Responsiveness of different potato (Solanum tuberosum) varieties to phosphorus fertilizer Daoui K., R. Mrabet, A. Benbouaza, and E.H. Achbani Institut National de la Recherche Agronomique (Maroc)

Introduction

In the Mediterranean Basin, potato is occupying an overall area of about one million ha and producing 18 million tons of tubers, In Morocco, potato occupies an area of about 50000 to 58000 ha annually. The national production is about 1000000 to1400000 tones so with a national main yield of about 23 t/ha which is below potential yield of about 40%. Optimizing phosphorus fertilization is one way to reduce the gap between actual and potential yield.

Potato in the world Table 1. Potato production and yield in different part of the world (Source : FAO, 2008)   Harvested area (ha) Production (t) Yield (t/ha) Afrique 1 541 498 16 706 573 10,8 Asie et Océanie 8 732 961 137 343 664 15,7 Europe 7 473 628 130 223 960 17,4 Amérique latine 963 766 15 682 943 16,3 Amérique du Nord 615 878 25 345 305 41,2 MONDE 19 327 731 325 302 445 16,8

Figure 1. Potato world production (1991 – 2007) (FAOSTAT)

Potato in Morocco Table 2. Production area of potato in Morocco (Source: MAPM/ DDFP, 2010) Zone d'office Zone de DPA Superficie (ha) Production (T) GHARB 4410 155660 SETTAT 6725 206 500 LOUKKOS 3650 92040 KHENIFRA 4835 97 000 MOULOUYA 3375 125670 EL HAJEB 4600 144 250 DOUKKALA 2475 74200 CASABLANCA 4170 73 030 SOUSS-MASSA 2170 60060 RABAT-SALE 3135 78 050 HAOUZ 2135 52825 CHEFCHAOUEN 2025 41 000 OUARZAZATE 700 22100 MEKNES 1955 71 430 TAFILALETE 430 11740 EL JADIDA 1900 49 600 TADLA 120 3970 KHEMISSET 1765 30 615 FES 1500 45 000 BEN SLIMANE 1220 18 740 TETOUAN 1010 18 855 AL HOCEIMA 1000 17 175

Labour charge is very important from planting till harvesting

Phosphorus in question

Phosphorus is one of major mineral nutrients required by Potato crop and its management in soil is critical. In fact, Potato requires a high amount of phosphorus for optimum growth and yield, However, P uptake and use is also dependant on genetic variability with the crops as well as the P fate in the environments including the soil. Accordingly, a better understanding of mineral application and use by crops is one way for enhancing crop yields with a minimum impact on environment and reducing production costs. The use of genetically enhanced plants with improved P acquisition efficiency may represent a sustainable solution to increase crop yields.

In Morocco: Only 50 % of farmers use fertilizers

Soil phosphus content in Saïs Region Source: Fertilty Map of Morocco Executed by the consortium: INRA – IAV - ENA

Fez

MEKNES

ELHAJEB

Objectifs The objective of this study is to assess, under field conditions, responsiveness of different potato varieties to mineral phosphorus application.

Materials & methods

A field trial was conducted at El Annaceur ((INRA, Morocco) situated 20 km far from Fès at latitude 33°41’, longitude 4°,50’ ; height 1345 m. Soil characteristics are: clay (27%), silt (53%) and sand (20%). pH water (8,4). NO3-  (11,6 mg/kg). Organic Matter (2,80 %), P2O5 (Olsen) (67 mg/kg) and K2Oexangeable (520 mg/kg).

Seven potato varieties (Desirée, Nicola, Barna, Pamela, Daifla, Labella, Marguerita) Combined with two phosphorus treatments: P0 : without any P application and P+ : 90 kg P2O5/ha as super triple phosphate (45%)). The experimental design was a split plot with three replications, P on main plots and varieties on subplots. Every subplot consisted on one line of 3m long of each variety separated on both sides by the check one (variety: Desirée) at distance of 0.70m. Ten tubers by variety were planted on each line.

Nitrogen was added at the rate of 50kg N/ha at planting and another 50 kg N/ha at tuber formation as ammonium nitrate The trial was implemented on May and harvested on August. The crop was under drip irrigation system , Trial was well protected against parasites and weeds.

At maturity for every treatments (V At maturity for every treatments (V*P) each ten plant have been harvested and tuber yield was estimated The data were subjected to analysis of variance procedures (SPSS). Standard errors of the means were calculated. NKS test was applied to compare measured parameters from variety.  

The responsiveness of variety “i” was calculated on the basis of: Vi: potato variety i TY: tuber yield of potato (t/ha) of variety i P+: treatment with added phosphorus as fertilizer. P0: treatment with no added phosphorus as fertilizer.

Results

Effect of phosphorus and genotype on tuber yield of potatoes

Both variety (V) and phosphorus (P) have a significant effect on tuber yield of potato while interaction (V*P) had no significant effect on this parameter (figure 1). Tuber yield varied between 16 t/ha for treatment (Barna (P0)) and 36 t/ha for treatment Pamella (P+). Phosphorus improves tuber yield by about 25%. .The variety Pamela gave the highest main tuber yield (34 t/ha) and performed well in both situations of P nutrition (P0 and P+). 

Responsiveness of potatoes varieties to phosphorus fertilizer

Figure 2. Responsiveness of different potatoes varieties to phosphorus fertilizer Responsiveness of varieties to phosphorus application varied between 9% and 71% (figure 2). The variety Desirée showed the highest responsiveness to P application with 71% of improvement of tuber yield, while the varieties Daifla, Labella and Pamela responses to P application was on average only 10%. The varieties Nicola, Margarita and Barna responded to phosphorus application by respectively 18, 27 and 49%.

Phosphorus use efficiency Hypothesis Phosphorus use efficiency Corresponds to grain yield per unit of P absorbed or phosphors utilization efficiency (PUZE) And Is P absorbed per unit of available phosphorus or phosphorus uptake efficiency (PUPE).

Genetic adaptation of plants to low phosphorus supply Mechanisms which improve P acquisition Mechanisms which improve P utilisation Root morphological characteristics Root growth and distribution Root diameter Root-hair development Mycorrhizal association Root physiological characteristics P uptake systm P mobilization in the rhizosphere Partitioning of P within the plant Remobilization of P within the plant P status of the harvested organ Efficient utilization of P at the cellular level Intracellular compartmentation of P Metabolic requirements for P Figure Mechanisms which improve genetic adaptation of plants to phosphorus-limited tropical soils. (Rao et al. (1999))

Conclusions Within this experiment, even if just for one year, we do find genetic variability to phosphorus responsiveness among different potatoes varieties. This indicates that choosing efficient variety may guarantee an improvement of tuber yield with less phosphorus fertilizer demand. This work should be reconducted. More measures should be made to characterize genotypes and elucidate differences in performances among those genotypes

Acknowledgements Workers and technical staff at the experiment station of El Annaceur (Morroco) are gratefully acknowledged