Soybean crop coefficients under different seeding rates and full and limited irrigation and rainfed management

The effects of soybean seeding rates on evapotranspiration (ETc) and grass- alfalfa-reference crop coefficients (Kco Kcr) were investigated under five (185,250, 247,000, 308,750, 370,500 432,250 seeds ha−1) (62, 82, 103, 124 144% the recommended rate 300,000 ha−1 in experimental region) different irrigation strategies (i.e. full treatment [FIT], limited 75% FIT 50% rainfed treatment). Kco Kcr values developed for each growth stage. seasonal ETc ranged from 460 mm to 489 2014 same 247,000 ha−1. In 2015, 308 conditions highest (432,250 395 308,750 Greater differences weekly observed across levels than rates, indicating that water availability has a greater impact rates. Kc strongly correlated with days after emergence (DAE) growing degree (GDD). maximum varied among was between GDDs 924 1200°C, corresponding R5 (beginning seed) R6 (full stages. Les effets des taux d'ensemencement de soja sur l'évapotranspiration et les référence cultures l'herbe la luzerne ont été étudiés pour cinq graines du recommandé dans région expérimentale) différentes stratégies d'irrigation (c'est-à-dire traitement complet limitée à pluvial). valeurs développées chaque stade croissance soja. L'ETc saisonnier varié le pluvial en avec même densité En l'ETc pluviales plus élevé On observé différences importantes hebdomadaire entre niveaux par rapports aux d'ensemencement, ce qui indique que disponibilité l'eau exerce un grand d'ensemencement. étaient fortement corrélées jours après levée degrés-jours (DJC). Le maximal selon DJC correspondant stades (graine initiale) complète). One major focuses modern production practices is attain improvements productivity (CWP) land, resources other inputs as necessitated by rising food fibre demands world population increasing negative impacts interference climate change agricultural productivity. regions irrigated agriculture, deficit are being adopted, which require accurate quantification use (evapotranspiration, ETc) obtain optimum yields better assessment management resources. Several methods have been used directly measure evapotranspiration, such lysimeters, Bowen ratio energy balance system (BREBS), eddy covariance system, remote sensing, flux profile techniques, scintillometry surface renewal. However, application aforementioned financial cost, difficulty maintenance lack scientific technical expertise operate maintain these complex systems interpret analyse data. Apart advanced can be determined good accuracy using conventional soil approach (Irmak al., 2008). Another estimate two-step method, relates (Kc) reference (ETref), typically alfalfa or grass (ETr ET0, respectively). challenges ET estimation procedure local coefficient data variety crops grown various practices. Moreover, most reported literature fully do not account settings, perhaps more importantly management, result either substantially considerably plant development, nutrient uptake yield, Kc. Two surfaces, (ET0) (ETr), commonly weather collection over ETref calculated. Determination important employing approach, vary conditions, crops, season crop. measured average curves given FAO-56 (Allen 1998) due timing magnitude stress (Payero & Irmak, 2013) also impacted residue cover (Odhiambo 2012). tabulated stages without measurements site-specific adjustments may lead inaccurate estimation. Therefore, it necessary derive experimentally an representative ETc. Djaman Irmak (2013) that, average, overestimated maize approximately 26% 2009 17% 2010, makes transferability locations (seeding conditions) challenging. Limited research (Kcr Kco, respectively) simultaneously environments aid For instance, Payero monthly grass-reference range 0.40–1.18 when averaged 2002, 2003 2005 seasons. al. daily ranging 0.20 1.12 0.27 1.47, respectively, significantly those FAO-56. expressed based base scales, (Stegman 1977), stage (Doorenbos Kassam, 1979; Sammis 1985), planting (Djaman 2013; Wright, 1982), percentage time harvest cutting cycles (Wright, then elapsed (Wright Jensen, 1978), cumulative ETo (Hill 1983), fraction thermal units (Amos 1989), leaf area development phenology 2013), index fractional green canopy 2013). Each scale some advantages drawbacks, depending availability. While numerous studies addressed density (rate) yield (Alessi Power, 1982; Bernacchi 2011; Carciochi 2019; Cui 2020; De Bruin Pedersen, 2008; Karam 2005; Nleya Timmons 1967; Umburanas 2018); single row versus twin performance; (Bruns, 2011); environmental interactions (Chen Wiatrak, 2010; Corassa height, economic return variables partial (Cox Cherney, whole partitioned components (Mourtzinis 2021); weed (Arce 2009); spacing 2014); risk associated (Gaspar 2020); partitioning genetic gains (Suhre 2014), (rainfed, irrigation) extremely rare, identified very topics effective significant knowledge, information gaps. To bridge this knowledge gap locally available practices, current conducted following specific objectives: (i) quantify assess impact(s) Kcr, (ii) develop functions relating DAE GDD (iii) tabulate settings. Some primary materials details presented Sandhu (2022), but pertaining specifically design determination ETr will here. field 2015 seasons Research Laboratory engineering facilities at University Nebraska-Lincoln (UNL), South Central Agricultural (SCAL) near Clay Center, Nebraska, USA. site located latitude 40°34′40.88″ N longitude 98°07′54″ W elevation 552 m above mean sea level. dominant series Hastings silt loam soil, capacity (θfc) 0.34 m3 m−3, permanent wilting point (θwp) 0.14 saturation (θsat) 0.51 m−3 slope 0–1% (Irmak, 2010), root depth during mid-season 1.20 2013, 2014). considerable variation precipitation within well long-term climatic variables, including annual precipitation, minimum temperature, 680 mm, 25°C −5°C, respectively 2010). A 4.45 ha set up had randomized complete block design, consisting 20 treatments replicated 3 times. two factorials first factor ha−1), second strategy four FIT, non-irrigated [rainfed] control plot (experimental unit) 122 long 6.1 wide eight rows) 0.76 spacing. randomly assigned every unit replication (block). Thus, subjected all treatments, resulting total block. 2014, cultivar Pioneer 92Y83 relative maturity 2.8 planted 28 May. Plants emerged 6 June harvested 2 October, length 127 days. 9 June, plants 15 October 115 both years, 0.03–0.04 north–south direction. Agronomic information, planting, emergence, harvesting, amount date fertilizer applications seasons, Table 1. Flexstar + Roundup AMS Irrigation applied subsurface drip (SDI) installed senior author (S. Irmak) maintained year before, sustain high performance. Driplines direction 0.40 below middle row. east–west laterals 1.52 m. emitters pressure compensating 1 L h−1 discharge (Netafim-USA, Fresno, Calif., USA). emitter 0.45 flow individual model M&WMR precision flowmeters USA) 0.378 deliver precise plots irrigation. 100% automated, connected Galileo Controller (Galcon, Galcon Kfar Blum, 1215000) control, monitor record fertigation applications, telemetry monitoring troubleshooting. ridge-till several years before initiating research. Weekly status depths 0.30, 0.60, 0.90, 1.50 neutron probe moisture meter (model 4302, Troxler Electronics Laboratories, Inc., NC, throughout access tubes replications (in 40 out 60 plots). healthy plants. readings determine amounts timings analyses. 2. managed practised maintaining 45 90% prevent accommodate storage potential precipitation. During did commence until pod (R3), characterized presence 4–5 pods one uppermost main stem nodes leaf. At stage, sensitive stress. deep soils, if content stored much Specht 1989). events occurred 41, 31 respectively. scheduled, providing 102, 76 51 drier warmer atmospheric leading higher evaporative compared season. Precipitation obtained automated station site. run-off calculated United States Department Agriculture-Natural Resources Conservation Service (USDA-NRCS) curve number method (USDA-NRCS, 1985). Based site's hydrologic group, land use, condition, numbers estimated 60, 78 89 dry, normal wet Due event 44 August season, while negligible 0.5 treatments. small 2.2 mm) Deep percolation computer program written Microsoft Visual Basic (Bryant 1992; 2009). Inputs include air incoming short-wave radiation, humidity, wind speed, rainfall, dates amounts, initial date, parameters (permanent point, capacity, particle size distribution bulk density) rooting depth. summary Tavg, RH, Rs, VPD u2 3. Substantial variations events, 0.30 34 55 mm. comparatively wetter 2015. (from harvest) 447 211 wettest months above-normal 167 173 accounted 37.2 38.7% rainfall received 74 DAP marked end 2014. May normal. Approximately 40.3% early June. 85 July less later water-intensive resulted extensive low period (4 August) mid-September (12 September), R3.5 R6.5 (56 95 DAP). 23 5.8% averages irrigations 29 8 August, coinciding R3 R4 (62 72 general, demand temperatures higher, solar humidity lower Tmax 3.9% similar Tmin 2.5% 5.7% Tavg 3.5% 2.2% respect average. RH 6.8% 5.2% 2015; 4% 10% Rs 3.2% 6.7% respective averages. portion (June–September), 5.5% 11.1% u2, RHavg 9.7, 8.9, 1.9 51% (June–September) 22°C 1.2°C (20.8°C). lowest 76.9% slightly (75.5%). (reproductive soybean) agreed trend. value (0.99 kPa), decreased months. September (1.07 kPa) (0.98 VPD, terms yield. Additionally, earlier physiological shorter evident Daily ET0 plotted function Figures 1(a) (b). 0.90 11.8 day−1 5.7 day−1, whereas 1.60 11.5 almost 5.6 day−1. 0.80 8.2 4.5 1.30 7.5 4.4 Maximum 14 (17 2014) (98 2015). variability vegetative stages, 30 DAP, variable periods reproductive they associate Kcr. magnitudes Figure 2(c). 1403°C 1378°C 20°C (21 July; 54 DAP) 17.7°C (6 September; soybean, late temperatures, explains (115 day daylength varieties daylength. (or twice week) trends 4. reduced evaporation transpiration caused dry surface. declined transpiration. reached their maxima 1170–1180°C R5.5 (seed enlargement) (pod beginning turn mature colour) 53, 58, 61 63 rainfed, 62 (when treatments) recorded ha−1, 1200 1250°C 660 730°C GDD, corresponded R2 bloom) frequent 770°C ETc, patterns. observed, 35, 42, 46 48 When 39 existed suggest (Table 4). Higher longer although 472 348 trend Seasonal widely (2005) 261–541 262–498 388–506 2004. (2014) 452–600 2007 473–579 2008. regimes 5-11. levels. They interannual level initiated 37 16 therefore, measurement obtained. 0.15 normally (2013). 0.49 1.39, 0.36 1.15, 0.19–1.34 0.14–1.07 occurrence consequently evaporation. increased progression period, senescence. As affected applied, notable pronounced functions, incorporated into modelling processes utilize equations calculations practical practitioners, producers, consultants, managers professionals. third-order polynomial fit (Tables 5–8). usually irrigation, rainfed). 0.33 0.88 vs 0.32 0.93 relationship. Similarly, ranges 0.30–0.85 0.30–0.86, GDD. stronger response Similar results (2013), who experienced maize. best developing Stegman (1977) fourth-order relationships DAE. mentioned position development. third- polynomials maize, Kang (2003) fifth-order sorghum. years. indicate dependent affecting demands, and/or affect uptake. research, exhibited treatment, 0.50–1.33, 0.49–1.39, 0.49–1.39 0.49–1.33, 0.37–1.05, 0.36–1.15, 0.36–1.12 0.39–1.08 9). 1.17, 1.30, 1.16, 1.16 1.33 conditions; 1.29, 1.25, 1.18 FIT; 1.18, 1.36, 1.39 1.26 1.24, 1.33, 1.28, 1.29 1.27 185,250, 1200°C (late September) no particular difference values. 0.21 1.32, 0.22 1.26, 0.19 1.34 10). Generally, 93 already initiated. 1.14, 1.10, 1.04 1.10 1.23, 1.20, 1.25 (average 2005), August. (Glycine max [L.] Merr.) Since effect GDDs. (if first) settings should contribute toward making robust within-season decisions, assessments projections work paper part investigating fundamentals coupled dynamics, (IRL) Professor UNL. Partial funding project provided NE Soybean Board grant agreement 65068. Field Data analyses, interpretation, writing, revisions, etc. done Penn State University. Rupinder former MS Ph.D. student post–doc supervision Irmak. Trade names commercial products solely reader constitute recommendation endorsement authors institutions. thanks his IRL team members, L. Odhiambo, assisted upon reasonable request.