| Rice is one of the most important cereal crops, ranking first in yield and total production of food crops, which plays an important role in agricultural production in China as well as in the world. Since 1990s, rice production was confronted with a series of new problems, especially, (1) excessive fertilizer application reduced the nutrient use efficiency and deteriorate the entironment; (2) grain yield of rice does not increase with the increasing of fertilizers year by year. Therefore, the urgent work today is to harmonize the relation among high rice production, fertilizer utilization efficiency and environmental protection. In this research, some popular mid-rice varieties were used to study the effects of different nitrogen (N) fertilization methods on the grain production, grain quality and N use efficiency of rice to construct the best management system of rice nutrient with field trials conducted in Jianghan Plain and southeast of Hubei province at the same time. The main results are as below:1 Fertilizer applicationstatus of rice in Hubei ProvinceFertilization rate, grain yield and fertilizer use efficiency of rice at present of a total of 1027 farmers in rice-product areas of Hubei province was investigated in 2009 and 2010, respectively. The survey indicate that chemical fertilizerapplication rate in rice show an upward tendency; all of the fanners apply N fertilizers in rice paddies, however, only a few farmers apply organic fertilizer and micronutrient fertilizer. Average application rate of N, phosphorus (P), potassium (K) each year were 184.0 kg/hm2,63.8 kg/hm2 and 67.4 kg/hm2, respectively, and the ratio of N:P2O5:K2O was 1:0.35:0.37. These indicated that N application ratewas excessive, whereas, K application rate was not enough in rice paddies; moreover, P application rate was insufficient for late-rice but overdosed for mid-rice. The problem we face in rice fertilization are as follow:(1) a significant unbalanced ratio of organic fertilizer to inorganic fertilizer; (2) excessive N fertilization either as basal fertilizer or as basal and tillering fertilizer; (3) K fertilization was not enough and quite a number of farmers didn't apply K fertilizer; (4) significant unbalanced ratios in N:P2O5:K2O and in fertilization amount of base fertilizers to topdressing; (5) significant difference in fertilization rate and fertilization time among farmers in the same area; (6) low fertilizer use efficiency and rice yield. Therefore, it is necessary to establish the best nutrient management system for promote the grain yield of rice and nutrient use efficiency in Hubei province. 2 Effects of fertilization measures of nitrogen (N) on grain yield, grain quality and N-use efficiency of midseason rice in Hubei ProvinceFour popular midseason varieties of rice (Luoyou8, Guohaozayoul, Fengyou22 and Jufengyou72) were used to study effects of application technology of nitrogen (N) on grain yield, grain quality and N-use efficiency in Hubei province. The results showed that grain yield of modified farmer's fertilizer practice(FFP), super high yield (SHY) and modified SHY were more than that of FFP at Chibi with yield increase rate 10.0%,2.3% and 23.2%, respectively, in 2008; and 16.6%,11.8% and 22.6%, respectively in 2009. However, at Jingmen, grain yield of modified FFP, SHY and modified SHY were lower than that of FFP in 2008 and slightly more than that of FFP in 2009 with yield increase rate 2.0%,6.7% and 1.7%, respectively. At Chibi, nitrogen agronomic efficiency (AE) and nitrogen partial factor productivity (PFP) of modified FFP and modified SHY were higher than that of FFP; while, at Jingmen, PFP of N of modified FFP and modified SHY was significantly higher, whereas AE of them slightly higher than that of FFP. N-use efficiencies (NUE) of SHY at two field trial spots in two years were far lower than that of other treatments. Both modified FFP and modified SHY treatments achieved higher grain yield and higher NUE, which suggested that 20% reduction of nitrogen of FFP could increase grain yield as well as NUE. On the contrary, too much N application would not increase, even reduce grain yield. In addition, the optimized nitrogen management could also improve the grain quality of rice.3 Responses of grain yield of riceto soil Fertility and fertilization in Hubei provinceFengliangyouxiangl, a popular midseason varietie of rice was used to study responses of grain yield to soil fertility and fertilization by small field trials at Honghu in Hubei province. The grain yield of the control (no N application) reached 7855.0 kg/hm2 showed that soil N fertility was very high at Honghu. Grain yield of modified FFP, SHY and modified SHY were significantly more than that of FFP treatment. SHY did not achieve the highest grain yield, which indicate that excessive nitrogen application could not increase even reduce the grain yield. N application rate of FFP was lower than that of FFP and the local high-yield treatment, whereas N-use efficiency and grain yield of FFP were significantly higher than that the two latter treatments. These indicated that it is of feasibility to improve N-use efficiencies as well as to increase grain production by reducing N fertilization. Multi-spots experiment showed that the higher the soil fertility, the higher the rice grain-yield. The grain yield of FFP increased by 5.6% in average of all the spots, by 6.1% at high fertility fields and by 4.9% at low fertility field comparing with FFP, among them.As there was slight difference in N application rate between modified FFP and FFPat different experimental spots, so the increasing in grain yield and N-use efficiency were mainly due to the N fertilizer of the former distributed more to the late growth stage by top dressing times. Therefore, this optimizated N fertilization method based on the multi-spot experiments could be populization and application at Honghu... |
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