Effects Of Irrigation Frequency And Phosphorus Application Rate On Biomass And Grain Yield Of Winter Wheat

In order to clarify the effects of irrigation frequency and phosphorus application rate on population biomass and grain yield formation of winter wheat under water-saving conditions, two experiments were carried out during 2007-2008 (rich rainfall year, 218.8 mm during winter wheat growing period) in Baoding and 2008-2009 (moderate rainfall year, 102.2 mm during winter wheat growing period) in Gaocheng County with locally commecial winter wheat cultivar Henong 822 and Ji 5265 respectively. The experiments during the two winter wheat growing seasons were arranged as split plot arrangement, with irrigation frequency as main plots ( including 0, 1, 2 and 3 frequency during the growing period on the basis of suitable pre-sowing soil moisture, expressed as W0, W1, W2 and W3, respectively ), and phosphorus application rate as split plots (including P2O5 0, 75 and 150 kg/ha, expressed as P0, P1 and P2 respectively). The main results were summarized as follows:1. During the two years, irrigation frequency had significant effects on population culm number. The culm numbers of W1, W2 and W3 with irrigation were significantly higher than those without irrigation in W0. But the difference of culm numbers among W1, W2 and W3 was not significant during 2007-2008. The culm number of W1 was significantly lower than W2 and W3, but insignificant between W2 and W3 after booting during 2008-2009. The culm numbers among the three levels of phosphorus application rates were insignificant.2. The difference of dry matter accumulation among the four irrigation levels was generally insignificant during 2007-2008. Only the dry matter accumulation of W3 with irrigation was highest, and significantly higher than that without irrigation in W0 in maturity, and the difference of dry matter accumulation among W1, W2 and W3 was not significant. During 2008-2009, the dry matter accumulation of W2, W3 after booting stage was significantly higher than W0 and W1, but it was insignificant between W2 and W3. Dry matter accumulation of W2 was the highest in the four irrigation levels at maturity. During the two years, the effects of phosphorus application rates on dry matter accumulation was statistically insignificant after booting.3. The precipitation during the two growing years waa different. As a result, the difference of LAI among different irrigation levels during 2008-2009 with moderate rainfall was higher than that during 2007-2008 with rich rainfall. The difference of LAI among the four irrigation levels was not significant at most growing stages during 2007-2008, but it was significant at middle and late growing stages during 2008-2009, with the order W0W2>W3>W0 during 2007-2008, but W3≈W2>W1>W0 during 2008-2009. The grain yields of P1 and P2 were all significantly higher than that of P0 during the two years. But the grain yield of P1 was the highest during 2007-2008 with more rainfall, but that of P2 was the highest during 2008-2009 with less rainfall. During the two years, the grain yield of P2 was the highest under W1 and W2 conditions, that of P1 was the highest under W3. Under W2 conditions, however, the grain yield of P1 was the highest during 2007-2008 with more rainfall, but that of P2 was the highest during 2008-2009 with less rainfall. These results showed the compensation effects between phosphorus and water supply, i.e., high grain yield can be achieved by different pathaway either"less water and more phosphorus"or"more water and less phosphorus". 6. Both irrigation and P application increased the accumulation of N, P and K by wheat plant, but the increaments were affected by rainfall. The effects of irrigation frequency on nutrient accumulation was less significant in rich rainfall year than in moderate rainfall year, when the accumulation amount of N and P increased with the increase of irrigation frequency. The effects of P application rate on the accumulation amounts of N, P and K were also different owing to different rainfall years: its effects on N and K accumulation amounts during 2007-2008 was less significant than during 2008-2009, but the effects on P accumulation amount during 2007-2008 was more significant than during 2008-2009. Nutrient production efficiencies were also affacted by different rainfall years. The nutrient production efficiencies of wheat with appropriate irrigation and P fertilization were the highest.7. The water consumption was statistically significant among different irrigation levels during different years. The water productive efficiencies were all W0>W1>W2>W3 during the two years, although the water productive efficiency was statistically significant among all irrigation levels during 2007-2008, but significant only between W0 and W3 during 2008-2009. According these results, the water productive efficiency can be improved through decreasing irrigation under rich or moderate rainfall year. The water consumption was not significant among different phosphorus levels during the two years. The water productive efficiency increased with the increase of phosphorus application rate, but the water productive efficiency among different phosphorus levels was not significant during 2007-2008, but significant during 2008-2009, meaning that the water productive efficiency can be increased through increasing phosphorus application under moderate rainfall year.According to the results,it is recommended that two irrigations during the growing period be needed, with P2O5 150 kg/ha applied for satisfactory grain yield of winter wheat under moderate rainfall (about 100 mm during winter wheat growing period) in Hebei Plain of China. In rich rainfall year, however, one irrigation be sufficient, with P2O5 75 ~150 kg/ha.