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Multiple benefits

Sweet sorghum ( Sorghum bicolor ) is similar to grain sorghum with a sugar-rich stalk, almost similar to sugarcane. Besides having wide adaptability, rapid growth and high sugar accumulation and biomass production potential, sweet sorghum, is tolerant to drought, water logging, soil salinity and acidity toxicity. It has great potential for jaggery, syrup and alcohol (most importantly Gasohol, which is ethanol blended with petrol) production. The sugar content in the juice extracted from sweet sorghum varies from 16-23% Brix.

In recent years, there is increased interest in the utilization of sweet sorghum for ethanol production in India as its growing period of about four months, and water requirement of 8,000 cubic meters (cu m) over two crops are one-fourth that of sugarcane, which has a growing period of 12 to 16 months and a water requirement of 36,000 cu m per crop. In addition, sweet sorghum is better suited for mechanized crop production and seed propagation.

According to a pilot study conducted by VSI, sweet sorghum is the best alternative raw material, which can supplement the use of sugarcane in ethanol production. At 5,600 liters per hectare per year (over two crops, at 70 tons per hectare of millable stalk per crop at 40 liters per ton), the ethanol production from sweet sorghum compares well with the 6,500 liters per ha per crop for sugarcane (at 85-90 tons per hectare of millable cane per crop at 75 liters per ton).

According to estimates made by National Research Center for Sorghum (NRCS), Hyderabad-India, the per liter cost of production of ethanol from sweet sorghum is Rs 13.11* (at Rs 500 per ton of stalk), when compared to Rs 12.55* (at Rs 1,600 per ton of stalk) from sugarcane molasses. However, the increased cost of production of ethanol from sweet sorghum is more than compensated by grain yield of 1 ton per hectare (which can be used as food or feed) and the superior quality of ethanol. The really significant advantage is that the production of ethanol from sweet sorghum is environment friendly since it uses the non-molasses route.

Further, the stillage from sweet sorghum after the extraction of juice has a higher biological value than the bagasse from sugarcane when used as fodder for animals, as it is rich in micronutrients and minerals. It could also be processed as a feed for ruminant animals. Apart from these, stillage contains similar levels of cellulose as sugarcane bagasse, therefore has a good prospect as a raw material for pulp product.

In India, the estimated requirement for ethanol to blend with petrol (at 10%) is about 1000 million liters, and for blending with diesel (at 5%) another 3000 million liters. Total ethanol requirement including other purposes is 5000 million liters. The possible ethanol production from available sugarcane molasses (8.2 million tones) and other sources is 2000 million liters. This leaves a gap of 3000 million liters of ethanol. The deficit of ethanol can be made good if sweet sorghum cultivation is promoted for ethanol production.

*1 Rs = 1.04 Php

Sweet sorghum like sugarcane is rich in sugar. But compared to sugarcane which takes 12-16 months to mature, sweet sorghum’s gestation period is only four months. Ethanol, a cheaper source of fuel, is the valuable product derived from processing sweet sorghum. Once ethanol is combined with diesel, it is converted as “gasohol.” Sweet sorghum can be used as animal feed after extracting ethanol.

Important Features of Sweet Sorghum

1. Seed crop matures in 100-110 days after emergence (DAE), the ratoon in 85-95 days after cutting. Sugarcane is harvested 300-330 DAP.
2. Because it is early maturing, it can be planted as a component crop in a multi-cropping system. It can be planted after rainfed lowland rice, upland rice, corn or legumes.
3. Drought tolerant. ICRISAT data has shown that sweet sorghum needs about 4,000 m3 of water/crop while sugarcane needs more than 36,000 m3 per crop.
4. Since sweet sorghum is drougt tolerant, it can be planted after rainfed lowland rice. It can be a good alternative crop for tobacco in areas where high quality leaves cannot be produced.
5. Higher yield per unit area per unit time.
   • sugarcane: 65-95 ton/ha.
   • sweet sorghum: 50-60 ton/ha in 100-110 DAE see crop; 45-65 ton/ha in 85-95 days after cutting (DAC) in ratoon crop (or 95-125 ton/ha from the same piece of land in 190-210 days compared to 65-95 ton/ha in 300-330 days in sugarcane). A second and third ratoon can be harvested with a stripped stalk average yield of 60 ton/ha.
6. Sugar content: 15-23%; normally higher during dry season.
7. Fertilizer requirement - 80-60-60 for clay soil; 100-60-100 for sandy loam.

Other Information on SPV422 Variety

• Stalks can be harvested within 10 days after harvest of grains but the brix content reading will be 14-18% and juice content will be 48-50% only.
• If harvested without grains or 20 days earlier (at physiological maturity), sugar content (brix) will be 16-23% and juice content will be 55-60%.

Production Technology

Site Selection

Good surface drainage is preferred although sweet sorghum can withstand long waterlogged condition; clay loam is preferred with soil acidity not lower than pH 6.

Land Preparation

Two rotavations at a depth of 25-30 cm is desirable to attain a fine and good soil tilth. This is necessary to have a uniform germination because sweet sorghum seed are small as compared to corn.

Setting of Furrow

Two planting seasons are possible for sweet sorghum. During the wet season, furrows are set 100 cm apart while the dry season planting are set 75 cm apart.

Fertilization

A fertilizer rate of 80-60-60 is generally recommended for a clay loam soil in both seasons. The basal fertilizer is 30-30-30 or 215 kg of 14-14-14 per hectare. This is 21-22g/linear meter of row in the 100 cm spacing and 16g/m in the 75 cm spacing. The fertilizer is drilled at the bottom of the furrow before planting.

Side dressing is done 21 DAE. If ammonium sulfate (21-0-0) is used, the rate is 23-24g/m of row in the 100 cm spacing while 18g/m is applied in the 75 cm spacing. In case urea is used, 11-12g/m is side dressed in the 100 cm row spacing and 8-9g/m in the 75 cm spacing. If the soil is dry, overhead irrigation should follow especially during the dry season with the water directed to the planting furrows only. Since the area between the rows is dry, hilling up using a double-moldboard plow should follow to cover the fertilizer and wet soil. The dry soil cover will serve as “soil mulch”.

Planting

The seeding rate is 5-8 kg ha to attain a population density of 130,000-150,000 plant ha. The seeds are drill-planted by hand or a planter can be used. During the wet season planting, the furrows are set 10 cm deep. The seeds are drill planted at the bottom of the furrow and then spike tooth harrow is passed cover the seeds to a dept of about 2-3 cm.

For the dry season planting, the furrows should be made at least 15-20 cm deep to be able to make use of more residual soil moisture. The seeds are set at the bottom of the furrows but these are not covered anymore if the soil is dry. The impact of irrigation water running through a flexible hose which is directed at the side of the furrow will cover the seeds. In cases where the soil is moist, the technique used during the wet season planting is followed.

Irrigation

Sweet sorghum is remarkably drought-resistant and resists months of dry weather until rains resume. Supplemental irrigation is rarely needed but sweet sorghum needs moisture for uniform seed germination, hence, overhead irrigation is recommended at planting when moisture is insufficient for germination. Each fertilizer application should be followed by irrigation in case there is no rain.

Thinning

For the 75 cm row spacing, maintain 10-11 plants m which is approximately 10 cm between plants. For the 100 cm spacing, 13 plants are maintained per meter of row or about 11 cm between plants. The population density will be 130,000 plants ha in the 100 cm row spacing which is actually the wet season crop and 150,000 plants ha in the 75 cm row spacing which is the dry season crop. Thinning should be done before hilling-up or side dressing the second fertilizer dose which is 14-21 days after emergence.

Crop Protection

So far, plantings are not bothered yet by insect pests and disease. In areas where sweet sorghum are grown for a long time already like India, ICRISAT has reported that shoot fly and stem borer are the major insect pests. Shoot fly attacks soon after germination up to 30 DAP. Stem borer incidence is at a later stage up to maturity. Shoot fly attack is noted by dead hearts in seedlings and profuse tillering in affected plants later. According to ICRISAT shoot fly can be controlled with Carbofuran 3G at 8-10 k ha during planting applied at the bottom of the furrow. The same insecticide could be applied on leaf whorls (2-3 granules/whorl) to prevent stem borer tunneling.

Harvesting

Cut first the panicles. The stalks are cut (similar to sugarcane) as close as possible to the ground leaving one node only. This node will be the sprouting point of the ratoon.

* Seed yield during the second and third rations where not taken due to heavy bird damage.

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For further information, contact:

Dr. Heraldo L. Layaoen
Mr. Mario I. Remolacio
Mrs. Rosemarie G. Ramos
Mariano Marcos State University
Batac 2906 Ilocos Norte
Tel: (077) 792 2558

Dr. Heraldo Layaoen of MMSU is the overall coordinator of the projects, “Commercial Production and Utilization of Sweet Sorghum” and “Commercial Production and Utilization of Pigeon Pea.” MMSU serves as the model site. Interventions and project strategies will be replicated in the identified provinces of Ilocos Norte, Ilocos Sur, La Union, Isabela, Cagayan, Kalinga, Abra, Nueva Ecija, Tarlac, and Pampanga for the full implementation of the project. Photo from cleantechrenewables.com

This entry was posted on Thursday, April 10th, 2008 at 8:51 am and is filed under Plant & Crops. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

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