RESEARCH AND APPLIED TECHNOLOGY

RECHERCHE ET TECHNOLOGIE APPLIQUÉE

INVESTIGACIÓN Y TECNOLOGÍA APLICADA

Studies on yield maximization through balanced nutrient ratios in irrigated

S.V. Subbaiaha, K. Ramamuoorthyb, R.M. Kumarc and S.P. Singhd

aPrincipal Scientist, bPost-doctoral Fellow, cScientist and dSenior Scientist, Division of Agronomy, Directorate of Rice Research, Rajendranagar, Hyderabad, India

INTRODUCTION

Rice (Oryza sativa L.) is grown in India over a gross area of 42.3 million hectares (ha). The total production in 1998-99 was about 87 million tonnes. However, India would need to produce at least 200 million tonnes of paddy to meet its ever-growing population requirements, and this figure would have to increase by almost 75 percent by 2020. Rice occupies a pivotal position in relation to food security in India. The future of food security in this region will depend on its ability to improve rice productivity continuously on an ecologically sustainable basis. One of the main reasons for low rice productivity in India is the variation in fertilizer usage between the country's different agroclimatic zones and between states in each region. Low input use in general is a further factor accounting for the plateau or declining trend of grain yields.

With the aim of maximizing yields, a number of trials have been conducted throughout the country in various coordinating centres. In recent years the trials revealed that imbalanced nutrient use is the principal cause of the current stagnation in yield levels. It was further found that yield levels could be restored by applying a combination of organic and inorganic fertilizer with micronutrients to crops planted under optimum plant density. Despite the adoption of these practices, yield maximization results in multilocation trials were not consistent. The trials were reconstituted and conducted during 1996 and 1997 incorporating the different NPK ratios along with a balanced nutrients ratio of 4:2:1 NPK/ha, to develop a suitable package of practices for breaking the stagnation and maximizing the grain yield in the lowland rice ecosystem.

METHODS

The multilocation trials, comprising eight treatments (Table 1) laid out in a random block design with three replications, were repeated for two years (1996 and 1997 kharif seasons). They compared the standard NPK ratio of 4:2:1 with different NPK ratios alone and in combinations with farmyard manure (FYM), green manure (GM) or greenleaf manure (GLM) in irrigated transplanted rice. A seed rate of 60-70 kg/ha was used on 20 × 10 cm, 20 × 15 cm, 15 × 15 cm or 15 × 10 cm row spacings. Recommended agronomic practices such as gap filling, weeding and pest and disease control were carried out uniformly as and when needed.

RESULTS

Grain yield differences among the treatments were not significant at Rajendranagar, Mandya, Pattambi, Karjat, Pondicherry, Kapurthala, Patna, Malan, Rewa, Siruguppa, Arundhatinagar, Ghaghraghat and Wangbal in either 1996 or 1997. However, four out of 16 experi-ments in different centres exhibited significant differences in grain yield among the treatments (Tables 1 and 2). At Aduthurai (Tamil Nadu) in clay loam soils, the variety ADT-38 responded well to NPK fertilizer ratio of 2.5:1:1 (150:60:60 kg NPK/ha) in conjunction with 10 tonnes/ha FYM and foliar spray of di-ammonium phosphate (DAP) 2 percent and potassium chloride (KCL) 1 percent at booting and panicle initiation stages with an optimum spacing of 20 × 10 cm registering a maximum grain yield of 6.78 tonnes/ha and 6.92 tonnes/ha, respectively during 1996 and 1997, which was significantly superior to the grain yield obtained under 4:2:1 NPK ratio treatment (240:120:60 NPK kg/ha). The increased yield in the above treatment might be the result of higher production of panicles and panicle weight.

TABLE 1

Grain yield and ancillary characters of rice from yield maximization trials under irrigated conditions, kharif season, 1996

Note: DAP = diammonium phosphate; FYM = Farmyard manure; KCL = potassium chloride; NS = not significant; S = sulphur; Zn = zinc sulphate.

TABLE 2

Grain yield and ancillary characters of rice from yield maximization trials under irrigated conditions, kharif season, 1997

Note: DAP = diammonium phosphate; FYM = Farmyard manure; KCL = potassium chloride; NS = not significant; S = sulphur; STCR = Soil test crop response rate; Zn = zinc sulphate.

At Pusa (Bihar), in silty clay soils, the variety Sujata produced a maximum grain yield of 4.84 tonnes/ha in 1996 and 5.25 tonnes/ha in 1997 under the treatment receiving 10 tonnes/ha of FYM with a fertilizer ratio of 3:1.5:1 (120:60:40 kg NPK/ha) and an optimum population (of 4.3 lakh plants/ha). These results were significantly superior to those obtained using the recommended NPK ratio of 4:2:1 (80:40:20 kg NPK/ha), indicating the importance of organic manure to these soils during 1996 and 1997.

In clay soils at Raipur (Madhya Pradesh), an optimum plant stand (15 × 10 cm) and fertilizer dose of 90:60:40 kg NPK/ha (2.25:1.5:1) with FYM applied at 10 tonnes/ha recorded a maximum grain yield of 7.55 tonnes/ha and 6.37 tonnes/ha in 1996 and 1997, respectively. These yields were significantly superior to those obtained with the 4:2:1 ratio of 90:45:22.5 kg NPK/ha and also other treatments, indicating the positive effect of organic manuring. The increased yield in this treatment combination suggests that the recommended dose of NPK alone was not sufficient to sustain the higher productivity of rice under irrigated conditions.

At Titabar (Assam), in acidic silty loam soils, applying fertilizers based on soil test values of 60:20:40 kg NPK/ha (3:1:2) and 80:40:40 kg NPK/ha (2:1:1), recorded yields of 5.40 tonnes/ha in 1996 and 4.10 tonnes/ha in 1997, which were significantly superior to the yield produced from the treatment applying the recommended NPK dose of 40:20:20 (2:1:1) kg/ha in both the seasons.

DISCUSSION

From the above results, increased yield and yield attributes in 4 out of 16 centres indicated that the normal recommended dose of 4:2:1 NPK ratio failed to increase the grain yield of rice; the results point to the conclusion that the ratio 4:2:1 alone will not always be appropriate for all locations. In some centres, neither a higher dose of NPK nor the recommended dose applied alone influenced the yield. In most cases (12 locations), extra yields were most probably secured by the addition of organic manure, particularly at the rate of 10 tonnes/ha of FYM, along with optimum plant stand. Hence, by maintaining optimum plant population and resorting to the use of organo-inorganic combinations of a suitable ratio of NPK fertilizers with or without foliar or micronutrients, it is possible to maximize the grain yield of irrigated rice with an increased production of panicles per unit area.

In conclusion, mean maximum grain yields in rice under irrigated conditions were achieved by changing the normal recommended NPK dose of 4:2:1 to location-specific soil-based crop-response rate recommendations, with or without additional FYM application. The increases obtained were 1.10, 1.10, 0.74 and 0.33 tonnes/ha at Aduthurai, Pusa, Raipur, and Titabar respectively under 2.5:1:1 NPK ratio plus foliar spray of 2 percent DAP and 1 percent KCL with 10 tonnes/ha of FYM; 11:5.1 NPK ratio with 10 tonnes/ha FYM; 3:2:1 NPK ratio with 10 tonnes/ha FYM; and 2:1:1 NPK ratio on a soil-test crop-response rate basis, respectively, over the normal recommended fertilizer ratio of 4:2:1 during both the years of experimentation in the rainy season. The results underline the importance of location-specific recommendations of balanced NPK nutrients in conjunction with the application of organic manure, and an optimum plant density.

Étude de la maximisation des rendements par l'application de taux d'éléments fertilisants équilibrés dans la culture de riz aquatique irrigué

L'avenir de la sécurité alimentaire de l'Inde dépendra de notre aptitude à améliorer continuellement la productivité des cultures de riz, dans le respect de l'environnement. Une des principales raisons de la faible productivité du riz est le déséquilibre de l'emploi d'engrais entre les différentes zones agroclimatiques du pays. Des essais ont été effectués en 1996 et 1997 pour comparer le taux standard de 4:2:1 NPK à d'autres traitements pour la gestion des éléments fertilisants. Les résultats ont indiqué que la dose normale recommandée de 4:2:1 NPK ne permet pas d'accroître le rendement du grain. Cependant, dans la plupart des cas, les rendements accrus obtenus par adjonction d'engrais organique en particulier 10 tonnes/ha de fumier ne sont sans doute qu'une des raisons avec l'emploi de souches optimales.

Estudios de optimización del rendimiento mediante proporciones equilibradas de nutrientes en el arroz de regadío de tierras bajas

El futuro de la seguridad alimentaria de la India dependerá de su capacidad para lograr una mejora continua de la productividad del arroz a partir de una base ecológicamente sostenible. Una de las razones principales de la baja productividad del arroz son los desequilibrios en la utilización de abonos entre las distintas zonas agroclimáticas del país. Durante 1996 y 1997 se realizaron pruebas con el fin de comparar la proporción estándar 4:2:1 de NPK con otros tratamientos distintos de la gestión de los nutrientes. La dosis normal recomendada, una proporción de NPK de 4:2:1, no conseguía aumentar el rendimiento del grano. En la mayoría de los casos en los que se lograba un rendimiento superior, la única posibilidad era la adición de estiércol orgánico, sobre todo en una dosis de 10 t/ha, siempre que el estado de las plantas fuera óptimo.