Potassium (K) and magnesium (Mg) levels and their balances are two factors affecting the growth of plant.  However, the responses of different crop cultivars to K/Mg ratios are less clear.  This study was aimed at assessing the different responses of tomato (Solanum Lycopersicum L.) cultivars to the different K/Mg supply ratios.  Three tomato cultivars (Zhongza 9 (ZZ), Gailiangmaofen (MF), and Jinpengchaoguan (JP)) were grown in pots with three different K⁺/Mg²⁺ ratios (4:0, 4:1 and 8:1, represented by K/Mg_4:0, K/Mg_4:1, and K/Mg_8:1, respectively).  Compared with K/Mg_4:1 treatment, the leaf chlorophyll content, net photosynthetic rate, and total biomass of tomato seedlings under K/Mg_4:0 treatments were decreased by 69.7, 89.1, and 53.1%, respectively.  The Mg deficiency symptoms were observed when the Mg content in shoot became lower than 4 mg g^–1 DW.  Compared with K/Mg_4:1 treatment, total biomass of tomato seedlings of K/Mg_8:1 treatment was decreased by 21.6%; the shoot and root Mg contents were decreased by 10.4 and 21.8%, respectively; and Mg uptake of tomato was reduced by 34.1%.  There were significant differences in biomass and Mg uptake for the three cultivars between the different K⁺/Mg²⁺ treatments.  The Mg uptake of the three different cultivars ranked as ZZ>JP>MF under Mg deficiency and high K condition.  In conclusion, the growth and Mg uptake and allocation of tomato were influenced significantly by imbalance K and Mg supply. JP and ZZ were the cultivars with the highest efficiency in Mg uptake. 

Excessive nitrogen (N) fertilization of high value horticultural crops is a common problem that not only increases the cost to farmers, but also negatively affects crop growth and the environment.  A three-year field experiment was conducted in an intensive kiwifruit orchard in Shaanxi Province, China to compare the effects of reduced N fertilization applied as urea (U), and controlled release urea (CRU) on the N nutrition of kiwi vines, fruit yield and quality, and nitrate-N accumulation in the soil profile.  The three treatments included a conventional N application rate (CF-U, 900 kg N ha^–1 yr^–1 as urea), two reduced N fertilization treatments where the amount of N fertilizer applied as U and CRU was reduced by 25% in 2013 and 2014, and by 45% in 2015.  The 25 and 45% reduced N treatments had no adverse effects on the N concentrations in leaves and pruning branches and the fruit yield and quality of kiwi vines.  However, they significantly enhanced the partial factor productivity of applied N (PFP_N) and the economic benefits, and reduced nitrate accumulation in the 0–200 cm soil profile.  The same benefits of reduced N fertilization were observed for both the U and CRU treatments, but the CRU treatment had the added benefit of decreasing the loss of nitrate through leaching.  We concluded that the current level of N fertilization in kiwi orchards is very excessive, and reducing the N fertilizer rate by 25–45% could not only guarantee fruit yield, but also reduce N accumulation and loss.