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”.
This material content is developed to serve as a GUIDE for students to conduct academic research
EFFECTS OF SAWAH WATER MANAGEMENT SYSTEMS ON SOIL PROPERTIES AND RICE GRAIN YIELD IN EBONYI STATE SOUTHEASTERN NIGERIA>
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