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African Crop Science Journal
African Crop Science Society
ISSN: 1021-9730 EISSN: 2072-6589
Vol. 9, Num. 3, 2001, pp. 567-575

African Crop Science Journal, Vol. 9. No. 3, pp. 567-575



Department of Research and Specialists Service, Agronomy Institute, P. O. Box CY 550,
Causeway, Harare, Zimbabwe

Received 27 July, 1998
Accepted 22 March, 2001

Code Number: cs01075


A two-season (1992/93 and 1993/94) field study was conducted to compare the economic returns of castor (cvs 'Hale', Guarani', 'H22' and 'Aruna') with sunflower (cv 'Mopane) and a white-seeded sorghum (cv 'SV 2'), in some semi-arid environments of Zimbabwe. Castor is currently undergoing a strong promotion drive for production, while sorghum and sunflower are already established in the cropping systems of the smallholder farmers in these environments. Trial fields were on medium-grained granitic sands (~ 8% clay and >85% sand) in Natural Regions (NR) III (Mlezu), with a mean annual rainfall of about 700 mm and IV (Makoholi and Matopos, with a mean annual rainfall of 650 and 572 mm, respectively). From seed yield data pooled over the two seasons, returns per dollar invested in producing a crop ($3.53, $5.04 and $6.82 for castor; $3.22, $1.66 and $1.72 for sunflower and $0.68, -$0.59 and -$0.78 for sorghum at Matopos, Makoholi and Mlezu, respectively) were calculated using the 1994/95 producer prices of $2150, $1500 and $750 t-1 for castor, sunflower and sorghum, respectively. A break-even analysis also showed that a farmer expecting a minimum rate of return of 75% above the total costs that vary, would still find it profitable to grow castor even at 50% yield reduction, with the lowest yield attained (356 kg-1). Despite a 57% lower net gain from sunflower compared to castor production, production of the former was also profitable in these environments. Results from the study suggest that growing white-seeded sorghum cv 'SV 2' was unprofitable. Implicitly, the latter might only be acceptable as food security crop at the household level rather than a cash crop, even under semi-arid conditions, as long as yields and the formal market price paid to the farmer remained very low. The results also indicated that castor production was more favourable in NR III than in IV.

Key Words: Break-even price, gross benefit, minimum acceptable rate of return, net benefit, total costs that vary


Une étude en champs de deux saisons (1992/93 et 1993/94) a été conduite pour comparer des revenus économiques de 4 cultivars de castors (Hale , Guarani, H22, et Aruna) avec le cultivar de tournesol, Mopane et un cultivar de sorho à graines blanches, SV2, dans quelques environnements semi-arides du Zimbabwe. Actuellement, le costor est entrain de traverser une période d'importante promotion de production, alors que le sorgho et le tournesol sont déjà établis dans ces environnements. Des essais en champs étaient établis sur des sables à graines moyennes granitiques (~8% argile et >85% de sable) dans les Régions Naturelles (RN) III (Mlezu), avec une précipitation moyenne annuelle d'à peu près 700 mm et IV (Makoholi et Matopos), avec des précipitations moyennes de 650 mm et 572 mm respectivement. A partir des données des rendements des graines combinées pour deux saisons, des revenus par dollar investi dans la production de la culture ($3.53, $5.04 et $6.82 pour castor; $3.22, $1.66 et $1.72 pour le tournesol et $0.68, $0.59 et $0.78 pour le sorgho à Matopos, Makoholi et Mlezu, respectivement) ont été calculés sur base des prix d'un producteur de 1994/95 de $2150, $1500 et $750 t-1 pour le castor, le tournesol et le sorgho, respectivement. Une analyse partielle a montré aussi qu' un agriculteur expectant un taux minimum de revenu de 75% au dessus des coûts totaux qui varient, trouverait encore profitable cultiver le castor même à une réduction de 50% du rendement, avec le rendement le plus bas obtenu (356 kg). Malgré le plus bas bénéfice net du tournesol de 57% comparativement au castor, le dernier était aussi profitable à cultiver dans ces environnements. Des résults de cette étude suggèrent que cultiver un cultivar de sorgho à graines blanches, SV n'était pas profitable. Conséquement le dernier pourrait être acceptable comme une culture de sécurité alimentaire plutôt qu' une culture de rente, même dans les conditions semi-arides, bien que les rendements et le prix du marché informel payé au fermier restent très faibles. Les résultats ont montré aussi que la production du castor était plus profitable dans la RN III que dans RN IV.

Mots Clés: Prix partiel, bénéfice total, prix minimum acceptable, taux de revenu minimum acceptable, bénéfice net, coûts tataux qui varient


Sunflower (Helianthus annuus L.) and sorghum (Sorghum bicolor (L.) Moench) are reported to have drought evading characteristics during certain phenological stages of their growth. As a result, they are well established in the cropping systems and are widely grown by smallholder farmers in many semi-arid areas of Zimbabwe, particularly in Natural Regions (NRs) III, IV and V, with annual long-term mean rainfall of 650-800, 450-650 and below 450 mm, respectively (Vincent and Thomas, 1961). Castor (Ricinus communis L.) on the other hand, is a crop that has been undergoing a promotion drive for production in similar environments of Zimbabwe since the mid 1980s.

Most of the sunflower produced in Zimbabwe is used for oil extraction and it ranks third after cotton seed and soybean in the edible oil seed industry. Production of the crop in Zimbabwe is dominated by smallholder growers who produce over 90 percent of the national crop (Commercial Agriculture in Zimbabwe, 1986, 1991; AMA, 1989, 1992). Between 1983/84 and 1994/95 season, sunflower was a 'controlled commodity', meaning that its disposal on the formal market was controlled by the Grain Marketing Board (GMB), with prices paid to the producer determined by a process of negotiation between the farmer organisations, the GMB and the Ministry of Agriculture. Since the commodity 'de-control' in 1994/95 season, the GMB acts as a residual buyer with a 1994/95 producer price of Z$1500 per metric tonne of clean seed.

Sorghum is the third most widely grown summer cereal in Zimbabwe after maize and pearl millet. It is estimated that over 200,000 ha are grown annually by communal area farmers who now account for about 98% of the crop (CSO, 1970-1993). Like sunflower, disposal of sorghum on the formal market was also controlled by the GMB until the 1994/95 season. However, the GMB now acts as a residual buyer and offers a price of Z$750 per metric ton of grain.

Weiss (1983) reported that although there were strong indications that castor originated from the eastern Africa sub-continent, it has spread to many parts of the world and established itself as a 'native' plant. In Zimbabwe, it can be seen growing in the wild and particularly around cattle kraals (pens) where there is manure. Uses of castor oil and its derivatives are wide ranging and include production of sebasic and undecyclenic acids used in manufacturing plasticisers and nylon. Some of the uses include production of greases and lubricants for jet engines, making ink and paint oils (Zimmerman et al., 1958). If properly treated, the cake, after oil expression, can be used as a fertiliser (Fundire, 1991). In Zimbabwe, most of the oil and its derivatives are used to prepare the trinepon range of products, vinyl floor tiles, paints, putty, antiseptics and disinfectants (Hikwa, 1989). Therefore, its strategic value to Zimbabwe as a country cannot be overlooked.

Following the re-introduction of an active castor research programme in 1982/83, the area under this crop has been increasing slowly, but steadily. The promotion drive for castor production has largely been done by two companies. One of these companies (Trinidad Industries) has been able to acquire and sell seed, as well as review its producer price annually to attract more growers. The current 1995 producer price offered by Trinidad Industries is Z$2150 per metric ton of clean seed.
The facts that castor is a crop being promoted for production in the smallholder sector of the semi-arid areas of Zimbabwe and also the fact that sunflower and sorghum are already established in these cropping systems,were taken into account in conducting this study. The crops were compared for their potential economic returns to the farmer, with the main aim of providing information that would enable the farmer to make informed decisions on choice and extent of production of any of the three crops.

The main objective of the study was to evaluate and compare the economic returns of castor with those of possible competitor cash crops (sunflower and sorghum) on smallholder farms in semi-arid areas (Natural Regions III and IV) of the country.


This comparative study was conducted over two seasons (1992/93 and 1993/94) at three research station locations in Natural Regions III (Mlezu) with a long-term annual mean rainfall of about 700 mm and IV (Matopos and Makoholi, with long-term annual mean rainfall of 572 and 650 mm, respectively) (Whingwiri et al., 1987). Fields used at all three locations were on medium grained sandy soils derived from granite, with about 8% clay and more than 85% sand (Chemistry and Soils Research Institute Guidelines, 1985).

Open pollinated castor cultivars 'Hale' (ex-USA), 'Guarabi' (ex-Brazil), 'Aruna' (ex-India mutant, which is not yet on the local market) and a hybrid 'H 22' (ex-Israel) were compared with sunflower hybrid 'Mopane' (ex-Crop Breeding Institute (CBI), DRSS) and a white-seeded open-pollinated sorghum cultivar 'SV 2' (ex-CBI, DRSS). Duration to maturity of the castor cultivars used is 100-120 days for 'H 22', 120-130 days for 'Hale' and 'Guarani', 140-150 days for 'Aruna', 110-115 days for the sunflower cv 'Mopane' and 115-125 days for the sorghum cv 'SV 2'. Sunflower rows were spaced at 90 cm apart with 30 cm between plants in the row, giving a plant density of 37000 plants ha-1. Sorghum was sown in rows 75 cm apart with an in-row spacing of 13 cm between plants, resulting in a plant density of 100,000 plants ha-1. Castor cultivars were spaced according to their growth habits. Cultivars 'Hale and 'Aruna' were in rows 90 cm apart with 50 cm between plants in the row. Row spacing for 'Guarani' and 'H22' was 100 cm, with in-row spacings of 100 cm and 150 cm, respectively. Gross plots were 45 m2 for 'Hale', 'Aruna' and 'Mopame'. Those of Guarani, 'H22' and 'SV 2' were 24 m2. The trial was laid out in a randomised complete block design with four replicates.

Compound 'L' (5% N; 18% P205; 10 K2O; 8% S; 25% B) was used as a basal dressing on sunflower at a rate of 250 kg ha-1. Ammonium nitrate (34.5% N) was later applied at six weeks after planting at a rate of 45 kg ha-1. Sorghum and castor both received 250 kg ha-1 compound 'D' (8% N; 14% P2O5; 7 K2O; 6.5% S) at planting. Ammonium nitrate at a rate of 30 kg ha-1 was later applied to sorghum at boot stage and to castor at primary flower initiation.

Several steps were followed in calculating economic returns from the three crops, using partial budgets. Data from each crop were pooled over the two seasons (1992/93 and 1993/94) and subjected to analysis of variance to estimate seed yields per hectare. The estimated yields (kg ha-1) were then adjusted downwards by 5% for castor and 10% for sunflower and sorghum. Since the study was done on stations these adjustments were estimated to be the amount of yield loss that could occur under farm management. A higher coefficient of adjustment was used for sunflower and sorghum because of their proneness to bird damage. Gross benefits were derived by using the formula GB = FP X Yadj, where GB - gross benefit, FP = farm price and Yadj. = adjusted yield. The farm price was derived by subtracting cost of transporting produce to the market and cost of labour for harvesting and shelling from the producer price of a crop. The 1994/95 producer prices were $1500, $750 and $2150 per metric ton for sunflower, sorghum and castor, respectively. To estimate net benefits ($ ha-1), total costs that vary (TCV) were substrated from the GB, i.e., GB-TCV = NB, where NB = net benefit. TCV included cost of seed and labour for planting and weeding in each crop and additionally, for bird scaring in sunflower and sorghum. Returns per dollar invested were based on the formula NB/TCV.

In addition to calaculating net benefits and returns per dollar invested, a break-even analysis was done on yield adjusted by various percentages (50, 30 and 20), with a minimum acceptable (to the farmer) rate of return of 75% above TCV. The assumption was that if a farmer were to consider growing any of the three crops in the semi-arid environments of NRs III and IV, he/she would find it attractive if the rate of return was 75% or more than what was invested in producing the crops. At each yield adjusted level, a break-even price ($ kg-1) was calculated. The minimum acceptable price (MAP) would ensure that in addition to covering TCV, a farmer would also make a profit of 75% in this case.

Cost of seed was based on 1994/95 retail prices ($15.00 for open pollinated castor cvs 'Guarani', 'Aruna' and 'Hale'; $35.00 for hybrid cv 'H22'; $3.20 for sorghum cv 'SV 2' and $17.00 kg-1 for sunflower cv 'Mopane'), to which transport costs from point of purchase to the farm were added. Transport costs were based on 1994/95 rates of $0.10 kg-1 of seed (Diyo Transport, Masvingo). Labour was valued at $9.60 per 8 hour day. Sowing dates for the crops are shown in Table 1.


The 1992/93 season was wetter than the 1993/94 season and the NR IV sites received more rainfall than the NR III site. In both seasons, there was variation in both timing and length of dry spells at all sites.

Pooled results of the two seasons (1992/93 and 1993/94) show that castor cultivars 'Aruna' and 'Guarani' produced similar yields at Matopos. However, due to the differences in variables costs (attributable to differences in amounts of seed used according to spacing of each cultivar), 'Guarani' gave a higher net return per dollar invested than 'Aruna', while 'Hale' was the least remunerative of the four cultivars at this site (Table 2). At Makoholi, 'H22' had the highest yields and net returns per dollar invested. Yields and returns of 'Hale' were again inferior to the rest of the cultivars at this site. At Mlezu, 'Aruna' gave the highest yields, whereas 'Guarani' gave the least. The best economic returns were realised from growing 'H22', while again 'Hale' was the least profitable at this latter site (Table 2).

Grain yields of sorghum were highest at Matopos and lowest at Mlezu (Table 3). The low yields at Makholi and Mlezu were attributed to stunted growth and die-back, particularly in the first season. The resultant net returns of sorghum at the two sites were negative (Table 3).

Best yields of sunflower were achieved at Matopos (Table 3). It is also at this site where the largest sunflower heads were observed. This is supported by work done in other studies in which positive correlations between head size and seed yield were established (Alessi et al., 1977; Hikwa and Kangai, 1992). Sunflower yields at Makoholi and Mlezu were comparable and so were the net returns.

Castor had higher yields than sorghum and sunflower at Makoholi and Mlezu, and this resulted in higher net returns of castor compared to the other crops (Table 3). However, sorghum had very good yields at Matopos, but because of the lower formal market price of $750 t-1 compared to $2150 and $1500 t-1 for castor and sunflower, respectively, the crop was not profitable. However, when the informal market price ($2000 t-1) of sorghum was considered, the crop at Matopos realised a net gain of $4.26 per dollar invested as opposed to the negative return of $0.32 observed when the formal price was used to calculate returns (Table 4).

The break-even price (BEP) for castor cultivars at Matopos ranged between $0.29 and $0.90 kg-1. Correspondingly, the MAP also ranged between $0.51 and $1.58 kg-1 (Table 5). Castor cv 'Guarani' had the lowest BEP, while 'Hale' had the highest at all three levels of yield adjustment at this site. The BEPs were not very different when yields were reduced by 20% or 30%. However, a yield reduction of 50% resulted in a substantial increase in BEP and correspondingly, an increase in the price that would be acceptable to the farmer (Table 5). Compared to castor, sorghum and sunflower on average required lower BEPs and hence lower MAPs to satisfy the 75% acceptable rate of return at yield reductions of 20 and 30% at the Matopos site.

At Makoholi, the MAP for castor ranged between $0.33 and 1.60 kg-1, with cv 'H 22' having the lowest BEPs and 'Hale' the highest again. Due to very low yields of sorghum, very high prices were required to break even at all yield adjustment levels (Table 6).

The BEPs for castor were lowest at Mlezu where 'Hale', which had the highest BEPs, had values ranging from $0.31 to $0.49 kg-1 (Table 7). The BEPs required for sorghum were four times those of castor and sunflower at the latter site.


Due to their high plant population of 22 222 plants per ha, field establishment of castor cultivars 'Hale' and 'Aruna', required double the amount of seed per ha than for 'H22' and 'Guarani'. The two cultivars also required more labour hours for planting, thinning and weeding because of close spacings. As a result, their variable costs were double those of 'H 22' and 'Guarani'. Despite similar variable costs between cultivars 'Hale' and 'Aruna', better net returns per dollar invested were achieved with 'Aruna' because of better yield performance than 'Hale'. Given the small margins in returns per dollar invested in producing hybrid 'H 22' compared to the open pollinated cvs 'Guarani' and 'Aruna', it may be logical (for now) that farmers settle for production of open pollinated cvs with a similar performance to the latter two, since their seed cost per kilogramme is $20.00 less than that of hybrid 'H 22'. Overall, castor production was more profitable at the NR III site (Mlezu) than at the NR IV sites (Makoholi and Matopos), as reflected by the yields as well as the returns per dollar invested.

Across cultivars and sites, the net returns from growing castor were 57.1% more than those of sunflower cultivar 'Mopane'. If at the lowest yielding site (Makoholi) yields of sunflower cultivar 'Mopane' were to be reduced by 50%, the MAP of $1.22 kg-1 based on 75% acceptable rate of return above the TCV was $0.28 less than the $1.50 kg-1 offered by the GMB. Therefore, the growing of sunflower cultivar 'Mopane' in these environments was still profitable despite the percentage reduction in net gain when compared to castor.

The study also seems to suggest that growing of the white-grain sorghum cultivar 'SV 2' was unprofitable as long as the formal market price of $2.00 kg-1 was maintained; profitability from growing the cultivar seems to be only possible with yield levels well above 500 kg ha-1, as demonstrated by the good net gains at Matopos. By comparison, yield levels attained at Makoholi and Mlezu were such that even if the informal price were to be paid it would still not be profitable to grow the crop.


The main conclusion that can be drawn from this comparative study is that of the three crops evaluated using the current yield levels and producer prices offered on the formal market, castor production is the most profitable, followed by sunflower in the sandy soils of the semi-arid environments. Unless much higher yields than those attained at Makoholi and Mlezu are achieved, production of the white-seeded sorghum cultivar 'SV 2' may be shunned by farmers and if at all it is produced, it may be primarily for food security at the household level rather than a cash crop, even in these harsh environments.


The authors would like to acknowledge the Agronomy Institute Crop Productivity Unit Teams at Makoholi Experiment Station, Cotton Research Institute (Kadoma and Mlezu) and Matopos Research Station under the leadership of H.H. Dhliwayo, M. Chisenga and C. Ndebele, respectively, who meticulously collected data in this study. Our thanks also go to M. Mudhara for his valued comments on the economic analysis, and to B. Nhamburo for assisting in logging the raw data into the computer.

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© Copyright 2001, African Crop Science Society

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