16 Better Crops/Vol. 101 (2017, No. 1) Abbreviations and notes: N = nitrogen; P = phosphorus; K = potassium; S = sulfur; B = boron; Fe = iron; Zn = zinc. IPNI Project GBL 62. UNITED STATES T he “Yield gap” can be defined as the dif- ference between the yield that is attainable in a region (maximum yield without abiotic or biotic stresses) and the actual on-farm yield. Selecting the best crop and nutrient management practices (e.g., genotype selection, row spacing, planting date, and nutrient 4Rs—right source, rate, time, and place), and considering their interactions with each other and with the envi- ronment (soil, weather), will directly impact the size of this gap. In recent years, several soybean studies have evaluated the effect of fertilizer applications or crop management practices in- dividually, but research investigating the impact of these factors on seed yield in an integrated system approach is scarce. “Liebig’s Law of the Minimum” establishes that growth is controlled by the most limited resource or factor. Following this rationale, when nutrients are supplied in a complete and balanced program according to plant demand, crop yield will then be limited by some other factor such as light interception or water avail- ability. The objective of this work was to test an integrated farming system approach that simul- taneously considers both crop nutrition and crop management practices, and thereby further the understanding of cropping systems based on the concept of Ecological Intensification (Cassman, 1999). Soybean studies were carried out in 2014 and 2015 at Scandia, Kansas, under both dryland and irrigated conditions each year. For each of the four site-years, five farming systems ranging from very low to intensive use of inputs were tested. The following treatments were evaluated: Common Practices (CP), Comprehensive Fertilization (CF), Production Intensity (PI), Ecological Intensification (EI), and Advanced Plus (AP) (Table 1). The main difference between CP and CF treatments was that fertilizer (P, K, and S) was added for the CF treatment. For the PI treatment, seeding rate was increased by 23,000 seeds/A over CP, row spacing was narrowed from 30 to 15 in., and no fertilizer was added. The EI treatment is a combina- tion of CF and PI, with a seeding rate of 134,000 seeds/A, row spacing of 15 in., balanced macro plus micronutrient fertilization, and fungicide/insecticide applications. Average precipitation for both seasons was 16.3 in. and the irrigated scenario received an average of 6.9 in. of water. Lastly, AP was similar to the EI treatment, but with a more intensive (2x) use of micronutrients and fungicide/insecticide. Detailed crop phenology (V4, V6, R1, R5, R7), seasonal plant dry biomass, nutrient concentration, and canopy coverage were evaluated in all site-years. Harvest index (HI) and N Harvest Index (NHI) were de- termined as follows: By Guillermo Balboa, Mike Stewart, Fernando Salvagiotti, Fernando García, Eros Francisco, and Ignacio Ciampitti Intensive Soybean Management: An Integrated Systems Approach Ecological intensification impacted soybean yield, biomass and N uptake. Narrow row spacing, high seeding rate, other best production practices, and balanced nutrition increased partitioning efficiency for biomass, measured by seed harvest index (HI), grain N, and N HI (NHI). Partial factor productivity of fertilizer (PFPf) increased when best production and fertilizer management practices were implemented in combination, with 19% and 28% increases under irrigated and dryland scenarios, respectively. An integrated approach, simultaneously considering multiple management factors in a farming system, is needed for closing exploitable yield gaps. Table 1. Treatment description for soybean experiment at Scandia, Kansas, aver- age of 2014-2015 growing seasons. Treatments CP CF PI EI AP Seeding rate, seeds/A 111,000 111,000 134,000 134,000 134,000 Row spacing, in. 30 30 15 15 15 Fertilization No (P-K-S) No (N*-P-K-S) (N*P-K-S) Micronutrients No No No 1x (Fe, Zn, B)* 2x (Fe, Zn, B)** Fungicide/Insecticide No No No 1x** 2x** CP=common practices, CF= comprehensive fertilization, PI= production intensity, EI= eco- logical intensification (CF+PI), AP= advanced plus. *Applied at R3. **Applied at R1 and R3. Fertilizer rates in lb N-P 2 O 5 -K 2 O-S/A: (56-9-31 -8) and (56-13-43-11) for dryland and ir- rigated. Treatment CF did not receive any N application. 0 10 20 40 60 80 Feet RVI High: 56 Low: 3 RVI Index, Irrigated Soybean Scandia Kansas. July 2016 Sampled area for biomass Ratio-Vegetation Index (RVI) map for irrigated scenario. Greener means healthy vegetation Block 1 Block 2 Block 3 Block 4 Block 5 AP EI PI CF CP CP EI CF PI AP PI AP EI CP CF AP CP CF EI PI CF CP PI EI AP Aerial image showing differences in the Ratio-Vegetation Index [the ratio of infrared reflectance over visible red reflectance (NIR/VR)] for irrigated soybean at Scandia, Kansas. Green color is correlated with healthy growth.