沙漠研究 19-1, 309- 312 (2009 )Journal of Arid Land Studies“Desert Technology IX ”
Refereed Paper

Study on Stable Mulching as Effective Water Saving Practice
Yuzo KOBAYASHI1, Shoko YATO2, Tomonori FUJIKAWA2, Takahiko NAKAMURA2,
Machito MIHARA2, Masaharu KOMAMURA2
Abstract: Under limited precipitation in Sub Saharan Africa, soil water is the key factor for
growing crops. As covering soil surface with organic materials, stable mulching is expected tobe beneficial for agriculture in such arid and semi-arid areas. The objective of this study is toevaluate the water saving effect of stable mulching (sorghum stalk residues or lumber chips).
Results showed that evaporation in mulched plots were smaller than that in irrigated plots andthe soil water content tended to increase slightly with time. The average plant length and fresh
weight of these mulching plots were better than those of non-mulched plot.
Keywords: Stable mulching, Sub Saharan Africa, TDR, Water saving

1. Introduction
Sub Saharan Africa (SSA) includes many developing countries and has been marked by rapid
population growth and affected by severe desertificationA). Regarding agriculture, “water” and “soilfertility” are absolutely insufficient. Mulching of the soil surface controls the evaporation in area having
little effective rainfall. Unfortunately at SSA, it is difficult to obtain mulching materials from outside.
So, for improving agricultural environment in SSA, this study dealt with the stable mulching, the organicmaterials obtained from farmlands, as an effective water saving practice. According to former researchstudies (Silvakumar and Salaam, 1999, Hayashi et al., 2008), attention has been paid mostly to the effect ofthe crop residues on soil fertility improvement. For making clear the water saving effect of stablemulching, cultivation tests were conducted in this study. Furthermore, the effect of stable mulching onplant growth was investigated, as the stable mulching was expected also to supply nutrients to the soil.
2. Materials and Methods
The experiment was carried out at the greenhouse of Tokyo University of Agriculture, Japan, from June
to November, 2008. Upland rice was cultivated at each plot of 6.5 m long and 0.8 m wide. Six plots weredivided into 2 groups based on the amounts of irrigation; one was irrigated at 3 to 6 mm/day (Standard plot)
and the other at 1.5 to 3 mm/day (1/2 water saving plot). Each group was constituted with 3 different
treatments, as mulching with sorghum stalk residues (SSR, Fig. 1), lumber chips (LC, Fig. 2) andnon-mulching (NM). The schematic diagram of the cultivation experiments are as follows in Figure 3.
After the upland rice germinated, SSR was cut at 20 to 30 cm in length and arranged in the plot(thickness was 3 cm approximately). And LC was also arranged at 3 cm × 3 cm × 0.5 cm (approximatelyFig. 1. SSR mulching.

12Fig. 2. LC mulching.

Graduate School of Agriculture, Tokyo University of Agriculture, Japan.
Faculty of Regional Environment Science, Tokyo University of Agriculture, Japan.

310

Fig. 3. Schematic diagram of the cultivation experiments.

1-3 cm in thickness). The irrigation amount ofstandard plot was decided referring to theprecipitation of the Atsugi farm, Tokyo
University of Agriculture located in Atsugi City
near Tokyo. The amount of other water saving
plot was referred the precipitation of the rainyseason in Niamey, Niger.
Soil moisture was measured at 1 hourinterval by SMART- Enviro (Sentek Pty, Ltd.
Australia)B), that has 5 TDR sensors (5 cm, 15 cm,25 cm, 35 cm and 45 cm depth) as shown in
Figure 4 (Sentek Pty, Ltd. 2005). The growthof cultivated crops was measured by plant length(43 days after the sowing date), heading rate (at82 days) and fresh weight of harvesting stage ateach plot.

Fig. 4. Outline of the soil moisture measurement system.

3. Results and Discussion
The experimental results of the NM atstandard plot showed that water content at 5 to 15cm deep from soil surface increased sharply, andthen gradually decreased with time after theDepth:
5cm
15cm
25cm
35cm
45cm
irrigation (Fig. 5).
It took only 18 hours toFig. 5. Water content of NM at standard plot.
return same water content as that before theirrigation.
Also more than 10% of volumetricwater content decreased in a day.
On the other hand, at deeper layers, changes in the water content were delayed and small. In the NMplot, water contents tended to decrease with time which indicated that evaporation exceeded the amounts ofthe irrigation. However, the decrease in soil water content in the SSR or LC plots after the irrigation was311(A) 5 cm(B) 15 cm(C) 25 cm(D) 35cm

NM plot

SSR plot

LC plot

Fig. 6. Water content at different soil depths and treatments.

remarkably slower comparing to NM plot (Fig. 6).
This result suggested that the amounts of evaporation
became less in the SSR or LC plots, as the water content
tended to increase even in the relatively shallow layer (e.g.
15 cm depth at LC plot and 25 cm depth at SSR plot).
Especially in the plots applied mulching with SSR, watercontents at the depth lower than 25 cm were steady with anincreasing tendency. As mulching with SSR or LC worked
well for reducing evaporation, it was concluded that stablemulching was effective as a water saving practice.
Regarding the growth of the upland rice on standard
plot, the effect of mulching with SSR and/or LC on both
early growth and heading promotion was remarkably
noticed. After 43 days from sowing, the average plant
lengths are significantly different between standard and 1/2
water saving plots also among three treatments: 64.2 cm and44.2 cm ( SSR mulch ), 57.1 cm and 45.7 cm (LC mulch)and 56.4 cm 39.5 cm (no mulch), respectively (Fig. 7). In
standard plot, the heading rates at 82 days after sowing were66% at SSR and 60% at LC higher than that of NM (45%,Fig. 8). However, regarding to the plant length and fresh
weight of harvesting time (140 days after sowing) instandard plots, the average plant length and fresh weight at
NM plot could be better than those at SSR and LC (Fig. 9).
It was considered that a small evaporation caused excessive
soil moisture in SSR or LC. The effect of the growthpromotion due to mulching appeared remarkably in watersaving plots (Fig. 10). The control of evaporation withmulching worked well for the growth of upland rice with

Fig. 7. Average plant lengths (43 days).

Fig. 8. Heading rate (82 days).
Note: Rice of water saving plot hadn’t done
heading yet.

312

Fig. 9. Result of grown rice at standard plot.

Fig. 10. Result of grown rice at 1/2 water saving plot.

preventing water shortage. According to these results, it was concluded the stable mulching was effective
for the plant growth as a water saving practice in SSA.
4. Conclusions
In the plots applied mulching with sorghum stalk residues (SSR) or lumber chips (LC), the amountsof evaporation were smaller than those of the irrigation, and then water content in deeper layers tended toincrease slightly with time. Especially in the plots applied mulching with SSR, water content at the depth
lower than 25 cm were steady with an increasing tendency. It was concluded that stable mulching waseffective as a water saving practice.
However, regarding the growth of the upland rice in standard plots, the average plant length and fresh
weight at NM plot were better than that at SSR and LC. It was considered that a small evaporation caused
excessive soil moisture in SSR or LC. The effect of the growth promotion due to mulching appeared
remarkably in water saving plots. The control of evaporation with mulching worked well for the growthof upland rice with preventing water shortage. According to these results, it was concluded the stablemulching was effective for the plant growth as a water saving practice in SSA.
AnnotationA) FAO Hunger map of 2008, http://www.fao.org/es/ess/faostat/foodsecurity/FSMap/map14.htm, FAOSTAT.
B) SMART-Enviro (Sentek Pty, Ltd. Australia), Japanese edition manual, TWC, Tokyo, January 2005.
References
Hayashi K., Abdoulaye T., Gerard B., Bationo A. (2008): Evaluation of application timing in fertilizer micro-dosing technology onmillet production in Niger, West Africa. Nutr CyLCing Agroecosyst, 80: 257-265.
Silvakumar M.V.K., Salaam S.A. (1999): Effect of year and fertilizer on water-use efficiency of pearl millet (Pennisetum glaucum) in
Niger. Journal of Agricultural Science, 132: 139-148.