)content,malonyl-CoA(MCA)content,phosphatidic acid(PA)content,lipid synthesis-related enzyme activities and eating quality first increased and then decreased with increasing K in both cultivars.The maximum values were obtained under K2.However,the saturated fatty acid(SFA)content showed the opposite trend.No significant differences were found in pyruvate(PYR)content among the K treatments.The protein and oxaloacetic acid(OAA)contents and phosphoenolpyruvate carboxylase(PEPCase)activity of NJ9108 first decreased and then increased with increasing K,and the minimum values were obtained under K2;while IR72 showed the opposite trend and the maximum values were obtained under K1.Overall,increasing K optimized the fatty acid components and increased the lipid content and eating quality of rice by enhancing lipid synthesis-related enzyme activities and regulating substrate competition for lipid and protein synthesis.The optimal K application rate for lipid synthesis,eating quality and grain yield was 135 kg ha^(-1)for both cultivars.

Production Benefits of Double-Cropping Rice Under Optimized Application of Nitrogen and Potassium Fertilizers Combined with Chinese Milk Vetch and Straw Co-Returning to Fields

In order to explore the technology and effects of reducing nitrogen and potassium fertilizer applications in double-cropping rice,a field plot experiment was conducted to study the effects of optimized application of nitrogen and potassium fertilizers combined with returning Chinese milk vetch and straw to fields on yield,fertilizer utilization efficiency,net photosynthetic rate(Pn),stomatal conductance(Gs),intercellular CO_(2) concentration(Ci),chlorophyll content(SPAD value)and soil physical and chemical properties in late rice harvest period.The results showed that the optimized application of nitrogen and potassium fertilizers combined with the integrated technology of Chinese milk vetch and straw co-returning to the field could enhance the photosynthetic efficiency of double-cropping rice,increase rice yield,and enhance soil biological activity,especially T4 treatment involving the returning of Chinese milk vetch and straw to the field instead of 30%nitrogen fertilizer achieved the highest rice yield,fertilizer use efficiency,net photosynthetic rate and soil biological activity.Compared with the conventional fertilization treatment T2,the total rice yield of T4 treatment increased by 4.1%,among which the early rice and late rice increased by 6.3%and 2.4%,respectively;Pn,Gs and SPAD values of flag leaves at full heading stage significantly increased,and the contents of soil active organic carbon,alkali hydrolyzed nitrogen,available phosphorus and readily available potassium significantly increased.

Effects of Potassium Fertilizing Rates on Yield, Fiber Quality and Potassium Use Efficiency of Three Hybrid Cotton Cultivars

The effects of potassium （K） application rates on the yield, fiber quality and K fertilizer use efficiency of three hybrid cotton varieties （Jin102, Xiangzamian8, Siyang328） were studied in field experiment. Fertilizer rates of K2O 135 and 270 kg/hm2, representing 1x and 2x recommended K rates, were applied, no application of k fertilizer as the CK. The results show that the lint yield increased 39.13%-57.48%with potassium application, highly significantly. Al yield components of the three hy-brid cotton varieties increased with the increase of K application amounts. The bol number per plant, single bol weight and lint percentage were increased by 14.24%-40.29%, 3.59%-15.51% and 0.16%-4.89%, respectively, and the fiber length and specific strength also increased with the increasing K application amounts, showing no significant influence on Micronaire. When the K application amounts increased from 135 to 270 kg/hm2, the partial factor productivity （PFPk） reduced by 45.93%-48.01%, and the agronomic efficiency （AEk） reduced by 37.1%-42.9%. The PFPk and KE （K efficiency coefficients） of S328 were the highest among the three varieties, which also showed the strongest resistance to low potassium stress, and with no potassi-um fertilizer application （K0）, the lint yield of S328 was 5.54% and 11.19% higher than that of X8 and J102. The AEk of J102 was the highest, and its reward of K fertilizer was the greatest among the three varieties.

Effect of potassium on soil conservation and productivity of maize/cowpea based crop rotations in the north-west Indian Himalayas

Plots under conservation tillage may require higher amount of potassium(K) application for augmenting productivity due to its stratification in upper soil layers, thereby reducing K supplying capacity in a medium or long-term period. To test this hypothesis, a field experiment was performed in 2002-2003 and 2006-2007 to study the effect of K and several crop rotations on yield, water productivity, carbon sequestration, grain quality, soil K status and economic benefits derived in maize(Zea mays L)/cowpea(Vigna sinensis L.) based cropping system under minimum tillage(MT). All crops recorded higher grain yield with a higher dose of K(120 kg K2 O ha-1) than recommended K(40 kg K2 O ha-1). The five years' average yield data showed that higher K application(120 kg K2 O ha-1) produced 16.4%(P<0.05)more maize equivalent yield. Cowpea based rotation yielded 14.2%(P<0.05) higher production than maize based rotation. The maximum enhancement was found in cowpea-mustard rotation. Relationship between yield and sustainable indices revealed that only agronomic efficiency of fertilizer input was significantly correlated with yield. Similarly, higherdoses of K application not only increased the water use efficiency(WUE) of all crops, but also reduced runoff and soil loss by 16.5% and 15.8% under maize and 23.3% and 19.7% under cowpea cover, respectively. This study also revealed that on an average 16.5% of left over carbon input contributed to soil organic carbon(SOC). Here, cowpea based rotation with the higher K application increased carbon sequestration in soil. Potassium fertilization also significantly improved the nutritional value of harvested grain by increasing the protein content for maize(by 9.5%) and cowpea(by 10.6%). The oil content in mustard increased by 5.0% and 6.0% after maize and cowpea, respectively. Net return also increased with the application of the higher K than recommended K and the trend was similar to yield. Hence, the present study demonstrated the potential yield and profit gains along with resource conservation in the Indian Himalayas due to annual additions of higher amount of K than the recommended dose. The impact of high K application was maximum in the cowpea-mustard rotation.

Influence of Accompanying Anions on Potassium Retention and Leaching in Potato Growing Alluvial Soils

A column study was carried out to assess the influence of accompanying anions on potassium （K） leaching at potato growing sites with different soil textures （sandy loam and clay loam） in northwestern India. Potassium was applied in the top 15 cm layer of soil column at 30 and 60 mg K kg-1 through different sources having different accompanying anions （CI-, SO^-, NO3 and H2PO4-）. Maximum K was retained in the top 0-15 cm layer with a sharp decrease in K content occurring in 15 30 cm layer of the soil column. The trend was similar for both levels of applied K as well as frequency of leaching and soil type. The decrease of K content in soil column after four leaching events was maximum in case of Khanaura sandy loam, while only minor decrease was observed in Hundowal clay loam when K was applied at 60 mg K kg-1, indicating higher potential of clay rich soil to adsorb K. In general, the K leaching in presence of the accompanying anions followed the order of SO4^2-≤ H2PO42- 〈 NO3 = Cl-. Highest 1 mol·L^-1 CH3COONH4-extractable K was retained when K was applied along with SO4^2- and H2PO4 anions, and the least was retained when accompanying anion was Cl-. The influence of anions was more pronounced in the light textured soil and at high amounts of K application. Higher levels of K application resulted in higher losses of K, especially in sandy loam soil as observed from the leachate concentration. Among the different K sources, the maximum amount of K leaching was noticed in the soil column amended with KC1. After four leachings, the maximum amount of K leached out was 6.40 mg L-1 in Hundowal clay loam and 9.29 mg L-1 in Khanaura sandy loam at 60 mg K kg-1 of soil application through KC1. These concentrations were lower than the recommended guideline of the World Health Organisation （12.00 mg L-1）.

Screening of the Optimal Potassium Fertilization Rate for Maximizing Bulb Yield and Potassium Nutrient Evaluation in Fritillaria thunbergii Miq.

Background:The dry bulb of Fritillaria thunbergii Miq.is a traditional Chinese medicine,and is the leading product of the geo-authentic crude drugs‘Zhebawei’in Zhejiang Province.Fritillaria thunbergii requires more potassium(K)than nitrogen and phosphorus,while the response of F.thunbergii to K has rarely been studied.Objective and Methods:To evaluate the K nutritional status of F.thunbergii,a 2-year field experiment was conducted under six K application rates(0,40,80,120,160,and 200 kg K_(2)O ha−1)with two F.thunbergii cultivars(ZB1,narrow-leaf;ZB2,broad-leaf).Results:The bulbus Fritillariae Thunbergii(BFT)yield increased to a plateau with more than~120 kg K_(2)O ha-1.The BFT quality met the standard of Pharmacopoeia of P.R.China with more than 40.0 kg K_(2)O ha^(-1).Leaf K concentration was significantly correlated with BFT yield,and was more sensitive to K application rate as compared to those of stems and flowers.Potassium application extended the duration of rapid leaf-biomass accumulation and increased the accumulation rate.Two cultivars had similar response patterns to K application,but ZB2 had higher K partial productivity,leaf-biomass,and leaf K concentration than ZB1.Conclusion:108.4-128.0 kg K_(2)O ha^(-1) was the optimal K application range for BFT yield.The potassium nutrition index(KNI)model established based on leaf K concentration has biological significance and can be used for dynamic diagnosis of K nutritional status of F.thunbergii with both accuracy and simplicity.