Proposal: Fertigation of potatoes

in arid and semi arid Moroccan regions

* Coordinator: Professor Ahmed Skiredj.

* Experimental sites: Bouznika and Tadla regions in Morocco .

* Duration of the project: 3 years.

* Introduction:

In arid and semi arid agricultural areas, crop productivities are severely limited by a combination of drought, heat and salinity (Bruns and Caesar, 1990). Usually salt resuts in an important plant growth reduction and yield decrease of many crops (Greenway and Munns, 1980; Chauhan R.P.S., Singhs S.P. and Ram S., 1990). This would be the case of potato yield limitation in Bouznika and Tadla regions, which are suffering of salt problems (Skiredj, El Ganga and Bekraoui, 1994; Skiredj and El Attir, 1998). Various factors can be responsible of this decrease in plant growth and yield under saline conditions: physiological drought and osmotic effect (Casas et all, 1991), weak root development in relation to that of shoots (Bruns S. and Caesar K, 1990) and nitrogen nutrition perturbation in relation to root uptake, foliar tissue nitrate assimilation (Soltani, 1988 ; Gouia, 1991) and interactions with other nutrients carried out by fertigation, potassium in particular (Yadav B.R. and Paliwal K.V., 1990). In our previous prospecting and surveys (Skiredj, El Ganga and Bekraoui, 1994 ; Skiredj and Cherif, 1995) variability of yields seemed to be related to that of N/K ratios of applied fertilizers, plant material used in moroccan salty regions and to cultural practices as a strategy to overcome salt limitations. In fact, enhancing the productivity of land with drought, heat and salinity problems is by all means a big task and quite expensive. Generally, growers choose economical ways for this control, such as use of tolerant varieties, adapted cultural operations, deep soil ploughing, organic matter and chemical amendments. Since salt correction in an area can be achieved by all these economical means which should be seen as a major strategy to overcome salt limitations, studies on enhancement of plant production under salt conditions should be done, not only with independent field trials but also by proceeding with an integrated approach, combining all effective means of salt reduction, in a natural context of grower farms.

* General objectives: The overall objective is to improve potato yield and quality in integrated systems of production, combining different known effective practices which limit salt effects, such as deep soil plowing, good edging, manure amendments, fertilizer management, micro nutrient foliar spray and fertigation.

* Specific objectives:

* Prospecting in Bouznika and Tadla regions to show salt problem and its effects on potato yield limitation.

* Make a good choice of plant material adapted to salinity. This can be done by varietals trials under salt conditions.

* Make a good use of adapted N sources, by managing N fertilizers and selecting the best ones in relation to the production of high potato biomass and quality.

* Optimize N/K ratio of applied fertilizers by fertigation system under salt conditions.

* Hasten water and N efficiencies in presence of salt.

* Determine differences between salt limitations and drought effects on potato biomass, tuber quality and N-K composition of plant shoots and roots.

* Justification of the subject:

In saline Moroccan regions of Bouznika and Tadla, farmers produce high quality but low potato yields. No specific water use and fertilizer programs are followed and no adaptation of fertilization and irrigation operations is made, regarding to plant material, soil condition of salinity, organic matter composition and soil texture. Different N/K ratios are used by producers and different yields are obtanined. Field experiments and surveys are needed to optimize N/K ratios and nutrient solutions used in fertigation, to improve rhizosphere conditions by use of localized irrigation systems, pushing salt away from potato roots and to demonstrate efficient skills of conducting fetigation to farmers, helping them to choose appropriate fertigation systems (equipment and nutrient solutions) and the adequate know how.

* Methodology , Schedule of activities and research components:

+ First year:

++ Survey in Bouznika and Tadla regions to determine potato plant material used by growers, fertilizer programs adopted, N/K ratios, importance of salt problems and means of salt correction used by producers (fertigation , localized irrigation, deep plowing...)

++ Identification of experimental sites differing by salinity levels, N/K ratios of fertilizer rates, plant material and water use efficiencies.

++ National course for extension officers to make them familiar with fertigation (program as joined).

++ Training for farmers and their sons to improve their knowledge and skills in the followings:

** Installation of localized irrigation systems.

** Preparation of nutrient solutions.

** EC and pH controls of nutrient solutions.

** Fertigation piloting by EC and plant stages requirements.

** Maintenance of the equipment.

** Adaptation of injectors and dosing pumps.

2nd year:

++ Experiments 1: Tow localities (Bouznika and Tadla) x Varietals trials: 3 varieties x 3 sites by locality (salinity levels); 4 replications; Complete randomized bloc design (CRB) and classical farm cultural operations (CFCO).

++ Experiments 2: 3 sites (low, medium and high salinity levels) by locality x 2 regions (Bouznika and Tadla); different varieties, comparison of 3 different N/K ratios, CRB and CFCO.

++ Experiments 3: Trials with farm manure (organic matter), folia spray micro nutrients, soil depth of plowing...CRB and CFCO...

++ Expected results: determination of the most adapted variety (ies) to salinity and the best N/K ratio for each salinity level. Enhancement of potato productivity by cultural means in an integrated system of production and salt control.

3rd year:

++ With the best variety , the most adapted N/K ratio for each salinity level and with common cultural practices in both localities (Bouznika and Tadla) the objectives are to determine the best way to overcome salinity problems, to ovoid water stress and to pilot fertigation:

** Use of balanced nutrition.

** Tensiometry, conventional formula and balance method (80 % ETM) to pilot irrigation.

** Comparison with tow complementary irrigation (or appoint irrigation at mi growth and late tuberization stage).

** Application of previous experimental recommendations regarding salt problem overcoming.

** Demonstration to farmers and extension service.

* Expected benefits:

+ Environnemental preservation by reducing fertilizer rates and optimizing N/K ratio.

+ Potato tuber yield and quality improvement by optimizing fertigation practice and increase water and nutrient uptake efficiencies.

+ Increase of farmer's income by improving their production.

+ Improvement of extension officers and farmers knowledge and skills in matter of fertigation and balanced nutrition.

+ Valorization of saline soils of Bouznika and Tadla regions.

+ Fixation of local farmers in their land and prevention of their emigration to cities.

* Literature cited:

+ Bruns S. & Caesar K, 1990. Shoot development and tuber yield of several potato cultivars under high salt concentrations at different stages of development. Potato research, 33 (1): 23-32.

+ Casas et all, 1991. Cell growth and water relations to the halophytes in response to NaCl. Plant Cell Rep.10: 81-84.

+ Chauhan R.P.S., Singhs S.P. and Ram S., 1990. Effect of saline water on Okra and potato . Indian J.Agr. Sc. 60 (5): 350-353.

+ El Attir and Skiredj, 1998. Report of developmental project in Tadla region.

+ Gouia, 1990. Effets du chlorure de Sodium sur le transport et la réduction du nitrate chez le haricot et le cotonnier. Thèse de spécialité. Faculté des Sciences de Tunis. 170 p.

+ Greenway and Munns, 1980. Mechanisms of salt tolerance in no halophytes. Ann.Rev. Plant Physiol. 31:149-190.

+ Skiredj, El Ganga and Bekraoui, 1994 . Report on a survey about potato productivity enhancement in Bouznika region.

+ Skiredj and Cherif, 1995. Effect of cultural practices on salt correction under potato crop in Bouznika region. Memory of agronomie of the IAV Hassan II.

+ Soltani, 1988. Analyse des effets du chlorure de Sodium et des formes d'azote sur la nutrition minérale de l'orge. Thèse d'Etat. Fac. des Sc. de Tunis. 322 p.

+ Yadav B.R. and Paliwal K.V., 1990. Growing vegetables with salinity water. India Hort. 35 (3): 11-13.

* Needs equipment and consuming products:

+ IAV Hassan II laboratories are sufficiently equipped with big instruments. But carrying instruments such as powerful personal computer, pH meter, EC meter, ionometer (with all nutrient electrodes) are well recommended.

+ Consuming products such as chemicals for laboratory analyses, fertilizers, pesticides, potato seeds of various cultivars and gasoline for traveling are needed.

+ A special budget is needed to pay fees, labor , technicians making measurements , coordinator and collaborators honorarium.