| dc.description.abstract | Water availability, amount and distribution throughout the year is very crucial to sustained agricultural production in the water-scarce arid and semi-arid lands (ASALs). That water is scarce in the ASALs is undisputable. It is on this premise that water has been the most important and most limiting resource to agricultural productivity of Kibwezi District; mostly resulting from a combination of low and erratic rainfalls. Skillful water management is, therefore, the key to survival in these drylands. If no appropriate measures are taken, the harder and more expensive it will be to salvage the resource bases. Rainfed agriculture, consequently, need to be supplemented with irrigation to realize the potential of our soils.
Trials were conducted in Kikumbulyu location of the new Kibwezi District (Makueni County) to examine the effects of supplemental drip irrigation on growth and yield characteristics and economic feasibility on tomato (Solanum lycopersicum var. cal 1) and onion (Allium cepa L. var, red Creole). A 4-day irrigation (supplemental) interval was adopted for the research. The trials involved two modes of supplemental irrigation: twice -a-day (TI) and once-a-day (T2) water application to both tomato and onion fields, and a control (rainfed, T3). Treatments were laid out in a completely randomized block design (CRBD) with three replications.
Two seasons of tomato trials were conducted. The first experiment in 2009 coincided with onion trials. The second experiment was carried out in 2010. A total of 206.3 mm of rain was received during the first tomato season, against the total season crop requirement of 415.01 mm. In the second season, total rainfall was 328.9 mm against the crops' requirement of 394.97 mm. The supplemented amounts (for T1 and T2) were 202.76 and 207.75 mm in season 1 and, 114.15 and 126.12 mm in season 2. Onion required 390.08 mm, but only 234.8 of rainfall was received during the growth period. T1 and T2 plots were thus supplemented with 182.8 and 184.74 mm, respectively.
For tomato season 1 and 2, the measurable parameters (plant height, numbers of leaves and numbers of branches per plant) were monitored at three stages; flowering, fruit setting and maturity. The same parameters, except number of branches, were monitored in onion at 30, 60, and 90 days after transplanting (DAT). These parameters responded positively to the supplemental irrigation in both onion and tomato. There were significant differences (p ~ 0.05) in the growth characteristics of T1 and T2 plots when compared to those of T3.
Supplemental irrigation also had a remarkable effect on increasing crop yields based on the fruitfbulb yield analysis for the two crops. When compared to T3, T1 and T2, respectively, represented a 78.91 % and 63.14% increase in tomato (season 1) marketable yields. The effect of supplemental irrigation over rainfed agriculture was even more outstanding on onion, resulting to a yield increase of 153.16% and 137.97% in T1 and T2 plots, respectively. Onion water use efficiency increased with increasing water application, with the results obtained in T1 and T2being significantly higher (p ~ 0.05) and different from those ofT3. However, tomato results showed a deviation from this trend; irrigated treatments T1 and T2 had significantly lower WUE compared to T3.
The trials' results for both crops also demonstrated that the twice-a-day supplemental irrigation mode at 4-day interval (T1) was comparatively effective in enhancing yields than supplementing at once-every-day (T2). When the gross margin analysis was carried out for the supplemental irrigation system (SI) and compared to the current rainfed agriculture, it could be adduced from the results that potentially higher benefits in terms of yield increases can be obtained through the combination of supplemental irrigation and other appropriate agronomic practices specific to the crops grown. The yield increases for both crops with supplemental irrigation alone was sufficient to compensate for the investment of input and capital in the system.
Since the current rainfed production system would most definitely result into an economic loss to the farmers, it would be wiser to encourage farmers to invest in supplemental irrigation as a means to cushion against losses. What are needed are efforts towards enhancing farmers' willingness to act with self-interest towards its adoption. It would also be more prudent if vigorous rural extension services were initiated to encourage culture change among small-scale farmers so that they can shift to growing high value crops like tomato and onions, as opposed to traditionally grown low-yielding crops like maize. Supplemental irrigation, in general, requires that the crop be of high value in order to pay for the extra investment. | en_US |
