a small step in improving the management and efficiency of bell pepper, and other crop cultivation, can be achieved by giving more attention to the way fertilization and irrigation are applied. at the beginning of the season, the fertilizer consumption of the plants is very low. the low quality of water and the dry hot condition at the beginning of the growing season, force the growers to irrigate more than the plants need. as a result, the irrigation and the fertilization are very inefficient. about 10-14 days after planting, when the seedlings have been established, it is possible to improve the fertilizers supply by adjusting the added amount to the field according the actual plants consumption. fertilizer excess will lead to higher levels of electrical conductivity (ec) of soil solution, resulting from the accumulation in the soil root zone. part of the accumulated nutrients in the soil at the beginning of the growing season will be available to the plants at the coming growing stages.
the absorption of the majority of nutrients in the common crops at the arava valley is characterized by the following ratio: for each 1 kg of absorbed nitrogen in the canopy and fruit, about 1.5 kg of potassium and 0.1 kg of phosphor are absorbed. data of bell pepper var maor is presented in figure 1 as an example of nutrient absorption by the plants. growing those plants in aqueous solution should require the addition of those elements to the solution at the above ratio. reducing, for example, the amount of potassium will lead to a decrease in the absorption of nitrogen, phosphor, and other essential elements for proper plants development. however, the situation is completely different for growing in the soil. the positive charged nutrient elements are absorbed in the surface of soil and clay particles. this process creates storage of potassium in the soil that can be utilized by the plants. the potassium accumulates quite rapidly when the fertilization is in excess regarding the plants needs.
in case the concentration of potassium ion in the soil solution is decreased as result of plats absorption, absorbed potassium ions are released within few minutes to the soil solution and are available to the plants.
figure 1. total yield of nitrogen, phosphor and potassium per 1000m2 of pepper plant var “maor”
the absorption rate is very high at the period of fruit setting and development. at that stage, it is necessary to add to the irrigation water (in the arava region) 40-50 gram of potassium to each 1 m3 of water.
phosphor ions react with calcium ion and create a precipitant of calcium phosphate. this reaction tack place for several hours until all the excess phosphor ions are precipitated. the natural phosphor concentration in the soil solution is around 3-4 mg/l. the high recommended concentration of phosphor in the irrigation water for fields after chemical sterilization is 30 mg/l – ten times higher than the equilibrium in the soil solution. this fertilization practice, which is necessary for the establishment of the pepper plants, creates very high phosphor storage in the soil, which can be utilized by the plants later on during the growing season.
plant water consumption is increasing from planting time (beginning of august) until the end of october. at this period the irrigation, the amount of water remains at a level of 6 mm/day. from the end of november as the days shorten and the temperature decreases, the plants and water consumption decreases as well until the end of january-mid february.
the decrease of evaporation level is compensated by the increase of canopy size and fruit setting. at that stage, the salinity of the soil solution is gradually increasing, since less water is available for proper leaching of excess salt from the active root zone. in order to maintain a stable salinity level, higher amount of water is required. higher salt content of the irrigation water (also as a result of excess fertilization) will require more water for proper salt leaching. the salinity level of the soil solution in the root zone will be derived from the water amount that is available to the farmer. in most of these situations, the impact of the increased salinity on plants development is not visible. comparison observation shows that the increased salinity reduces fruit growth rate and leads to smaller fruits.
proper planning of cultivated area size according to the available water amounts and strict fertilizer application can contribute to optimum yield and income from each growth unit.