3In 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 to ha annually. The national production is about to 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.
4Potato in the worldTable 1. Potato production and yield in different part of the world(Source : FAO, 2008)Harvested area (ha)Production (t)Yield (t/ha)Afrique10,8Asie et Océanie15,7Europe17,4Amérique latine16,3Amérique du Nord41,2MONDE16,8
5Figure 1. Potato world production (1991 – 2007) (FAOSTAT)
6Potato in Morocco Table 2. Production area of potato in Morocco (Source: MAPM/ DDFP, 2010)Zone d'officeZone de DPASuperficie (ha)Production (T)GHARB4410155660SETTAT6725LOUKKOS365092040KHENIFRA483597 000MOULOUYA3375125670EL HAJEB4600DOUKKALA247574200CASABLANCA417073 030SOUSS-MASSA217060060RABAT-SALE313578 050HAOUZ213552825CHEFCHAOUEN202541 000OUARZAZATE70022100MEKNES195571 430TAFILALETE43011740EL JADIDA190049 600TADLA1203970KHEMISSET176530 615FES150045 000BEN SLIMANE122018 740TETOUAN101018 855AL HOCEIMA100017 175
7Labour charge is very important from planting till harvesting
9Phosphorus 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.
10In Morocco: Only 50 % of farmers use fertilizers
11Soil phosphus content in Saïs Region Source:Fertilty Map of MoroccoExecuted by the consortium:INRA – IAV - ENA
17A 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).
18Seven potato varieties (Desirée, Nicola, Barna, Pamela, Daifla, Labella, Marguerita) Combined with two phosphorus treatments:P0 : without any P application andP+ : 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.
19Nitrogen was added at the rate of 50kg N/ha at planting and another 50 kg N/ha at tuber formation as ammonium nitrateThe trial was implemented on May and harvested on August. The crop was under drip irrigation system ,Trial was well protected against parasites and weeds.
20At maturity for every treatments (V At maturity for every treatments (V*P) each ten plant have been harvested and tuber yield was estimatedThe 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.
21The responsiveness of variety “i” was calculated on the basis of: Vi: potato variety iTY: tuber yield of potato (t/ha) of variety iP+: treatment with added phosphorus as fertilizer.P0: treatment with no added phosphorus as fertilizer.
23Effect of phosphorus and genotype on tuber yield of potatoes
24Both 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+).
25Responsiveness of potatoes varieties to phosphorus fertilizer
26Figure 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%.
27Phosphorus use efficiency HypothesisPhosphorus use efficiencyCorresponds to grain yield per unit of P absorbed or phosphors utilization efficiency (PUZE) AndIs P absorbed per unit of available phosphorus or phosphorus uptake efficiency (PUPE).
29Genetic adaptation of plants to low phosphorus supply Mechanisms which improve P acquisitionMechanisms which improve P utilisationRoot morphological characteristicsRoot growth and distributionRoot diameterRoot-hair developmentMycorrhizal associationRoot physiological characteristicsP uptake systmP mobilization in the rhizospherePartitioning of P within the plantRemobilization of P within the plantP status of the harvested organEfficient utilization of P at the cellular levelIntracellular compartmentation of PMetabolic requirements for PFigure Mechanisms which improve genetic adaptation of plants to phosphorus-limited tropical soils. (Rao et al. (1999))
30ConclusionsWithin 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
31AcknowledgementsWorkers and technical staff at the experiment station of El Annaceur (Morroco) are gratefully acknowledged