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Rice

Performance of Upland Rice Fitted into Lowland Rice–Vegetable/Cowpea Sequence in Rainfed Inland Valley

^a Dep. of Plant Physiology and Crop Production, College of Plant Science and Crop Production, Univ. of Agriculture, Abeokuta
^b Dep. of Plant Breeding and Seed Technology, College of Plant Science and Crop Production, Univ. of Agriculture, Abeokuta

^* Corresponding author (sundayadigbo{at}yahoo.com)

Received for publication June 7, 2005.

	ABSTRACT

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSION REFERENCES

 
The inland valleys (IVs) have the potential of growing three crops in sequence within a year without supplemental irrigation. Considerable opportunity exists for growing the third crop between main crop and dry season cropping. This is a niche that has not been exploited. Field experiments were conducted at the University of Agriculture, Abeokuta, Nigeria in 2000–2003 to determine the growth and yield performance of upland rice (Oryza sativa L.) in lowland rice–upland rice–fallow, lowland rice–upland rice–cowpea [Vigna unguculata (L.) Walp], and lowland rice–upland rice–vegetable sequences in an IV. Lowland rice–upland rice–fallow, lowland rice–upland rice–cowpea, lowland rice–upland rice–okra (Abelmoschus esculentus L.), lowland rice–upland rice–amaranth (Amaranth cruentus), lowland rice–fallow–fallow, lowland rice–fallow–cowpea, lowland rice–fallow–okra, and lowland rice–fallow–amaranth sequences, which ran concurrently constituted a cropping cycle. The first, second, and third crops in all the cropping cycles were planted in May, October and January, respectively. The grain yields of preceding lowland rice in the various sequences with or without upland rice were similar. The preceding lowland rice variety BW 311-9 enhanced the height and grain yield performance of upland rice. The grain yields of the two upland rice varieties in the existing niche were similar in the three-crop sequence but substantially lower than the obtainable yield in an upland ecology. Upland rice crop could be grown in between the lowland rice and vegetable/cowpea without reducing the yields of lowland rice and vegetable. Inclusion of upland rice in the sequence decreased the overall benefit/cost ratio of triple cropping. Thus, two-crop sequence, which is currently being practiced by the traditional farmers, should be adhered to, until a suitable crop or technology is identified.

Abbreviations: DAP, days after planting • DMRT, Duncan Multiple Range Test • IV, inland valleys •

	INTRODUCTION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSION REFERENCES

 
INLAND VALLEYS occur all over West Africa, where valley bottoms and hydromorphic fringes are estimated to occupy between 22 and 52 million ha of land (Windmeijer and Andriesse, 1993). Inland valley is known to have considerable potential for intensification and sustainable land use (Izac et al., 1991; Windmeijer and Andriesse, 1993). However, the IVs are only marginally used. In most areas, the valley bottom offers the only possibility for dry season cropping of dry land crops (Carsky and Ajayi, 1992). Increased sustainable cultivation of IVs, which generally have more fertile soils and more available water than the adjacent uplands, promises to relieve the pressure on overexploited upland soils while adding significantly to Central and West African food production (IITA, 1990). The potential impact of IVs is related to the presence of water and large areas covered. Therefore, to increase the production of rice, vegetable and other upland crops, intensified use of the IVs is inevitable.

Under traditional farming, one crop of rice is grown per year because swamps are not developed and water flow is not controlled (WARDA, 1993). In Nigeria, some farmers grow one single crop of lowland rice (lowland rice–fallow–fallow) in the main season and abandon the IVs until the following year. Most farmers practice double cropping in the IVs. That is, lowland rice is planted in the main cropping season between April and May when the rains have become steady and is harvested in August and September depending on the length of maturity of the variety. The IVs are then allowed to drain until such a time when the land is no longer saturated and will support upland crop, such as vegetables or maize (Zea mays L.) during the dry season (lowland rice–fallow–vegetable sequence).

Considerable opportunity exists for growing the third crop between the main crop (lowland rice) and the dry season cropping. This is a niche that has not been exploited. This niche is too short to accommodate another lowland rice crop. Moreover, the available moisture may not be sufficient to support a lowland rice crop. Early maturing upland rice could be used due to its short growth period. Furthermore, soil moisture regime could be sufficient to sustain such crop.

With the growth of urban population in Nigeria, rice consumption has surpassed its production. Rice production in Nigeria between 2001 and 2003 was estimated at 2.03 million Mg while consumption was 3.96 million Mg. The balance of 1.90 million Mg was obtained by importation (FAO, 2004). Therefore, more effective use of IVs for rice cultivation offers the greatest potential of closing the gap between production and consumption. The objectives of this study were to: (i) investigate the growth and yield performance of upland rice fitted in-between lowland rice and dry season crops, and (ii) ascertain the possibility of growing three crops without reducing the yield of the main crops.

	MATERIALS AND METHODS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSION REFERENCES

 
The experiments were conducted in 3 yr (2000–2001, 2001–2002, and 2002–2003 cropping seasons) at the bottom of the IV of the University of Agriculture, Alabata, Abeokuta (7°20' N, 3°23' E), Nigeria. Using procedures described by Burt (2004), the top 1 to 20 cm soil layer had pH (1:2, soil/water) of 6.64, 17.4 mg kg^–1 K measured using Flame photometry 45.50 g kg^–1 organic matter (Walkley–Black method), 2.40 g kg^–1 total N (Macro-Kjedahl method) and 16.09 mg kg^–1 Bray extractable P. The textural class of the soil was loamy soil (784 g kg^–1 sand, 164 g kg^–1 silt, and 52 g kg^–1 clay). The soil series of the experimental site was Ikire (Aiboni, 2001). This is equivalent of Aquic Ustifluvents according to Aiboni (2001).

The available long-term climatic data include rainfall and mean temperature. The average annual rainfall is 1148 mm and average daily temperature is 28°C for period of 21 yr. Rainfall data during the study are presented in Fig. 1 . At the first peak of the bimodal rainfall during the rainy season, water table was above the soil surface. This receded to the soil level in August and became flooded again at the second peak of rainfall in September of each year. The IV used in this study had not been cultivated in the previous 12 yr.

View larger version (24K): [in this window] [in a new window]   Fig. 1. Rainfall data in Abeokuta during the study period.

The agricultural calendar year, which began in May and ended in April of the following year constituted a cycle. This experiment was conducted in three agricultural calendar years of 2000–2001, 2001–2002, and 2002–2003 cycles. Each cycle consisted of eight sequences that ran concurrently with each other. The sequences included the following: (i) lowland rice–upland rice–fallow, (ii) lowland rice–upland rice–okra, (iii) lowland rice–upland rice–amaranth, (iv) lowland rice–upland rice–cowpea, (v) lowland rice–fallow–okra, (vi) lowland rice–fallow–amaranth, (vii) lowland rice–fallow–cowpea, and (viii) lowland rice–fallow–fallow. Each sequence commenced in May with the planting of lowland rice as the first and the main crop. This was harvested in September. Two early maturing, upland rice cultivars were planted in October and harvested in December in first to fourth sequences. Two vegetables (okra and amaranth) and cowpea were planted in January and harvested in March in the second to seventh sequences whereas the first and eighth sequences was left fallow. Vegetables were chosen because they were the valuable crops grown with residual moisture without irrigation during the dry season to generate income. Each sequence was replicated three times on the same site. Table 1 shows a replicate of the various sequences used in the study.

The partially decomposed upland rice straw that was used for mulching in cowpea–vegetables crop was incorporated during land preparation for lowland rice whereas the residues of the preceding vegetables–cowpea were used for mulching in lowland rice plots. The basal fertilizer was applied at the rates of 30 kg N ha^–1, 7 kg P ha^–1, and 13 kg K ha^–1 in the form of N–P–K (20–10–10) at 14 d after planting (DAP) while the top dressing was 30 kg N ha^–1 in the form of urea for all treatments at 70 DAP.

A 1-m wide water channel was made within one of the walkways along the three replicates down the slope so as to enhance free flow of water. This dug trench turned out to become a small running stream during the rainy season of the remaining 2 yr of the experiments.

Cultivation of Upland Rice
The seeds of upland rice were sown on 28, 5, and 10 October in 2000, 2001, and 2002, respectively. The two varieties of upland rice were sown without bed construction in 2000–2001 cropping cycle. However, arising from the problem of poor stand establishment of upland rice as a result of wetness of the soil, raised beds were constructed in 2001–2002 and 2002–2003 cropping cycles to increase the depth of the water table. The upland rice was spaced 20 by 20 cm on 4-m row plot giving a total stand population of 250 000 plant stands per hectare. The 1st and 16th rows were considered as the border rows while the 2nd, 3rd, 14th and 15th rows were considered as sample rows. The net plot was made up of the 4th to 13th rows. The targeted plant population per hectare was 250 000, but the 3 yr avg. of the actual plant stands per hectare was 82 500 because of poor stand establishment arising from wetness of the soil.

Lowland rice straws in lowland rice–upland rice–fallow, lowland rice–upland rice–okra, lowland rice–upland rice–amaranth, and lowland rice–upland rice–cowpea sequences were always removed because of the difficulty in handling bulky lowland rice straw during the construction of bed for upland rice and the fact that there was little or no decomposition in flooded soil (Linn and Doran, 1984). The basal fertilizer was applied at the rates of 30 kg N ha^–1, 7 kg P ha^–1, 13 kg K ha^–1 in the form of N–P–K (20–10–10) at 14 DAP while the top dressing was 30 kg N ha^–1 in the form of urea for all treatments 60 at DAP.

Cultivation of Vegetables/Cowpea
The crops grown during the dry season were okra variety NHAe-47-4, amaranth, and cowpea variety IT90K-76. These crops were established on the residual soil moisture at the spacing of 80 by 20 cm for cowpea and 80 by 50 cm for okra while amaranth was drilled in at 40 cm between rows. A total of 1.28 kg of amaranth seed thoroughly mixed with 10 L of fine soil was used. This mixture of seed and fine soil was placed into the shallow opening of the soil and a wooden mallet was used to compress the drilled seed to enhance good contact between the soil and the seed. The crops grown during the dry season in the first cycle were sown on 9 Feb. 2001 whereas those of second and third cycles were sown 7 and 10 Jan. 2002 and 2003 on the flat, respectively.

The rice straws of the preceding upland plant and weed in the fallow plots were used as mulching during the vegetable/cowpea. No fertilizer was applied to cowpea. The basal fertilizer was applied at the rates of 60 kg N ha^–1, 13 kg P ha^–1, 25 kg K ha^–1 in the form of N–P–K (20–10–10) 20 DAP as a single dose for vegetables.

Data Collection
Three plant samples were taken from the sample rows of each plot for biomass at 45 DAP, 50% heading and at maturity. These samples were oven-dried to constant weight at 70°C. Other observations included the following:

Plant height was measured at maturity with the aid of graduated ruler from ground level to the tip of the panicle.

Grain yield of rice was determined from the 10 center rows that constituted the net plot (8 m², i.e., the 4th to 13th row of the plot). The brown panicles were harvested with the aid of a harvesting knife. The harvested panicles were sun dried, threshed, weighed, and converted to kilograms per hectare.

Soil Samples
Composite soil samples were taken from the entire experimental site before the commencement of the experiment for the determination of pH, organic C, N, P, and K. Another set of soil samples was taken from the sub-sub plots in September before upland rice cultivation of the second and third cycles of the experiment. These samples were analyzed to determine the effects of preceding crops on pH, organic C, N, P, and K between each cropping cycle. The moisture content was monitored weekly at 20-cm depth throughout the growth period of upland rice (i.e., from October to December) using gravimetric water content method. Gravimetric soil moisture content thus obtained was converted to volumetric soil moisture (Klute, 1986).

When water is applied to the soil by irrigation or rainfall, the quantity applied is reported as the depth of water if it were accumulated in a layer. Therefore, to report quantity of water so obtained in depth, the depth at which soil was taken on the field was multiplied by the volumetric water content. The groundwater table was also measured by using piezometer.

Open pan evaporation data were collected from the meteorological station. The weekly total of the evaporation data was compared with the weekly rainfall depth equivalent.

Cost and Returns Analysis
The labor rate/manday as well as the price/kilogram of milled rice were obtained from Ogun State agricultural Development Program (OGADEP), Ogun State, Nigeria. For the cost and return analysis determination, paddy rice was converted to milled rice by multiplying the yield ha^–1 and 0.76 (76% of paddy rice is made of milled rice) (FAO, 2003). The obtained value was multiplied by the milled rice price as at the time it was harvested. The costs and return analysis for rice includes cost of the following inputs: land preparation, seed, seeding, weeding, fertilizer, fertilizing, and harvesting. It does not include parboiling, milling, and management because their labor rates/manday were not available. Cost of input for vegetables were land preparation, seed, seeding, weeding, fertilizer, fertilizing, and harvesting; while those of cowpea included land preparation, seed, seeding, weeding, insecticide, spraying of insecticide, harvesting, threshing, and winnowing.

The data generated from the lowland rice and upland rice was subjected to analysis of variance using split-split plot design. The soil chemical properties from the soil samples taken before upland rice in each sub-sub plot were also subjected to analysis of variance. MSTAT-C program version 2.00 (Freed, 1988) was used to run these analyses. Duncan Multiple Range Test (DMRT) was used to separate the treatment means.

	RESULTS AND DISCUSSION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSION REFERENCES

 
The pooled grain yield and growth parameters of the preceding lowland rice in all the three cropping cycles were similar (Table 2). However, the preceding lowland rice variety FAROX 317-1-1-1 had significantly higher plant height and grain yield than that of BW 311-9. Okeleye et al. (2002) who evaluated several lowland rice varieties for grain yield performance reported similar results. Biomass at tiller of lowland rice in lowland rice–fallow–fallow sequence was higher than those of the other sequences whereas the biomass at harvesting of lowland rice in lowland rice–upland rice–fallow and lowland rice–fallow–fallow sequences were higher than those of the other sequences. This difference could be attributed to the inclusion of fallow in the two-crop and one-crop sequences. Consequently, the microbial decomposition of the preceding crops during the dry season fallow period of one-crop and two-crop sequence could enhance the growth of lowland rice. Grain yield of lowland rice in the various sequences with or without upland rice were similar. This suggests that the inclusion of upland rice in the sequence did not affect the performance of the lowland rice (main crop). Hence, the niche could be used to grow upland rice without yield reduction of the other crops in the sequence. The interactions of cropping cycle x lowland rice variety on plant height and cropping cycle x crop sequence on biomass at harvest were significant. This suggests that the plant height of the two lowland rice varieties and biomass at harvest of the cropping sequences responded differently in the cropping cycles. The plants height and biomass at harvest in the 2000–2001 cropping cycle were significantly higher than those of 2001–2002 and 2002–2003 cropping cycles. This is an indication that the performance of lowland rice was declining.

The grain yields of the two upland rice varieties were similar in lowland rice–upland rice–vegetable/cowpea sequence (Tables 3). However, ITA 150 had significantly higher plant height than ITA 257. These results agree with the finding of Adigbo et al. (2003). The yield obtained in an upland ecology was substantially higher than that of inland valley. This is contrary to yield expectation from IVs that are generally believed to have more fertile soils and more available water than the adjacent uplands (IITA, 1990). The low grain yield in IV as compared to upland ecology could not be attributed to the soil nutrients alone but also to poor stand establishment as a result of wet soil at the time of planting. The mean levels of N, P and K available to upland rice after harvesting of lowland rice were above the critical level in the rating of soil fertility classes by Enwezor et al. (2002). With the additional fertilizer applied (60 N kg ha^–1) in two doses at 14 and 60 DAP, high grain yield would have been expected. It is therefore, apparent that low yield of upland rice in the IV was more of poor stand establishment due to the saturated soil. This poor stand establishment in 2000–2001 led to the idea of raised bed. But the raised bed did not improve the stand establishment in 2001–2002 and 2002–2003 cropping cycles.

There was a general decrease in soil fertility status between cropping cycles (Table 4). The general decrease in grain yield of upland rice in 2001–2002 and 2002–2003 compared to 2000–2001 was a true reflection of the general decline in soil fertility status. Beside, the preceding lowland rice residues were always removed during bed forming because of its bulkiness and anaerobic condition of the soil that limit decomposition (Linn and Doran, 1984). Thus, the nutrients immobilized within the straw of the lowland rice were not available to the succeeding upland rice. These facts explained in part the low yield obtained from the three crops of upland rice in the three cropping cycles as compared to the obtainable yield of 1.5 Mg in the upland ecology (IITA, 1990).

The soil moisture contents at 20-cm depth expressed as rainfall depth equivalent during the growth period of upland rice ranged from 60.8 to 77.7 mm (Fig. 2 ). The evaporative demand of upland rice was consistently lower than the rainfall depth equivalent in the three cropping cycles. This suggests that the short niche has sufficient moisture to support second rice. However, the saturated state of the soil during the planting of upland rice accounted for the poor crop establishment. It is pertinent to note that the few rice plants that germinated in the wet soil actually thrived well. This is an indication that, if the problem of poor establishment in the niche is improved, higher yield could be obtained.

View larger version (44K): [in this window] [in a new window]   Fig. 2. Comparison of evaporation and rainfall depth equivalent during the growth of upland rice.

The inclusion of upland rice in the sequence had no effect on the benefit/cost ratio of the lowland rice (Table 5). The net revenue of upland rice in the triple cropping was

View this table: [in this window] [in a new window]   Table 5. Mean grain yield of cropping sequence in the three cropping cycles and economic analysis of cropping sequence.

	CONCLUSION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSION REFERENCES

 
Based on this study, it is obvious that farmers could grow additional upland rice crop in-between lowland rice and vegetable/cowpea sequences without reducing the yields of lowland and vegetable. However, the inclusion of upland rice in the sequence has led to decrease in the overall benefit/cost ratio of triple cropping rather than increasing it. Thus, two-crop sequence, which is currently being practiced by the traditional farmers, should be adhered to. Further research is necessary to develop appropriate crop establishment of upland rice in lowland ecology.

	REFERENCES

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSION REFERENCES

 

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This Article Abstract Figures Only Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Adigbo, S. O. Articles by Adigbo, V. B. Search for Related Content PubMed Articles by Adigbo, S. O. Articles by Adigbo, V. B. Agricola Articles by Adigbo, S. O. Articles by Adigbo, V. B. Related Collections Crop Rotation Systems Rice Crop Systems