Improved N and P fertilizer management increases the rice yields of small resource-poor farmers

"S.Y. Daftardar^a, S.M. Wagle^band N.K. Savant^c

^a Janaseva Foundation, Dadra 396230, Union Territory of DNH, India;
^b Bharatiya Agroind. Foundation, Jawhar, 401603 Dist.Thane, Maharashtra, India;
^c StaSav International, 2551 Hough Road, Florence, AL 35630, USA

The deep point-placement of nitrogen (N) as pillow-shaped urea briquettes (UB) after transplanting is an efficient N management practice in rice. But, the conventional basal application of water-soluble phosphorus (P) such as single superphosphate (SSP) is not an environmentally friendly fertilizer management practice because P in the floodwater and sorbed by clays in the surface soil is prone to surface runoff losses. There is an urgent need for simple, efficient and still affordable NP fertilizer management that small resource-poor farmers can use to increase the productivity of their small, fragmented, lowland paddy fields in rainfed regions. Using conventional prilled urea (PU) and diammonium phosphate (DAP), the authors prepared UB containing DAP (UB-DAP) (4:1, N:P) and evaluated their agronomic potential as an NP source for rainfed transplanted rice during the 1993, 1994 and 1995 wet (southwest monsoon) seasons on tribal farmers' gelds in a warm subhumid tropical region on the west coast of Maharashtra State, India.

Three methods of fertilizer management were evaluated in 117 field trials:

• Improved management. UB-DAP were deep-placed by hand on the day of transplanting using a modified 20 x 20 cm spacing. This hill spacing facilitates the effective and speedy hand-placement of UB and was achieved by using the farm-made Bamboo guide transplanting method or the simple-to-use, labour-saving, two-row transplanting method. One 2.7 g UB-DAP placed per four hills supplied 56 kg N/ha and 14 kg P/ha.
• Conventional management. Nitrogen as PU was applied in two splits (one-half basal and one-half top-dressing at the panicle initiation stage), and all P as SSP was the basal application prior to random transplanting.
• Farmers' management. Traditional methods of random transplanting and fertilizer application were evaluated. The average plot size was about 100 m2 and the duration of rice cultivars used ranged from 110 to 135 days. Four- to five-week-old seedlings that had been prepared by the farmers were transplanted in the ratio of five to six seedlings per hill for the improved management trials.

For the first two methods, the plant population and seedlings per hill were not controlled. All other agronomic inputs and operations were the same for a given trial and field operations were managed by the farmers participating using their limited skills and resources.

The southwest monsoon rainfall for the 1993 wet season was average (2 800 mm) and well distributed throughout the growing season (from July to October), whereas during the 1994 and 1995 seasons it was above average but not properly distributed. Despite the marked differences in the rainfall distribution patterns, the improved management of UB-DAP significantly increased the grain and straw yields compared with the conventional management of PU+SSP and was distinctly superior to the farmers' management in the three seasons (see Table).

The increase in yields helped farmers achieve yield potentials of the improved varieties using about 40 percent less fertilizer compared with locally recommended NP rates of fertilizers and with a 30 to 35 percent lower plant population (25 hills/m2 versus 36 to 39 hills/m2 observed in random transplanting). The use of the modified 20 x 20 cm spacing showed a potential reduction of up to 50 percent of the labour normally required for the UB placement by hand (four to six workdays/ha versus eight to ten workdays/ha when standard 20 x 20 cm spacing is used).

Average rice yields of farmer-managed field trials as influenced by the improved management of UB-DAP vis-�-vis the conventional and farmers' managements of PU+SSP on the west coast of Maharashtra State, India (1993-1995 wet seasons)

Note: LSD (P = 0.05).

n = Number of field trials. Fertilizer rates: 56 kg N/ha + 14 kg P/ha. Average yields for a given season followed by the same letter are not significantly different from each other.

Estimated value. The cost ratio (VCR = value of additional grain and straw yields/all additional variable costs of UB-DAP fertilizer, labour for its placement etc.) for the improved management of UB-DAP compared with the farmers' management ranged from 5 to 8.5. These attractive VCRs increased by 2 to 3 when the potential seed saving owing to the lower hills/m2 for the improved management was considered. VCRs for the conventional management of PU+SSP were up to 2.9 and economically less attractive (a VCR of 3 is considered to be the minimum adoption of the new fertilizer practice of farmers in the rainfed region). Stochastic dominance (probability) analysis of the three-year grain yield data suggests that the improved management of UB-DAP is a risk-free practice and therefore would be accepted by small farmers and also preferred by policy-makers.

Despite the 15 to 20 percent estimated extra cost of producing UB-DAP fertilizer at the village level using a portable fertilizer briquetter (developed by the International Fertilizer Development Centre, Muscle Shoals, Alabama, USA) and the additional labour cost of its placement by hand, the majority of the farmers participating were impressed by the overall agronomic, economic, social and environmental benefits of the improved management of UB-DAP. They, therefore, expressed their willingness to adopt the UB-DAP fertilizer management provided proper fertilizer is available in local markets at affordable prices and women farmers are trained for its placement in the fields.

In conclusion, the improved management of UB-DAP has the potential to enhance the rice production of rainfed lowland ecoregions of developing countries with the minimum financial risk and environmental concern.

Acknowledgements. Financial assistance in part by the International Fertilizer Development Center, Muscle Shoals, Alabama, USA for conducting the 1993 field trials and field assistance from the staff of Vanvasi Kalyan Ashram, Maharashtra, India for the 1993-95 trials are appreciated.

UNE MEILLEURE GESTION DES ENGRAIS N ET P ACCRO�T LES RENDEMENTS DE RIZ DES FERMIERS � FAIBLES RESSOURCES ET PAUVRES

Une mani�re efficace de g�rer l'azote (N) en riziculture est de placer ponctuellement en profondeur des briquettes d'ur�e en forme de coussin (UB) apr�s la transplantation. Toutefois, l'�pandage basal traditionnel de phosphore (P) soluble dans l'eau comme le superphosphate simple ne constitue pas une gestion respectueuse de l'environnement parce que le phosphore contenu dans l'eau et celui adsorb� sur les argiles sont soumis � des pertes par ruissellement. Il faut obtenir d'urgence une gestion des engrais NP simple, efficace et pourtant abordable pour les petits fermiers ayant peu de ressources afin d'accro�tre la productivit� de leurs petits champs fragment�s dans les bas-fonds des r�gions pluviales.

L'UB contenant du phosphate d'ammonium (UB-DAP) (4: 1, N:P) a fait l'objet d'exp�rimentations qui ont montr� qu'avec une meilleure gestion, l'UB-DAP est susceptible d'am�liorer la productivit� du riz dans les �cor�gions pluviales de bas-fonds des pays en d�veloppement au prix d'un risque financier et �cologique minimal.

LA MEJORA EN LA ADMINISTRACI�N DE FERTILIZANTES N Y P AUMENTA LOS RENDIMIENTOS DEL ARROZ PARA PEQUE�OS AGRICULTORES CON POCOS RECURSOS

La aplicaci�n en profundidad de nitr�geno en forma de briquetas de urea despu�s del trasplante es una pr�ctica eficiente para suministrar N al arroz. El abonado convencional de fondo con f�sforo soluble en agua en forma de superfosfato simple no es una pr�ctica ecol�gicamente id�nea para administrar fertilizantes, ya que el f�sforo disuelto en el agua y absorbido por las arcillas del suelo superficial es propenso a p�rdidas por escorrent�a de superficie. Se necesita con urgencia un sistema sencillo y eficaz, pero asequible, de administraci�n de fertilizantes N y P que pueda ser utilizado por los peque�os agricultores con pocos recursos para aumentar la productividad de sus arrozales de tierras bajas, peque�os y fragmentados, en regiones de secano.

Ensayos realizados con briquetas de urea que conten�an bifosfato am�nico han demostrado que puede aumentar la productividad del arroz en ecosistemas de tierras bajas de secano de pa�ses en desarrollo con un riesgo financiero y un impacto ambiental m�nimos.