effect of different levels of additional potassium on yield and industrial qualities of potato (Solanum tuberosum L.) in an irrigated arid region, The

American Journal of Potato Research,  May/Jun 2003  by AbdelGadir, A H,  Errebhi, M A,  Al-Sarhan, H M,  Ibrahim, M

• E-mail
• Print
• Link

Accepted for publication 31 March 2003.

ABSTRACT

Soils and irrigation waters in Saudi Arabia are naturally rich in potassium (K). In spite of this, farmers and large-scale agricultural companies usually add K fertilizers to various crops without soil and water testing and whether or not the crop requires high amount of K. The objective of these experiments was to study the response of fresh tuber yield, specific gravity, and frying quality of processed potato to different levels of additional K under farmer conditions. TWo field experiments were conducted during the 2000-2001 and 2001-2002 growing seasons in Wadi Addawasir (latitude 20-21 N, longitude 45-46 E), Kingdom of Saudi Arabia. The experimental layout was a randomized complete block design with five K levels (0-100 kg K^sub 2^O ha^sup -1^) and four replicates. Water and soils in this region contained more than 10 and 200 ppm K, respectively. Results indicated that there were no statistical differences (P

ADDITIONAL KEY WORDS: Chip color, specific gravity, potassium sulfate, irrigation water.

INTRODUCTION

In the kingdom of Saudi Arabia, potato (Solarium tuberosum L.) is mainly produced in arid lands under center-pivot irrigation systems. Average yields vary between 20 and 40 t ha^sup -1^. The crop is judiciously fertilized with N, P, and K and other elements based mainly on practical experience as there is a lack of recommendations based on correlation/calibration research. There is a general belief among farming communities in this region of the world that a higher and a better quality yield of potato crop is always obtained when K is added in large quantities. Although the potato crop requires heavy input of K for high yields (Errebhi et al. 1998), appropriate credits should be given to soil and water K. It is well documented that K does affect potato quality and yield. Insufficient K results in reduced potato yield and smaller-sized tubers (McDole 1978; Satyanarayana and Arora 1985). Other workers found significant tuber yield response to K fertilization (Westermann et al. 1994a; Panique et al. 1997). However, excess K fertilizer was reported to reduce specific gravity (Schippers 1968; McDole 1978; Westermann et al. 1994a, 1994b).

On the other hand, Davenport and Bentley (2001) found that potato yield and quality did not respond to K fertilizer although soil tests for K were low. Similarly, Panique et al. (1997) observed a lack of yield response to K in six of eleven sites. In addition, the results of studies on the effect of K on potato frying quality were erratic and reached no definite practical recommendations (Eastwood and Watts 1956; Kunkle and Holstad 1972).

In an attempt to fine tune fanner fertilizer practices to meet plant K requirements, field trials were conducted to determine if additional potassium enhanced potato yield and quality.

MATERIALS AND METHODS

This research was conducted during the growing seasons of 2000-2001 and 2001-2002 in commercial farmers' fields irrigated with center pivots in Wadi Addawasir region (latitude 20-21 N, longitude 45-46 E), Kingdom of Saudi Arabia. Each season, a different field was used due to crop rotation.

Soil samples were collected from each experimental site prior to planting at 0-20 cm depth and their properties were given in Table 1. In each season, an experimental area was chosen in the middle of the field and divided into 20 plots separated by 2 m as border. Plot size was 10.0 x 9.0 m (10 rows) and 8.0 x 12.6 m (14 rows) in the 2000-2001 and 2001-2002 seasons, respectively. Plots were arranged in a randomized complete block design with four replications. All plots received basic application of 247 kg N, 253 kg P^sub 2^O^sub 5^, and 215 kg K^sub 2^O ha^sup -1^. However, fanners usually apply an additional amount of 100 kg K^sub 2^O ha^sup -1^ as pre-plant. Five treatments (0, 25, 50, 75, and 100 kg K^sub 2^O ha^sup -1^) were therefore studied. The sources of granular fertilizers were 11-29-19 and K^sub 2^SO^sub 4^ (0-0-50). The sources of soluble fertilizers were urea (46-0-0) and KNO^sub 3^ (13-0-46). For the liquid fertilizer the source was 2-52-8. Granular fertilizers of the basic application or the treatments were hand spread before planting. Soluble or liquid fertilizers of the basic application were fertigated seven times through the center-pivot irrigation system. The potato cultivar, Hermiz, was used in both seasons and planted in rows (90 cm apart) at 25- to 28-cm spacing between plants. Planting dates were 25 October 2000 and 19 October 2001.

Plant leaf samples were collected at 45 and 60 days after emergence by collecting the fourth fully expanded leaves and analyzed for total N, P and K content. At least 33 to 42 leaves were collected from each plot. Total N in leaves was determined by wet digestion using Kjeldahl method, whereas P and K were determined by dry ashing using spectrophotometer and ICP (Ryan et al. 2001). Water samples were also collected several times during the growing season and analyzed for EC, pH, K, Ca, Mg and Cl (Greenberg et al. 1992). The K concentration in the irrigation water used in this study varied from 12.9 to 17.7 ppm (Table 2). Total quantities of irrigation water applied in 2001-2001 and 2001-2002 were 7,738 and 7,898 m^sup 3^ ha^sup -1^, respectively. These quantities supply additional 120 and 168 kg K^sub 2^O ha^sup -1^ to soils in 2000-2001 and 2001-2002 season, respectively