Use Efficiency of Rice Nutrient in the M arginal Areas of Jianghan Plain

Li YANG，Hongyan GUO，Aiqing YOU，Guangquan ZHUANG，Jiaqiong WU，Yangmei NIE

1.Hubei Academy of Agricultural Sciences，Wuhan 430064，China；2.Dangyang Bureau of Agriculture，Dangyang 444100，China；3.Qianjiang Bureau of Agriculture，Qianjiang 433100，China

Fertilizer has become an important factor influencing the growth and development，yield and quality of rice［1-2］.The rational fertilization can promote the growth of rice，increase production，improve nutrient absorption，and improve fertilizer use efficiency［3-5］，which is an important technological path to develop agricultural production，improve crop yield and ensure the food security［6］.Fertilizer use rate is an important indicator for measuring the reasonability of fertilizer application，and a dynamic parameter that reflects the relationship among crop，soil，and fertilizer，subject to the effects of soil fertility，synergistic role ofnutrients，fertilization techniques and fertilization amount，crop varieties，soil moisture，climatic factors，cultivation managementmeasures and other factors.

Dangyang is a city in western Hubei province，People's Republic of China，lying 70 kilometers east of the Gezhouba Dam on the Yangtze River.In 1988 the State Council of the People's Republic of China elevated this from a county to a county-level city，and is currently under the administration of Yichang City.Dangyang used to be a strategic point in ancientwars.While agriculture remains a key industry in Dangyang，industrial production now includes output in the areas of foodstuffs，building materials，textiles，chemicals，electronics，machinery，energy and packaging.Dangyang，located in the transition zone between Jianghan Plain and western Hubeimountainous regions，is the marginal area of Jianghan Plain.The year-round rice area is about 30000 hm2in this city.For the understanding of the formulated fertilization and soil fertilizer nutrient use rate in this region，we carry out this experiment to further standardize the soil formulated fertilization technique，optimize fertilization structure，and improve the fertilizer nutrient use rate.

1 Materials and methods

1.1 Experimental materialsThe experiment was carried out in Yuyang Town，Dangyang City of Hubei Province.The plots for experiment are located in 111°52′33.3″E，30°43′12.8″N，with the field surface altitude of 60 m；the soil is the rice soil developed based on yellow-brown soil parent，and the basic nutrient status［7］of soil is as follows：organic matter（14.3 g／kg），pH（5.9），alkali-hydrolyzable nitrogen（113mg／kg），available phosphorus（8.3mg／kg），and available potassium（100mg／kg）.

The rice variety for experiment is Y Liangyou 1，and thewater sowing and transplanting are used.The sowing density is12000 per 667 m2，with the plant row spacing of 23 cm×24 cm.

1.2 Experimental design

1.2.1 Experimental processing.Eight treatments are set in this experiment，namely FP（conventional fertilization），FP-N（local farmer's fertilization without nitrogen），FP-P（local farmer's fertilization without phosphorus），FP-K（local farmer's fertilization with out potassium），OPT（formulated fertilization），OPT-N（formulated fertilization without nitrogen），OPT-P（formulated fertilization without phosphorus），and OPT-K（formulated fertilization without potassium）.

This experiment uses large plot design without repetition，to divide the plots into conventional fertilization plot and formulated fertilization plot.In the two plots，various treatments are set respectively，and the area of each treatment plot is 50 m2.The drainage and irrigation ditch is set in each plot，and the ridge set between the plots is covered with film.In addition to fertilization，other field management practices are also conducted at the same time in other plots.

1.2.2 The utilization amount of fertilizer and fertilization methods.The utilization amountof nitrogen，phosphorus and potassium nutrient treated with FP（conventional fertilization）and the fertilization methods，are determined according to the farmers'conventional fertilization in the experimental areas.The utilization amount of nitrogen，phosphorus and potassium is N 195.0 kg／hm2，P2O537.5kg／hm2，and K2O 60.0kg／hm2，respectively.

The fertilization amount under OPT（formulated fertilization）is recommended using abundance and deficiency index according to the test value.The utilization amount of nitrogen，phosphorus and potassium is N 120.0kg／hm2，P2O536kg／hm2，and K2O 60.0kg／hm2，respectively.In the process of application，60%of nitrogen fertilizer is used as the base fertilizer；20%of nitrogen fertilizer is used for tillering；20%of nitrogen fertilizer is used as earing fertilizer.Phosphorus fertilizer and potassium fertilizer are applied as the base fertilizer for one time.The nitrogen，phosphorus，and potassium fertilizers for the experimentare urea（containing N 46%，Sinopec Hubei Chemical Fertilizer Plant），superphosphate（containing P2O512%，Hubei Yang Feng Co.，Ltd.），and potassium chloride（containing K2O 60%，Germany Potassium Company）.

1.3 Data analysis and methods

1.3.1 Fertilizer nutrient use rate.Relative use rate of one fertilizer nutrient＝（to talabsorption of this nutrient under full fertilization treatment-total absorption of this nutrient under the treatment without this nutrient）／the utilization amount of this fertilizer nutrient under full fertilization treatment×100%.

1.3.2 The absorption of nutrient per 100 kg of crop economic yield.The absorption of one nutrient per 100 kg of crop economic yield（kg）＝Crop total absorption of this nutrient／Grain yield×100.

1.3.3 Agronomic efficiency of fertilizer.Agronomic efficiency of fertilizer＝Yield under full fertilization treatment-Yield under the treatment without this nutrient／The utilization amount of this fertilizer nutrient.

2 Results and discussions

2.1 The impact of formulated fertilization on fertilizer nutrient use rateThe rice yield results and fertilizer nutrient use rate under different treatments can be shown in Table 1.The data in Table 1 show that the nutrientuse rate of N，P2O5，and K2O in formulated fertilization is121%，38%，and 64%higher than that in conventional fertilization，respectively.

This experiment further indicates that the scientific and reasonable formula of nitrogen，phosphorus and potassium can significantly improve the nutrient use rate；the nutrient use rate when only the nitrogen fertilizer is applied in conventional fertilization is very low，and at the same time，it affects the absorption of phosphorus and potassium.This is consistent with Yang Li［5］，and Tong Jun［8］.

Table1 Thericeyieldresultsandfertilizernutrientuserateunderdifferenttreatments

2.2 The agronomic efficiency of nitrogen，phosphorus and potassium under different treatmentsThe agronomic efficiency under different treatments is shown in Table 2.The experimental results show that the agronomic efficiency of nitrogen under conventional fertilization is4.85 kg／kg，below the agronomic efficiency of nitrogen under formulated fertilization（7.91 kg／kg）；similarly，the agronomic efficiency of potassium in conventional fertilization（3.20 kg／kg）is less than the agronomic efficiency of potassium in formulated fertilization（4.50 kg／kg）.

However，the agronomic efficiency of phosphorus in conventional fertilization（15.68 kg／kg）is higher than the agronomic efficiency of phosphorus in formulated fertilization（7.29 kg／kg）.It is not high in comparison with the background value of available phosphorus in the experimental plots，which may be related to the low recommended amount of phosphorus in formulated fertilization.

The role of nitrogen nutrient in increasing the rice yield in formulated fertilization is significantly higher than the role of nitrogen nutrient in increasing the rice yield in conventional fertilization.The effect of nitrogen application in formulated fertilization is better than the effect of nitrogen application in conventional fertilization.

Whether it is formulated fertilization or conventional fertilization，the general trend is as follows：the absolute amount of yield increase of nitrogen fertilizer is the highest，followed by the phosphorus fertilizer，and potassium fertilizer play s a certain role in increasing yield.

It indicates that the soil nitrogen level and application rate of nitrogen are still themost critical factors affecting rice yield［9］.

Table2 Theagronomicefficiencyunderdifferenttreatments

2.3 The impact of formulated fertilization on nutrient absorptionNutrient absorption under different treatments is shown in Table 3.There is little difference in the nutrient absorption per 100 kg of economic yield between formulated fertilization and conventional fertilization，indicating that under different fertilization methods，the nutrient absorption per 100 kg of economic yield is relatively stable，and it can be regarded as a constant.

In terms of the nutrient absorption，there is the trend of potassium＞nitrogen＞phosphorus.The economic yield under formulated fertilization is8853 kg／hm2，and the amount of nitrogen fertilizer to be applied based on the yield is106.5 kg／hm2，basically in line with the formulated fertilization program；if the phosphorus and potassium are determined according to the yield，then the amount of phosphorus and potassium to be applied is13.5 kg／hm2，and 132 kg／hm2，respectively.

It further indicates that the practice of determining the nitrogen based on yield and determining the phosphorus and potassium according to the soil abundance under formulated fertilization，is in line with actual production.

Table3 Nutrientabsorptionunderdifferenttreatments

2.4 The economic and biological yield under different treatmentsCompared with conventional fertilization，the grain yield，stem and leaf yield and biological yield under formulated fertilization are increased by 313.5 kg／hm2，465.0 kg／hm2，and 778.5 kg／hm2，respectively，an increase of 3.67%，4.94%，and 4.33%，respectively，indicating that the formulated fertilization cannot only improve economic yield，but also improve the biological yield.

In the case of the same other inputs，the yield under formulated fertilization is313.5 kg／hm2more than that under conventional fertilization；the income under formulated fertilization is 877.5 yuan／hm2more than that under conventional fertilization；the input costs under formulated fertilization are 439.5 yuan／hm2less than that under conventional fertilization.

It can be clearly seen that the efficiency of formulated fertilization is significantly higher than thatof conventional fertilization.

Table4 Theeconomicandbiologicalyieldofriceunderdifferenttreatments

2.5 Nutrient content of grain and stem and leaf under different treatmentsCompared with the conventional fertilization，the nitrogen content of rice grain is increased significantly under formulated fertilization，an increase of 33.33%，but the nitrogen contentof stem and leaf declines significantly，a drop of27.59%.

The phosphorus content of grain is significantly decreased，a decline of15.90%，but the phosphorus contentof stem and leaf is increased，an increase of 8.62%.

The potassium content of grain and stem and leaf is little affected，because nitrogen is the main component of synthesized protein.The formulated fertilization may improve the quality of rice to a certain extent.

However，whether it is formulated fertilization or conventional fertilization，there is a common trend，namely the nitrogen content of grain is much higher than phosphorus and potassium content of grain；there are no significant differences between the content of phosphorus and potassium in the grain.

Table5 Nutrientcontentofgrainandstemandleafunderdifferent treatments

The potassium content of stem and leaf is significantly higher than the nitrogen content of stem and leaf，and the phosphorus content of stem and leaf is low.

The potassium content of stem and leaf is much higher than the potassium contentofgrain，but the phosphorus content of grain is higher than the phosphorus content of stem and leaf.

The nitrogen content of grain is higher than the nitrogen content of stem and leaf under formulated fertilization.There are no significant differences between the nitrogen content of grain and nitrogen content of stem and leaf under conventional fertilization.

3 Conclusions

（i）The reasonable application of nitrogen，phosphorus and potassium can significantly improve the fertilizer nutrient use rate.Compared with conventional fertilization，the formulated fertilization can improve the fertilizer nut rientuse rate，and N，P2O5，and K2O are increased by 121%，38%and 64%，respectively.The only application of nitrogen in conventional fertilization leads to low nutrient use rate，and affects the absorption and utilization of phosphorus and potassium.

（ii）There is no obvious difference in the nutrient absorption of rice between formulated fertilization and conventional fertilization，and there is also no obvious difference if without nitrogen，phosphorus and potassium treatment.It indicates that the amount of absorption of rice nutrient is relatively stable under different treatments，which can be regarded as a constant，but there are great differences the elements，namely potassium＞nitrogen＞phosphorus.The experiment also verifies that the practice of determining the nitrogen based on yield and determining the phosphorus and potassium according to the soil abundance under formulated fertilization，is in linewith actual production.

（iii）Compared with conventional fertilization，the economic yield，stem and leaf yield and biological yield are all significantly increased under formulated fertilization，indicating that the formulated fertilization can not only improve economic yield，but also improve the biological yield.In this experiment，the yield under formulated fertilization is313.5 kg／hm2more than that under conventional fertilization；the income under formulated fertilization is 877.5 yuan／hm2more than that under conventional fertilization；the input cost sunder formulated fertilization are439.5 yuan／hm2less than that under conventional fertilization.It can be clearly seen that the efficiency of formulated fertilization is significantly higher than that of conventional fertilization.

（iv）Compared with conventional fertilization，the formulated fertilization makes the rice grain nitrogen content increase dramatically，but makes the grain phosphorus content decline significantly；the impact on potassium content is little.Nitrogen is the main component of synthesized protein.The formulated fertilization may improve the quality of rice to a certain extent.

（v）Compared with the conventional fertilization，the nitrogen content of rice grain is increased significantly under formulated fertilization，an increase of 33.33%，and the application effect of nitrogen under formulated fertilization is better than that under conventional fertilization.Whether it is formulated fertilization or conventional fertilization，the general trend is as follows：the absolute amount of yield increase of nitrogen fertilizer is the highest，followed by the phosphorus fertilizer，and potassium fertilizer plays a certain role in increasing yield.

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