Methodology Of Fertilizer Recommendation Based On Yield Response And Agronomic Efficiency For Wheat

The inappropriate application of fertilizer has become a common phenomenon in wheat plantingsystem in China and has led to nutrient imbalances, inefficient use and large losses to the environment.Having access to a science-based fertilizer recommendation is critical for improvement of fertilizer useefficiency in high yielding crops. However, how to establish fertilizer recommendation suitable forsmall-holder farmers remains a challenge. This paper described a new fertilizer recommendationmethod named Nutrient Expert for Wheat decision support system based on yield response andagronomic efficiency using datasets from2000to2011. This system applies Site-specific NutrientManagement (SSNM) principles, which includes the use of the Quantitative Evaluation of the Fertilityof Tropical Soils (QUEFTS) model to determine crop nutrient uptake for a specific yield. Fertilizerrecommendation based on yield response and agronomic efficiency is an alternative approach developedfor use, which meets the adaptability of different sizes of field plots and considers the soil indigenousnutrient supply and N, P and K interactions. This methodology has the advantages of good timeliness,simple and economical, and easy to master and widely to apply, especially when soil testing and plantdiagnosis technology are not available. It is believed that Nutrient Expert for wheat decision supportsystem will become the popular method of fertilizer recommendation in China. The results of this studyshowed as follows.(1) The statistic of data from all experiments showed that the grain yield was averaged at5950kg/ha,the rates of N, P2O5, and K2O fertilizer application were172kg N/ha,102kg P2O5/ha, and91kgK2O/ha, respectively. At the yield ranges of <4,4~6,6~8,8~10, and10~12t/ha, the N requirementfor per ton of grain yield for winter wheat were22.9,24.4,24.8,25.0, and27.6kg, and P were6.5,6.4,6.5,6.8, and7.6kg, and K were15.2,17.5,19.0,22.6, and36.3kg, respectively. However, forspring wheat at the yield ranges of <4,4~6, and6~8t/ha, N for per ton of grain yield required were24.3,25.4, and27.0kg, P were3.3,3.4, and4.1kg, and K were49.8,32.3, and17.3kg,respectively.(2) In the QUEFTS model, two boundary lines described the minimum and maximum internalefficiencies (IEs, kg grain per kg nutrient in above-ground plant dry matter) of N, P and K. Theminimum and maximum IEs for wheat were28.8and62.6kg grain per kg N,98.9and487.4kggrain per kg P, and23.0and112.9kg grain per kg K. The QUEFTS model predicted alinear-parabolic-plateau curve for balanced nutrient uptake with target yield increasing. The linearpart continued until the yield was approximately at60%~70%of the potential yield, and22.8kg N,4.4kg P and19.0kg K were required to produce1000kg grain. The corresponding N:P:K ratio was5.18:1:4.32, and the corresponding IEs were43.9,227.0and52.7kg grain per kg N, P and K,respectively. The QUEFTS model simulated balanced N, P and K removal by1000kg grain were18.3,3.6and3.5kg, respectively, with a N:P:K ratio of5.08:1:0.97. Approximately80%,82%and18%of N, P and K in total above-ground plant material were presented in the grain and removedfrom the field. (3) The soil indigenous nutrient supply is an important parameter to characterize the soil nutrient status,the yield responses to N, P and K are most important indices for evaluation of fertilizer effect indifferent soil fertility, and the agronomic efficiency is a most important parameter to evaluate theyield increase by fertilizer application. The result showed that the average soil indigenous nutrientsupplies in China were122.6kg N/ha,38.0kg P/ha, and120.2kg K/ha, respectively. The meanyield responses of wheat to N, P and K were1.67,1.00and0.80t/ha. The mean agronomicefficiency values of N, P, and K were9.4,10.2, and6.5kg/kg, respectively. The mean relative yieldof N, P and K were0.76,0.85and0.90. The relative yield could be used to classify the soilindigenous nutrient supply. The values of relative yield for N were0.60,0.77and0.88for low,medium, and high indigenous N supply, respectively. The values of relative yield for P were0.79,0.87and0.93for low, medium, and high indigenous P supply, respectively, and values of relativeyield for K were0.84,0.90and0.94for low, medium, and high indigenous K supply, respectively.(4) There was a significant negative relationship between yield response and soil available nutrient, andsignificant negative exponential relationship between yield response and indigenous nutrient supply,and a significant negative linear correlation between yield response and relative yield. It was alsodemonstrated a quadratic equation between yield response (x) and agronomic efficiency (y)(P<0.05). The relationship between yield response and agronomic efficiency for N wasyN=-0.3729x_N~2+6.1333xN+0.1438(R~2=0.76, n=601), for P was y_P=-0.5013x_P~2+8.3209x_P+2.3907(R~2=0.65, n=288), and for K was y_K=-1.6581x_K~2+9.099x_K~2+0.7668(R=0.58, n=379). Theseequations were all incorporated as part of the Nutrient Expert for Wheat fertilizer recommendationdecision support system.(5) Field validation based on Nutrient Expert for Wheat confirmed that the QUEFTS model could beused as a practical tool for this decision support system to make fertilizer recommendation. Alsomultiple field experiments helped to validate the feasibility and showed that fertilizerrecommendation based on yield response and agronomic efficiency could reduce the N fertilizerapplication by7.6%~55.8%, and adjust the P and K fertilizer, the gain yield increased by0.1%~4.3%, and net profit was improved by522~1734yuan/ha. The agronomic efficiency andrecovery efficiency of N, P and K mainly showed a trend to increase or were improved significantly.It concluded that Nutrient Expert for Wheat could be used as an alternative method to makefertilizer recommendations in China.