Rice from Asia was first introduced in Kenya in 1907 and is the third most important cereal crop after maize and wheat. Despite the annual increase in rice consumption at a rate of 1% in Kenya, production of rice has not managed to keep up with consumption as it has been fluctuating in the past 20 years between 45,000 and 80,000 tons per year. This forces Kenya to import rice annually because the national rice consumption is estimated to be 300,000 tons [1
]. Rice production in Kenya between 2014–2018 stood at 3.84 tons/ha [2
In Kenya, 80% of rice is grown in irrigation schemes. There are more than 3000 existing small-holder irrigation schemes in Mwea, Bunyala, Ahero, Kano, Msabweni, Maugo and Tana deltas among other areas where rice is grown for food and commercial purposes [1
]. This shows that small-holder farmers are vital for Kenya’s agriculture and rural economy, as is the case in India [3
]. Small-holder farmers in Kenya farm smaller pieces of land, with a sizes 0.47 hectares [4
]. Maugo Irrigation Scheme is managed by Maugo Rice Farmers Co-operative Society. The scheme is a gravity-operated scheme and is located in Homa Bay county, Kenya. It was started by farmer’s initiatives in the year 1962 using flood water from River Maugo for subsistence. Land sizes in the scheme are small and measure 40 m by 100 m and are ploughed using different techniques [1
Small-holder farmers use hand held hoe, ox and tractor for ploughing. These ploughing techniques have their own unique challenges. All families own two to three hoes; however, during ploughing when more hoes are needed, some homesteads borrow these from their neighbors. Borrowing of hoes can delay ploughing if neighbors are using them at the same time. Oxen for ploughing can be owned by the farmer or hired from another farmer. During ploughing, the demand for oxen goes up, while some farmers are left behind. Many tractors ploughing fields are mainly hired from the rich farmers from the neighborhood, but they are expensive [1
] and out of reach for poor farmers. The majority of these tractors are old and inefficient, thus resulting in the emission of greenhouse gases (GHGs) through the consumption of fossil fuels [5
]. All the challenges end up delaying ploughing and thereby affecting crop production. Poor and untimely land preparation cause serious weed problems and expose plants to harmful substances such as carbon dioxide and butyric acid released by decaying organic matter in the soil [6
]. When not done properly, ploughing results in unevenness of the paddy field, resulting in the uneven growth of rice and thus reduced yield.
Depth of ploughing depends on the type of tool used. Hand hoe ploughing depths are 10 cm and can be repeated to achieve deeper depths. Animal drawn ploughs, like ox-plough, plough to a depth of 15 cm. Disc plough attached to tractors can plough to greater depths, such as 30 cm [7
]. Recommended depths of ploughing for rice are 15–20 cm. Deep ploughing should be discouraged because deeper ploughing moves the fertile soil deeper and hence unavailable for rice growth [8
]. Ploughing is followed by harrowing and then levelling before transplanting seedlings. Ploughing and harrowing in water is known as puddling. Puddling makes the soil not lose water by deep percolation. Experiments on rice have shown that tillage has greater effects on yields than irrigation. Ploughing to recommended depth can be one way in which the Kenyan government can increase annual production of rice from 70,000 tons in 2018 to 406, 456 tons by the year 2022 [9
]. Tillage to depths of 20–25 cm favors root development and uptake of minerals and hence higher yields of 5.82 tons/hectare could be achieved [10
Farmers in Maugo Rice Irrigation Scheme barely subsist as they are stuck in the poverty cycle. Most of these farmers cannot access credit from commercial banks as the majority of them (48%) do not have title deeds for their farms [11
]. Hence, these farmers, like other small-holder farmers, face myriad of challenges like human capital, infrastructure for ploughing, irrigation water [12
], among other problems like climate change. This calls for a study on water management at the farmers level with a view to saving water, which is a priority for any farmer. As climate change is expected to reduce rice yields by 10% in the 21st century [13
], farmers need to be taught methods of saving water for them to be able to cope with water challenges in the future. Farmers in Maugo area do not plough dry soil, rather they add some water to make it soft. Addition of this water helps in ploughing, but will not contribute to crop development. Ploughing dry soil helps to save water [14
], but results in decreased yields. Saving of water will address the water problem particularly in areas where canals are not working effectively and low water flows in rivers that are normally observed in the study area during dry months [11
]. This will further give information on the performance of dry-seeded rice [15
]. Some literature [16
] has focused on the system of rice intensification on large scale and not small-holder farmers, which are key to rice production in Kenya. Understanding local practices done by small scale farmers has generated plenty of research interest and thus requires attention and further scrutiny. Pesticide application practices and knowledge of small-scale farmers was done by Ndayambaje et al. 2019 [17
] in Rwanda.
Land preparation techniques may influence water retention and yields of rice. Zero-tillage is considered to be the best alternative to ploughing and harrowing due to its effect on soil properties, but ploughing, harrowing and levelling increases rice yield and reduces weed density. Indeed, most developing countries like Kenya have not benefitted from the awareness of zero-tillage [18
]. Information of the effect of different land preparation techniques on water retention and rice yields in smallholder irrigation schemes like Maugo Irrigation scheme is scanty. While many studies have proposed ways of improving water management, little is known about the performance of smallholder farmers’ ploughing technique practices and other ploughing practices in reducing water use in rice growing. This research highlights the need for farmers to slowly learn new ways to improve their technical know-how on water management by setting up experiments near them.
The objective of this study was to compare water retention and rice yield at a farmer’s plot using conventional tillage of wetting before ploughing and ploughing without wetting using hand hoe, oxen and tractor as ploughing techniques.
Tractor ploughed plots had the highest number of tillers owing to its greater depths. The slow increase of tillers between week 2 and week 11 for hand ploughed fields could be attributed to shallow depths for hand hoe ploughing. The maximum number of tillers observed in day 77 was consistent with modern day rice varieties that have 20–25 tillers [20
]. Tractor ploughing had highest depth due to the increasing intensity of tillage. This means that, with greater depths, came adequate aeration for the growth of rice. Increase in root volume means an increase in nutrient uptake by the root, which led to high yields. All the rooting depths were higher than 45 cm observed for well-watered rice varieties in Malaysia [21
] and more than double of what was observed in Taiwan [22
The amount of water used during land preparation was close to 360 mm observed by Singh, et al. 2001 [23
]. The highest consumption of water in a conventional way was attributed to the water that was used to wet the fields before ploughing. The second highest value for tractor ploughing was linked to deeper depths of ploughing when tractors were used. The observed least amount of water consumed by ox-plough without wetting was linked to shallow depths of ploughing because the soils were hard to plough. From the results, farmers were able to appreciate the need for not wetting the field, thus avoiding wastage of scarce water resources. The labor that would have been used during wetting the field before ploughing could be used elsewhere.
Conventional ox-ploughing resulted in a significantly lower mean yield of 4.7 tons/ha. This agrees with Huang et al. study [12
] that found that deep tillage had more yield than shallow tillage. Use of the hand hoe ploughing technique increased yields by 20 percent of the conventional ox-ploughing. Yields for tractor ploughing and hand hoe ploughing were also close to 5.5 tons/ha observed by FAO (2020) [13
]. All the yields were well above the average of 3.84 tons/ha [8
], but they were half of the potential yields of 10 to 11 tons/ha for low-land rice when water is not limiting [24
]. Furthermore, the observed yields were below 7.4 tons/ha for USA, however, the yields were closer to 6.19 tons/ha in China [24
]. This shows that there is still a need for improvement in rice production in the area of study. These WUE were similar to rice production in Pakistan, which has a WUE less than 0.45 kg/m3
Another way of increasing yields and water use efficiency can be done by using biochar, as was observed in China [26
]. The reason why hand hoe performed better than all the other techniques could be attributed to the reason that hand levelling and harrowing was done by hand. While hand hoe had the highest WUE, it is a laborious job and time consuming. Hand hoe ploughing is impractical for larger fields, but since farmers have small pieces of land, they are recommended because they create jobs for youth and do not pollute the environment like tractors. Engine of tractors use diesel, fossil fuel, which produces carbon dioxide when the tractor is ploughing. Carbon dioxide is one of the greenhouse gases that contribute to global warming, as observed by Mamona et al. [5
]. This is welcome as the County Government of Homabay in the area has a labor force that is 48% of the population. In fact, this could assist in alleviating the rate of unemployment in the county, which stood at 73% [14
]. Use of hand hoe ploughing is encouraged, as there was not much benefit in using tractor ploughing followed by subsequent harrowing and levelling manually. Thus, the study therefore encourages that hand hoe preparation techniques be used for water saving, better yields and job creation purposes. From the study, it can be seen that partial mechanization is not advantageous. The study looked at reducing the usage of irrigation water, which is a scarce resource in the world [27
] and this renewable resource is expected to reduce in future [28
] and not water quality. Environmental degradation in the area means high morbidity of water pollutants [14
]. Since the water for irrigation comes from the river, it is suspected as having some heavy metals, as seen in Yangtze river in China [29
] or emerging pollutants in drinking water resources [30
], which can pose serious health risks and needs more research in the future.