Phosphorus and Potassium Uptake, Partitioning, and Removal across a Wide Range of Soybean Seed Yield Levels

Abstract

Maintenance of adequate soil phosphorus (P) and potassium (K) levels is critical for profitable soybean [Glycine max (L.) Merr.] production. To accomplish this, precise knowledge of soybean P and K uptake, utilization, and removal is critical, yet a comprehensive study characterizing these requirements across wide‐ranging seed yield environments is nonexistent for modern soybean production systems. Using six site‐years and eight soybean varieties, plants were sampled at six growth stages, partitioned into their respective plant parts, and analyzed. Distinctly different uptake patterns and rates were found between P and K, where soybean accumulated greater relative amounts of K by R1 and 91 to 100% of its season‐long K total by R5.5, compared with only 68 to 77% of its season‐long P total. Removal of P (0.0054 kg P kg−1 grain) and K (0.016 kg K kg−1 grain) with the seed was consistent across environments and varieties and displayed strong relations with yield (R2 = 0.89–0.92). For each kilogram increase in yield, total P and K uptake increased by 0.0054 kg and 0.017 to 0.030 kg, respectively. The difference between total uptake and removal for each nutrient resulted in average nutrient harvest indices of 81 and 49% for P and K, respectively. However, significant variation in total uptake and nutrient harvest indices existed due to the environment, not variety, and was more pronounced for K, resulting in significant variability in the amount of K removed in stover. These results can be incorporated into future fertility recommendations to improve P and K management for profitable and environmentally sound soybean production.

Soybean seeding rate and fertilizer effects on growth, partitioning, and yield

“…Gaspar et al. (2017a, 2017b, 2018) found higher grain yields (i.e., 5500 kg ha −1 ) decreased the time interval for nutrient accumulation and termed this the “lag‐phase”. Increased DM through increased seeding rates (i.e., ≥ 222,400 seeds ha −1 ) and subsurface MESZ applications likely reduced the “lag‐phase” of soybean nutrient uptake.…”

“…Similar DM and HI among seeding rates and adequate soil nutrient concentrations indicated no differences in grain nutrient accumulation should be expected. Macronutrient removal in grain was previously reported to remain unaffected by soybean grain yield potential or variety when soil nutrient concentrations were sufficient (Gaspar et al., 2017a,b). Grain nutrient concentrations within seeding rate and fertilizer treatment ranged from 59 to 60 g N kg −1 , 5.09 to 5.34 g P kg −1 , 19.8 to 20.1 g K kg −1 , 3.03 to 3.29 g S kg −1 , and 39.8 to 40.8 mg Zn kg −1 (data not shown) and were in agreement with current removal values (Warncke et al., 2009; Bender et al., 2015).…”

“…Grain yield responses to MOP were not observed presumably due to sufficient soil test K concentrations at all locations. Significant reliance of grain K on vegetative remobilization as compared to continued soil uptake during grain‐fill emphasizes the importance of maintaining pre‐plant and mid‐season soil K levels for soybean production (Mallarino, Webb, & Blackmer, 1991; Clover & Mallarino, 2013; Gaspar et al., 2017b). Although grain yield is influenced by environmental conditions (i.e., precipitation and temperature), maintaining sufficient soil nutrient concentrations allows growers to capitalize on grain yield potential when favorable growing conditions occur.…”

“…However, grower interest in N, P, K, S, and Zn applications continues to increase due to volatile spring environmental conditions, variable soil texture, decreased atmospheric S deposition in the north‐central United States, perceived increases in micronutrient deficiencies, and to ensure yield potential of modern higher‐yielding cultivars (i.e., yield potential >4500 kg ha −1 ) (Chien et al., 2016; Havlin et al., 2014; Hitsuda, Toriyama, Subbarao, & Ito, 2008; Osborne & Riedell, 2006; Sutradhar, Kaiser, & Behnken, 2017; Tamagno, Sadras, Haegele, Armstrong, & Ciampitti, 2018). Gaspar, Laboski, Naeve, and Conley (2017b) reported grain K requirements relied on vegetative remobilization past R5.5 emphasizing the importance of K tissue concentrations to support soybean DM and K accumulation prior to grain‐fill. Additionally, subsurface fertilizer applications at planting may increase both early and late season nutrient availability and help mitigate inconsistent grain yield responses to foliar fertilizer applications as grain N, P, S, and Zn requirements rely upon soil uptake after R5.5 rather than vegetative remobilization (Gaspar et al., 2017a, 2017b, 2018; Orlowski et al., 2016).…”

Phosphorus Management in High‐Yield Systems

“…Gill et al (2004) found similar differences across wheat cultivars, although there was variability in the ratio of yield to P uptake. Gaspar et al (2017) showed that soybean took up 23 to 32% of its total P uptake during the reproductive stages of growth (R1–R5.5), with a very strong relationship between P uptake and yield across several varieties and site years. Advanced P management in high‐yield systems demands an understanding of the P uptake patterns by the cultivars and hybrids being grown.…”