No abstract

Nitrogen (N) and potassium (K) are essential macronutrients for plants growth; however, the mechanism by which K mediates negative effects on ammonium-sensitive plants is still poorly understood. We hypothesized that K supplies may enhance antagonistic ammonium stress while improving nitrate nutrition function, which wheat seedlings were grown in sand culture in the presence of two N forms (ammonium; nitrate) supplied at two rates (2, 10 mmol L−1) and three K levels (0.5, 5, 15 mmol L−1). We found that a high N rate increased plant biomass under nitrate nutrition, while it had a negative effect under ammonium nutrition. Compared with nitrate, biomass was depressed by 54% or 85% for low or high N rate under ammonium. This resulted in a reduction in gas exchange parameters and a subsequent decrease in growth variables and nutrient uptake, whereas these parameters increased significantly with increasing K levels. Moreover, in principal components analysis, these variations were highly clustered under nitrate nutrition and highly separated under ammonium nutrition. Our study shows a clear positive interaction between K and N, suggesting that high K supply relieves ammonium stress while improving growth vigor under nitrate nutrition by enhancing nutrient uptake and assimilate production in wheat plants.

To face the great challenges of ensuring food security and environmental sustainability, agricultural production must be improved by high yield and high resource utilization efficiency (HYHE). We recently addressed this challenge and evaluated yield potential by surveying 735 farmers in 2008–2012 and then conducting 6 rice field experiments in 2008–2013 with large demonstration areas in 2010–2013 aimed to actualize the HYHE in Jiangsu Province, China. The survey result showed that the averaged N rate, grain yield and N partial factor productivity (PFPN) of the farmers were 336.7 kg ha−1, 8131.8 kg ha−1 and 24.2 kg kg−1, respectively. Through controlling total N rates and adjusting the application timing, the yield and the PFPN of optimal N managements (OPT) were increased by 5.9% and 37.6% with 31.4% reduction in N supply amounts for 6 experimental sites, and the yield increased by 5.6% for large demonstration areas compared with farmers’ fertilizer practices (FFP), respectively. In conclusion, although the soil properties of the different regions varied, HYHE could be achieved by regulating the N management practices, thus contributing to higher rice production and lower environmental costs from intensive agriculture in Jiangsu, China.

In terms of tillering potential, the aboveground portions of rice are significantly influenced by the nitrogen level (NL) and transplant density (TD). To obtain a suitable combination of NL and TD, five NLs (0, 90, 180, 270 and 360 kg ha-1) and two TDs [high density (HD), 32.5×104 hills ha-1; low density (LD), 25.5×104 hills ha-1] were used in the rice experiments during 2012 to 2014, in Jiangsu, China. The results showed the highest grain yield of rice obtained at HD and LD when N supply was 180 and 270 kg ha-1, respectively. That’s because there are more tillers per unit area, a larger leaf biomass fraction of total aboveground biomass, a larger leaf area index (LAI) and a larger canopy photosynthesis potential (CPP) at HD. It can be concluded that, higher rice planting densities resulted in less N inputs, while more N is needed to improve single plant actual tiller ability under low density to offset the reduced planting density. When the NL was more than 180 kg ha-1, the actual tillering ability of a single plant at LD was 20% more than that at HD. Based on these results, the supply of 1 kg N can be replaced by adding approximately 1000 planting hills per hectare. Therefore, adjusting the transplant density could be an efficient method to reduce the amount of nitrogen fertilizer and increase the nitrogen fertilizer use efficiency, which is very conducive to the sustainable development of agriculture.

SUMMARYRice (Oryza sativa L.) is one of the most important cereal crops in the world and a potentially important source of zinc (Zn) in the diet. The improvement of Zn content of rice is a global challenge with implications for both rice production and human health. The objective of the present study was to identify the effects of nitrogen (N) fertilizer rates and Zn application methods on Zn content of rice by evaluating rice production on native soils with different Zn availabilities in 2010/11. The results indicated that Zn application increased rice grain yield and Zn content in grains compared with the control; however, this effect was also affected by the native soil Zn availability, N fertilizer rate and Zn fertilizer application method. The native soil Zn status was the dominant factor influencing grain yield and grain Zn content in response to Zn fertilizer application. Grain Zn content ranged from 19·74 to 26·93 mg/kg under the different Zn statuses. The results also indicated that Zn application method has a significant influence on grain yield. Application of Zn fertilizer to the soil was more effective than the foliar spray on rice grain yield; however, the foliar spray resulted in a greater increase in grain Zn content when compared with soil application. Grain Zn content was affected by application method and displayed the following general trend: soil application + foliar spray > foliar spray > soil application. The experiments investigating the effect of N fertilizer rate combined with Zn application method showed a clear increase in both grain yield and Zn content as the N fertilizer level increased from 200 to 300 kg/ha. In addition, the results also indicated that N content and accumulation increased in all plant tissues, which suggests that Zn application might influence the uptake and translocation of N in rice plants. These results suggest that soil application in addition to a foliar spray of Zn should be considered as an important strategy to increase grain yield and grain Zn content of rice grown in soils with low background levels of Zn-associated diethylene triamine pentaacetate acid. Moreover, this process could be further strengthened by a high N application rate. In conclusion, these results demonstrate the potential of optimizing nutrient management using Zn fertilizer to obtain higher grain yields and higher grain Zn content in fields with low native Zn status.

No abstract

No abstract

No abstract