Potato Response to Polyhalite as a Potassium Source Fertilizer in Brazil: Yield and Quality

Abstract

<jats:p>Polyhalite (PH) is a hydrated sulfate evaporite mineral containing potassium, calcium, magnesium, and sulfur, nutrients all required in significant quantities by crops, but has limited evaluation as a fertilizer for potato (<jats:italic>Solanum tuberosum</jats:italic> L.). Fertilizer source and application rate field trials were conducted to evaluate PH as a fertilizer for potato production in the weathered tropical soils in Brazil. We selected two locations in the potato producing region of Southeast Brazil in 2015–16, one trial was conducted during the wet season at Tapira in São Paulo and the other during the winter season at Casa Branca in Minas Gerais. A common blend, 4–14–8, was made with either muriate of potash (MOP), sulfate of potash (SOP), or PH as the K source; with kieserite and gypsum added to the SOP to make a synthetic PH with similar composition; P either as single super phosphate (SSP) for the MOP blend or mono ammonium phosphate (MAP) for the PH and SOP blends; and N as urea adjusted for the N in MAP. All blends were applied at four application rates of 62, 125, 187, and 249 kg K/ha. A control was also included consisting of N and P as urea and MAP but no K, Ca, Mg, or S. Total and marketable yields as well as potato quality including dry matter, starch, soluble solids, hardness, and crunchiness were measured at harvest using standard techniques. At Tapira, potato yields increased linearly with increasing K application rate from 22.4 t·ha<jats:sup>−1</jats:sup> for the control to the highest yield of 29.2 t·ha<jats:sup>−1</jats:sup> and were higher for PH and SOP than MOP (28.8, 29.2, and 25.3 t·ha<jats:sup>−1</jats:sup>, respectively). At Casa Branca, yields increased from 31.5 t·ha<jats:sup>−1</jats:sup> for the control to 42.4 kg·ha<jats:sup>−1</jats:sup> at the 62 kg K/ha application rate with no further increases at higher rates and no differences among fertilizer blends at any application rate. Polyhalite blend increased dry matter and starch at the higher application rates compared with MOP and SOP at Tapira and increased potato hardness and crunchiness at the optimum 62 kg K/ha application rate at Casa Branca. Yield response was similar for PH and SOP but quality differences between these two fertilizer blends were observed even though they were similar in composition. Differences between PH and MOP may be related either to Cl or lack of Mg in the MOP blend. PH performed well as a fertilizer for potatoes as it produced equal or higher yields and provided benefits to potato quality when compared with MOP or SOP as a K source in a common fertilizer blend.</jats:p>

Potassium Fertilization for Fresh Market Potato Production in Tropical Soils

“…3). The absence of an effect of different K fertilizer application timings (preplanting and prehilling) on the specific gravity of tubers has also been reported in the literature (Kumar et al, 2007, Mohr andTomasiewicz, 2012;Noor et al, 2012;Mello et al, 2018). On the other hand, the specific gravity of potato tubers commonly decreases with the application of KCl, either in the planting furrows (Mohr and Tomasiewicz, 2012;Silva and Fontes, 2016) or before hilling (Mohr and Tomasiewicz, 2012;Silva and Fontes 2016), even under adequate water conditions.…”

“…3b-3d). Conversely, Mello et al (2018) found the maximum potato yield with a rate of 300 kg K 2 O ha -1 in a sandy soil with medium concentration of exchangeable K, while the maximum tuber yield was reached with a rate of 75 kg K 2 O ha -1 in a loamy sand soil with low exchangeable K. In the site-year with low exchangeable K in the soil, the increase in the total tuber yield in response to K fertilization may be related to the increase in the tuber mean weight (Fig. 3b, 3e), which increased 97% (62 g) with the rate of 276 kg K 2 O ha -1 ; in comparison, the increase was only 21% (14 g) at 83 kg K 2 O ha -1 in the site-year with a high soil test K. It was also observed that potato shoots had died at 80 DAE in the control plots of the experiment in the low soil test K because of an intense K remobilization to the tubers, which are stronger sinks (Kolbe and Stephan-Beckmann, 1997).…”

“…The nutritional functions of K are related to photosynthesis, enzymatic activity, the synthesis of proteins, carbohydrates and fats, and photoassimilate translocation (Coskun et al, 2017;Westermann, 2005;Zelelew et al, 2016;Tränkner et al, 2018). These functions induce shoot growth (Koch et al, 2019), result in a higher number of tubers per plant (Zelelew et al, 2016) and a larger tuber yield (Mohr andTomasiewicz, 2012, Li et al, 2015), increase the total soluble solids (Abd El-Latif et al, 2011;Noor et al, 2012) and protein (Abd El-Latif et al, 2011) contents, and determine the firmness of potato tubers (Mello et al, 2018). On the other hand, K fertilization may also decrease the dry matter (DM) content (Pauletti and Menarin, 2004;Silva and Fontes, 2016), the levels of starch (Li et al, 2015) and protein (Quadros et al, 2009), and the specific gravity of tubers (Mohr and Tomasiewicz, 2012;Silva and Fontes, 2016).…”

“…In soils with high exchangeable K concentrations, tuber yield responses to the application of K fertilizers may be negative (Pauletti and Menarin, 2004;Nava et al, 2007;Li et al, 2015). Under low or medium soil K availability, fertilization increases the number of tubers per plant (Silva and Fontes, 2016) and the tuber yield (Nava et al, 2007;Silva and Fontes, 2016;Mello et al, 2018). However, the poor correlations usually observed between potato crop responses in tuber yields and K fertilization (Mohr and Tomasiewicz, 2012;Shi et al, 2019), or between tuber yields and the initial levels of exchangeable K in soil, suggest that several factors, such as water availability and K interactions with other nutrients, may also affect potato crop productivity (Li et al, 2015).…”

“…On the other hand, the specific gravity of potato tubers commonly decreases with the application of KCl, either in the planting furrows (Mohr and Tomasiewicz, 2012;Silva and Fontes, 2016) or before hilling (Mohr and Tomasiewicz, 2012;Silva and Fontes 2016), even under adequate water conditions. According to Mello et al (2018), the influence of K on tuber DM content is complex and dynamic. The absence of an effect of K fertilization on the specific gravity of the tubers in the present study could be explained by the adequate water supply (rainfall and irrigation) in the three site-years (Fig.…”