EFFECTS OF SAWAH WATER MANAGEMENT SYSTEMS ON SOIL PROPERTIES AND RICE GRAIN YIELD IN EBONYI STATE SOUTHEASTERN NIGERIA

ABSTRACT

In an attempt  to replicate  the successful  Japanese  Satoyama  watershed  management model  in  the  African  agro-ecosystems,  sawah  rice  cultivation  technology  has  been introduced to West Africa in the last two decades. This study was conducted in inland valley at two different locations (Akaeze and Ikwo), to  evaluate the effects of sawah water management systems on soil properties and rice grain yield. A split-split-plot in a randomized  complete  block design  was  used  to  evaluate  these  three  factors  (sawah types, growing environments and soil amendments) as they affect the soil properties of these two locations and the grain yield of rice as a test crop. Three sawah types and four rice growing environments  were used in each of the two locations and they included; rain-fed  sawah,  spring  type  and  pump  type.  The  rice  growing  environments  are; complete sawah– bunded, puddled and leveled rice field (CS); farmers environment- no bunding  and  leveling  rice  field  (FE);  incomplete  sawah-  bundding  with  minimum leveling and puddling rice field (ICS) and partial sawah– after bunding, no puddling and leveling  rice  field  (PS).  There  were  five  levels  of manure  application,  which  were replicated three times and these included; rice husk at 10 ton/ha; rice husk  ash at 10 ton/ha; poultry droppings at 10 ton/ha; N. P. K. 20: 10: 10 at 400kg/ha and the control (Zero application).  The study was undertaken in 3 cropping  seasons  (2008, 2009 and

2010) using the same watershed and treatments. The treatments were applied annually, but the effects of additive residual effects of the amendments were not  studied in the course of this research. At the end of each harvest, the soil physical properties analyzed for included; soil BD, total porosity,  water stable aggregates,  mean weight diameter, water  retention  and  saturated  hydraulic  conductivity.  While  that  of  soil  chemical

properties included; soil pH, OC, total nitrogen, exchangeable bases (Na+, Ca2+,  Mg2+

and  K+).  Others  included  CEC,  exchangeable  acidity,  base  saturation  and  available phosphorous, while the rice grain yields was measured. The results showed that the soil

pH, organic carbon (OC) and total nitrogen (TN) were significantly improved by sawah types in all the studied soils. At Akaeze pH measured in water varied from 3.8 to 3.9, 4.3 to 4.5 and 4.5 to 4.6 in the first, second and third year (rain-fed to spring sawah type), respectively. The Ikwo soil showed pH mean values of 3.6 to 3.7, 4.4 to 4.6 and 4.6 to

4.8 in the 1st, 2nd  and 3rd  year of planting, ranging from rain-fed to spring sawah type, respectively. These parameters (pH, OC and TN) were also improved statistically upon

by the different growing environments in different ways. The pH at Akaeze varied from

3.9 to 4.0, 4.2 to 4.4 and 4.5 to 4.8 in 1, 2 and 3rd year of study, ranging from farmers’ to complete sawah growing environment. The pH changed from 3.5 to 3.7, 4.3 to 4.6 and

4.5 to 4.9 within the three years of study and from farmers’ to complete sawah growing environment in Ikwo location. Also, the amendments equally positively influenced these parameters in the two locations. The SOC values in Akaeze location ranged from 1.05 to

1.14% (pumping to rain-fed) in the first year, 1.09 to 1.26% (pumping to spring sawah type) in the second year and 1.10 to 1.27% (pumping to spring sawah type) in the third year. In Ikwo location it ranged from 0.84 to 1.02% in the first year, 0.91 to 1.10% and

0.94  to  1.14%  in  the  second  and  third  year  from  rain-fed  to  spring  sawah  type, respectively.  The  exchangeable  bases were also  positively  statistically  influenced  by these three factors tested and their interactions in both locations in most years of study. The results indicated that the CEC was positively improved by sawah types, growing environments and amendments in different forms in second and third years of study in both locations. The range values for growing environments in Akaeze varied positively

(P<0.05) from 5.60 to6.31 cmolkg-1  for the 1st  year, 5.44 to 10.70 cmolkg-1  (farmers’ to

complete sawah environment), and 5.52 to 9.34 cmolkg-1  (farmers’ to complete sawah

growing  environment),  in the 2nd   and  3rd  year,  respectively.  The mean values  Ikwo location ranged from 9.56 to 10.89 cmolkg-1 in the 1st  year, 10.17 to 12.73 cmolkg-1 and

10.61 to 13.24 cmolkg-1, in the 2nd  and 3rd  year, respectively. The results showed  that

poultry droppings significantly improved the CEC higher within the periods under study in the two  locations.  The mean values  of CEC in Akaeze  varied  from 4.18  to 6.83

cmolkg-1, 3.92 to 10.86 cmolkg-1  and 3.78 to 9.15 cmolkg-1, in the 1st, 2nd and 3rd  year of study. The mean values of CEC for the periods under study ranged from 7.36 to 11.27 cmolkg-1, 7.64 to 13.09 cmolkg-1  and 7.85 to 13.74 cmolkg-1  for the 1st, 2nd and 3rd year. The EA was also significantly reduced by these factors in both second and third years of

study in Akaeze,  whereas  in Ikwo  location,  the  soil  EA  was  positively  statistically reduced by these factors for the three years of study. The EA on the 3rd  year varied from

2.39 to 2.99 cmolkg-1, (complete to farmers’ growing environment) in Ikwo soils, while in Akaeze,  it varied from 2.99 to 3.07 cmolkg-1, (partial to complete  growing sawah

growing environment)  on the same 3rd  year of study. The available phosphorous  was significantly improved by these three factors and their various interaction forms in both

second  and  third  year  of study in the two  locations.  In the  same  manner,  the  base saturation was affected in most years of study by the studied factors and their  various forms of interactions. The soil bulk density (BD) was significantly reduced  differently by sawah types; growing environments and soil amendments in both sites in the three years  of  study.  It  was  observed  that  the  interactions  of  sawah  types  and  growing environments;  sawah  types,  growing  environments  and  amendments  did  positively (P<0.05) reduced the soil BD of Ikwo soils for the second and third year period of study, while in Akaeze site, it was the interaction of sawah types and growing environments only that did positively reduce the soil BD in the first and second year of study. The total porosity was also improved in the same periods of study in both locations by the studied three factors and their  interactions. The water stable aggregate (WSA), water retention (WR) and saturated hydraulic conductivity (Ksat) were also significantly improved upon in different forms by the three factors and their various forms of interactions. The effects of  sawah  water types was observed  to have significantly (P<0.05) improved  the rice grain yield. The mean grain yield values in Akaeze ranged from 2.87 – 3.54 t/ha, in the first year, 3.63 – 4.03 t/ha in the second year and 4.23- 5.00 t/ha in the third  year of planting. The mean grain yield values in Ikwo varied positively (P<0.05)  from 3.38 –

3.73 t/ha in the first year, 5.12 – 5.67 t/ha in the second year and 5.39 – 6.28 t/ha in the

third year of planting with the spring sawah type yielding higher. It was also  obtained that all the sawah growing environments positively improved the grain yield relatively higher  than  the  farmers’  growing  environment.  The  mean  values  in  Akaeze  varied

positively (P< 0.05) from 2.55 – 3.92 t/ha, 3.16 – 4.46 t/ha and 4.03 – 5.00 t/ha in the 1st,

2nd  and 3rd  year of planting, respectively. In Ikwo site, it ranged from 3.19 – 3.84 t/ha,

4.84 – 5.86 t/ha and 5.28 – 5.94 t/ha in the first, second  and third year of  planting, respectively,   with   complete   giving   higher   yield   in   both   locations   than   other environments.  It  was  generally  observed  that  plots  amended  with  poultry  dropping significantly (P< 0.05) increased  the grain yield in both  locations in the whole three years of the study. The results from Akaeze location showed the range mean values of the rice as; 1.71 to 4.04 t/ha in the first year, 1.61 to 4.59 t/ha in the second year and 1.78 to 5.52 t/ha in the third year of planting. Also in Ikwo location, the values varied from

1.87 – 4.12 t/ha, 1.98 – 6.78 t/ha and 2.09 – 6.75 t/ha in the 1st, 2nd  and 3rd  year  of

planting, respectively. The combination of sawah management and amendment practices improved the soil properties and rice grain yield significantly (p < 0.05) in most of the years in both locations.

CHAPTER ONE

1.0                                               INTRODUCTION

Increasing rice production both to meet the country’s food requirements and to help the world overcome food crisis is one major issue facing Nigeria today. Nigeria is now one of the largest food importers in the world. In 2010 alone, Nigeria spent 356 billion naira on importation of rice. Nigeria is eating beyond its means. While we all smile as we eat rice  everyday,  Nigerian  rice  farmers  cry  as  the  importations  undermine  domestic production  (Adesina,   2012).  Given  the  size  and  value  of   the  imports,  there  is considerable political interest in reducing rice imports.

The Nigerian government has the objective of self-sufficiency in rice high on the agenda

– witness the previous import ban, the stated goals of the Presidential Committee on rice and the current effective duty on imported rice.

Rice is unique among the major food crops in its ability to grow in a wide range  of hydrological situations, soil types, and climates. Rice is the only cereal that can grow in wetland  conditions.  Depending  on  the  hydrology  of  where  rice  is  grown,  the  rice environment  can be classified  into irrigated  lowland  rice, rained  lowland  rice, flood- prone rice, and upland rice (Maclean et al 2002 and Bauman et al., 2007a).

Agricultural productivity in Nigeria and other West African countries fluctuates, mainly because the countries’ agriculture is rain-fed and subsistence farmers rely on the rain as the main backbone of farming in these countries. However, Nigeria is relatively blessed with rain; its problem is how to secure adequate water in the dry season since rain falls much more in the rainy season. Nigeria has continued irrigation projects for the purpose of using her river water but these projects are still few in number. Thus, considering its rainfall  and  river  discharge,  the  country  has  a  fairly  high  potential  for  irrigation development. Its irrigated area was estimated at 233,000 ha in 1998; the largest in West Africa, but the percentage of irrigated  area is as low as 0.8% (Hirose and Wakatsuki,

2002).

Fortunately,  these  inland  valleys  or  floodplains,  which  have  specific  hydrological conditions and have been cited as having high potential for the  development of rice- based smallholder  farming systems at village levels, occur  abundantly in Nigeria and other West African Sub-region in general (Moormann,  1985; Wakatsuki,  et al; 1989; Windmeijer  and  Andriesel  1993;  Otoo  and  Asubonteng,  1995). Maintenance  of soil

fertility, weed and water control is major constraints to utilization of these inland valleys for sustainable rice based cropping (Otoo and Asubonteng 1995). In order to overcome such difficulties and for effective and sustainable crop production in inland valleys of Sub-Sahara Africa (SSA), new farming system(s) that can restore and enrich poor soils must be developed

(Barrera-Bassols  and Zinck, 2000; Kamidouzono et al; 2001 a and b). For sustainable increase  to  cope  with  present  population  expansion,  the  African  adaptive  Sawah- lowland   farming,   with   small   scale   irrigation   scheme   for   integrated   watershed management, will be the most promising strategy to increase sustainable food production and at the same time to restore degraded watersheds in tropical areas, especially in Sub- Sahara Africa (SSA) (Hirose and Wakatsuki, 2002; Hayashi and Wakatsuki, 2002).

The term  “Sawah”  refers  to leveled  rice field  surrounded  by bunds with inlets  and outlets for irrigation and drainage. The term originated from  Malayo-Indonesian.  The English term, paddy or paddi, also originated from the Malayo-Indonesian term, paddi, which means rice plant. The term, paddy, refers to rice grain with husk in West Africa. Paddy field is almost equivalent to Sawah for Asian Scientists. However, the term paddy field only refers to just a rice field including upland rice field in West Africa. Therefore, in order to avoid confusion between the terms rice plant, paddy and the improved man- made rice growing environment, the project proposed to use the term Sawah (Hirose and Wakatsuki, 2002).

Sawah is an environmentally creative technology that restores ecological environments as it is characterized  by replenishing mechanisms with intrinsic  resistance to erosion. Geological fertilization is due to flooding and compensates for the losses of nutrients and can only be realized in lowland sawah-based rice production (Wakatsuki, 1994; Kyuma and Wakatsuki, 1995; Wakatsuki, 2004). Adoption of these Sawah systems could help improve the fertility status of soils, water and weed control (Asubonteng et al; 2001).

It is well-known that weeds can be controlled by means of water control. Levels of N- fixation under submerged Sawah systems reach up to 20- 100 kg/ha/year in Japan and up to 20-200 kg/ha/year  in the tropics depending on the level of soil fertility and water management (Hirose and Wakatsuki, 2002; Kyuma, 2003). This amount is comparable with the nitrogen fixation amount of leguminous plants. Rain-fed upland farming has no such  option  but  rely  on  the  use  of  leguminous  plants,  animal  dung,  other  organic fertilizer, and /or chemical fertilizer.

Under  submerged  condition,  because  of  reduction  of  ferric  iron  to  ferrous  iron, phosphorous availability is increased and acid pH is neutralized, hence  micronutrients availability is also increased (Kyuma, 2003). These eutrophication mechanisms are not only encouraging the growth of rice plant but also encourage the growth of various algae that increase the nitrogen fixation (Wakatsuki and Masunaga, 2006).

Under nitrate rich submerged water conditions, sawah systems encourage denitrification; easily   decomposable   organic   matter   becomes   substrate   of   various   denitrifyers. Purification of the nitrate polluted water is another function of sawah system (Wakatsuki

2002, Kyuma 2003).

Traditional water management systems are characterized by the fact that they focus on storage of water in the rice field, without any possibility to divert water from one place to another. Famers make straight bunds across the valley bottom to store water in the fields. The lowlands are often slightly concave; these straight bunds result in deep water- storage in the lowest parts of the lowland, and hardly any  flooding near the fringes. These traditional practices usually lead to differences in rice performance and yield from the same field, and large disparity in soil characteristics of the same field. The above observed problems led to this study.

The major objective of the study was to compare the various sawah water management systems in two different locations as they affect soil characteristics and rice yield.

The specific objectives were to:

* determine changes in soil characteristics and crop yield due to sawah type.

* compare the soil characteristics and rice  grain yield as affected by growing environments.

*  evaluate the contributions of different manure types on soil properties and grain yield, and

*  determine the interaction effect of the factors on soil properties and rice

grain yield.

Significance/Justification of the Study

The study addresses the issue of fluctuations in agriculture and increased importation of rice. Farmers will realize the level of loses in yield due to total dependence of rainfall for their rice production. Commercial rice farmers will as well learn the  modern ways of field water and nutrients management that are environmentally friendly and sound for

increasing and sustainable rice production in Nigeria. Rice growers can take precautions on how to  use water  wisely  and  reduce  water  losses  from  rice  fields through  land preparation which lays the foundation for the whole cropping season and it is important in any situation to “get the basics right”.

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