(227 cm) of 1 st ra toon sugarcane in 'pineapple' planting arrangement (227 cm and 97 cm) under irrigated conditions. Up to 0.

Transcription

1 NTERCROPPNG OF FRST RATOON SUGARCANE WTH RCE N MAURTUS A. R. Pillay Mauritius Sugar ndustry Research nstitute, Reduit ABSTRACT A study was undertaken to investigate the possibility of intercropping ratoon sugarcane with rice. When intercropped as upland rice in inter-rows of sugarcane planted at the conventional row spacing of 1.50 m, rice varieties used in flooded paddies of Mauritius showed very low yields. ntercropped rice had no significant adverse effects on the sugar yields. Yields up to 1.6 tons/ha were obtained with shortcycle rice varieties planted in every second inter-row (227 cm) of 1 st ra toon sugarcane in 'pineapple' planting arrangement (227 cm and 97 cm) under irrigated conditions. Up to 0.9 tons of rice per ha were obtained under rainfed conditions. NTRODUCTON ntercropping of May-June planted sugarcane has been well-adopted by small and big planters in Mauritius. Among the crops, beans, peas, and potatoes have been recommended for intercropping on the basis of soil suitability and abailability, of irrigation facilities. As a result however, of the increasing demand for other food crops and the limited cultivated land, the need to exploit the cultivable inter-rows of ratoon sugarcane arose. Thus, groundnut, maize, and soybean are now being planted in inter-rows of the first and second ratoons. Recently, it had become necessary to study the possibility of intercropping sugarcane with rice. /Mauritius consumes some 60,000 tons of processed rice annually, representing an expenditure of Rs 100 m. t is therefore important to increase rice production, which now is a mere 400 tons annually from flooded paddy fields. Because of the uneven topography of the island and the rocky nature of the soils, conventional rice cultivation by flooding would demand very excessive investments and high water consumption. t appears that rainfed or overhead irrigated upland rice cultivation may offer more attractive prospects on any atterrlpt to increase rice production on a large scale. This paper deals with a study of intercropping sugarcane ratoons with upland rice under irrigated and rainfed conditions. The effect of competition

2 between rice and the main cropqwas determined when rice was intercropped in sugarcane planted at the conventional spacing of 1.5 m between rows. On account of shortage and high cost of labor, mechanization of harvesting and planting of cane has recently been tried in Mauritius. This resulted in changes particularly in the traditional row spacing. Such changes which included planting sugarcane alternately in rows 227 cm and 97 cm apart, were found to have no adverse effect on cane and sugar yields. The wider rows, at the same time, provided an attractive possibility for intercropping rice. Competition between the two crops is less when the wider rows are used. Experiment MATERALS AND METHODS n the first experiment, a randomized block design with 6 replicates was used, with three rice varieties, direct-seeded as intercrops in first ratoons of sugarcane S 17 at Fuel, and M at Belle Vue Haral. Two additional treatments, cane grown alone and transplanted TN rice seedlings as intercrop, were also included. The empirical plot consisted of 4 rows of sugarcane 8 m long and spaced at 1.50 m. Four rows of rice were planted in every second cane inter-row. nter-row spacing of the intercropped rice was 20 cm. Plots were irrigated at a rate of 18 mm every 3 days. The plots were harvested when the various rice varieties reached maturity and when the sugar cane reached the 12th month. Data on rice grain and sugar yields at FUEL were subjected to an analysis of variance. Significance of analysis results was based on the 5% level of probability. Experiment 1 Three rice varieties in the second experiment were intercropped in first ratoon crop of sugarcane under irrigated and rainfed conditions. The trials were conducted in two sites on two dates under the conditions listed in Table 1. RESULTS AND DSCUSSON n Mauritius, the sugarcane crop is usuallv grown at a spacing of 1.5 m between the rows. The cane is grown in furrows and the leaves of the cane do not shade the inter-rows until 4 to 5 months after planting. With the first ratoons, under conditions of high temperatures and adequate moisture, as were the case in the present experiment, shading of inter-rows occurred earlier, that is, 3% to 4 months after cropping. Yields of rice variety TN (the commercially grown rice variety) at Fuel (Table 2) was very low. A very high percentage of the seeds were due to the shading of cane interrows during grain filling period of rice (Fig. 1). The more rapid and vigorous growth of the cane variety M at Belle Vue Harel, severely affected grain filling of the rice varieties. The results showed that the rice varieties had too long a growth cycle and were not suitable as intercrops. However, it was found that

3 A. R. P LLAY 25 the rice varieteis planted in every second cane inter-row, had no significant adverse effects on sugarcane and sugar yields, as shown in Table 3. TABLE 1. Experimental conditions at Fuel and Benares Condition Fuel Benares Altitude 125 m 100 m Rows rrigation Soil type Soil ph Cane variety Low Humic Latosol Low Humic Latosol S 17 (1st ratoon) S 17 (1st ratoon) Spacing between cane rows Alternately 227 cm and 97 cm Alternate1 y 227 cm and 97 cm of rice planted 4 rows, 9 m long and 4 rows, 9 m long and in every 227 cm 20 cm apart 20 cm apart cane inter-row Overhead, 18 mm/3 days None Planting dates First Second 9 September, December, October, December, 1976 TABLE 2. Grain yield and other characteristics of rice in inter-raws of sugarcane ratoons - Fuel and Belle Vue Harel Variety Yield* (kglha) Days to 50% flowering Fuel Belle Vue Fuel Belle Vue R 532 E YRL TN TNl (transplanted) ** ANOVA LSD cv % 20

4 26 AGRONOMY TABLE 3. Cane and sugar yields. at Fuel Treatments Sugarcane yield (tonslha) mr.s.c, Sugar yield (tonslha) Control R 532 E YRL TN TN (transplanted) ANOVA n.s. n.s. n.s. CV % FGURE 1. Shading of rice before maturity in inter-rows of sugarcane spaced at 1.5m

5

6 28. AGRONOMY Results of the second experiment (Table 4) showed that Kwang Loo and Red Plum Zao had short growing cycles and matured well before the cane canopy had covered the inter-rows (Fig. 2). Kwang Loo yielded slightly less than Red Plum. Chan Chui No. 11, a potentially high yielder, had a comparatively longer growing cycle and did not reach maturity before being over shadowed by the cane canopy. A comparison of rice yields obtained under the two moisture conditions clearly showed, as expected, inferior yields in grain under rainfed condition. That was probably due to an irregular rain distribution during the growing season. The rice plants sometimes exhibited stress symptoms. Red Plum and Kwang Loo showed promise for cane inter-row cultivation under both irrigated and rainfed conditions. TABLE 4. Grain yield and other characteristics of rice varieties in inter-rows of sugarcane ratoons - Fuel and Benares Variety Yield (tlha)" Days Plant height (cm) flowering Trial Trial 2 Trial Trial 2 Trial Trial 2 Fuel (irrigated) Kwang Loo Red Plum Zao "" Chen Chui No "* Benares (rainfed) Kwang Loo Red Plum Zao No 'At 1296 moisture content Twenty-six percent of the sugarcane field was used for rice cultivation. "" Sevedy damaged by birds CONCLUSONS 1. The rapid growth of ratoon canes with the conventional row spacing of 1.5 m in Matlritlus, limits the period that may be used by a rice crop in the inter-rows, to approximately 105 to 1 10 days. 2. Rice variety TN, commercially used in paddy fields, is too late maturing for upland cultivation in sugarcane inter-rows. 3. The wider cane interrows (227 cm) are well suited for a rice crop. Shortcycle varieties, such as Red Plum and Kwang Loo, are suitable as intercrops with yields up to 1.6 tonslha under irrigated conditions.

7 4. Rice yields under rainfed conditions are inferior to yields under irrigated conditions. NTERCALADO DE UN PRMER PETORO DE CARA DE AZUCAR CON ARROZ EN MAURCO A. R, Pillay RESUMEN # Se emprendio un estudio para investigar la posibilidad de intercalar caiia de azucar en retoiio con arroz. Se obtuviersn rend.& mientos rnuy bajos con las variedades de arroz utilizadas en campos inundados en Mauricio, cuando se intercalo como arroz en secano entre las hileras de cafia de azucar sembrada a1 espaciamiento convencional entre hileras de 1.50 m. El arroz intercalado no afecto adversamente de manera significativa 10s rendimientos de azucar. Se obtuvieron rendimientos de hasta 1.6 ton/ha con variedades de arroz de ciclo corto sembrado cada segunda hilera (227 cm) de caiia de primer retoiio en niembra tipo "pifia" (227 cm y 97 cm) bajo riego y hasta 0.9 ton/ha en secano.