PARTIAL FACTOR PRODUCTIVITY IN RICE-WHEAT AND RICE-RICE SYSTEMS

Using precise information regarding the quantity of fertilizer applied and yields obtained from seed farms and farmers' fields, nutrient-related partial factor productivity (kg grain/kg NPK applied) was estimated. Under the rice-wheat system, the northwestern zone of the IGP showed positive growth, in contrast to the highly negative growth in the eastern zone (Tables 26-29). Limitation of potassium due to the customary removal of straw for cattle feed appears to be one reason for this negative trend; in the northwestern zone, straw is burnt and the ash incorporated into the soil, resulting in a positive trend.

TABLE 26

Partial factor productivity1 (NPK) growth of rice and wheat in seed farms and on-farm trials under the rice-wheat system in Punjab

	Seed farms
	PFP, PAU, Fathegarh Sahib			PAU, Ropar				KVK, Patiala
	Paddy	Wheat	Total	Paddy		Wheat	Total	Paddy		Wheat	Total
Crop growth rate	1.91	0.54	1.36	-10.70		1.81	-5.25	-0.16		3.72	0.94
Average 1	28.7	20.5	48.7	17.8		10.5	28.1	41.47		19.11	60.58
Average 2	31.2	22.8	53.0	9.9		12.8	21.0	39.57		24.27	63.84
% increase	8.9	11.0	8.8	-44.0		20.9	-25.4	-4.6		27.0	5.4

	On-farm trials
	Dalanpur			Birdwal				Bakshiwala
	Paddy	Wheat	Total	Paddy		Wheat	Total	Paddy		Wheat	Total
Crop growth rate	16.7	23.3	18.5	-11.4		5.6	-5.2	-4.4		5.4	-2.0
Average 1	44.3	13.0	61.0	42.8		18.8	61.6	75.5		23.4	99.0
Average 2	47.4	20.9	68.3	35.1		20.7	55.8	70.7		24.7	95.4
% increase	6.9	60.9	12.0	-17.8		10.0	-9.3	-6.5		5.6	-3.6

¹kg grain/kg NPK.

TABLE 27

Partial factor productivity1 (NPK) growth of rice and wheat in seed farms and on-farm trials under the rice-wheat system in Haryana

	On-farm trials
	Rasulpur 1, Karnal			Kherachapra, Karnal				Rasulpur 2, Karnal				Rasulpur 3, Karnal
	Paddy	Wheat	Total	Paddy		Wheat	Total	Paddy		Wheat	Total	Paddy		Wheat	Total
Crop growth rate	-1.68	-1.89	-1.75	2.97		1.87	2.44	1.65		-0.91	0.54	-1.20		-0.33	-0.83
Mean (1993-95)	31.47	23.60	55.08	26.11		25.38	51.49	32.74		25.38	58.12	32.23		24.11	56.35
Mean (1997-99)	29.42	21.24	50.67	29.65		27.66	57.31	35.03		24.56	59.58	30.53		24.12	54.65
% increase	-0.07	-0.10	-0.08	0.14		0.09	0.11	0.07		-0.03	0.03	-0.05		0.00	-0.03

	On-farm trials								Seed farm
	Rasulpur 4, Karnal			Sikanderpur, Sirsa				DWR, Karnal
	Paddy	Wheat	Total	Paddy		Wheat	Total	Paddy		Wheat	Total
Crop growth rate	-8.04	1.07	-3.98	32.57		2.47	22.52	7.22		0.98	4.03
Mean (1993-95)	32.23	22.33	54.56	28.21		19.23	47.44	20.91		20.23	41.14
Mean (1997-99)	22.75	22.75	45.49	81.90		24.36	106.26	24.31		21.12	45.43
% increase	-0.29	0.02	-0.17	1.90		0.27	1.24	0.16		0.04	0.10

¹kg grain/kg NPK.

TABLE 28

Partial factor productivity1 (NPK) growth of rice and wheat in seed farms under the rice-wheat system in Uttar Pradesh

	GBPUA, Pantnagar			Kanpur, Nagar				Varanasi, UP
	Paddy	Wheat	Total	Paddy		Wheat	Total	Paddy		Wheat	Total
Crop growth rate	0.80	-0.55	-0.11	13.80		1.59	7.44	-3.34		-3.11	-3.13
Mean (1991-93)	45.00	25.83	70.83	13.13		17.65	30.78	18.20		17.71	35.91
Mean (1998-00)	44.54	28.42	72.96	24.15		19.84	43.99	14.72		14.32	29.04
% increase 2	-1.03	-0.27	-0.27	83.92		12.40	42.90	-19.12		-19.12	-19.12

¹kg grain/kg NPK.

²% increase = percentage increase of mean (1998-99 to 1999-00) over mean (1991-92 to 1992-93).

TABLE 29

Partial factor productivity1 (NPK) growth of rice and wheat in seed farms and on-farm trials under the rice-wheat system in Bihar

	SCADA seed farms
	Lodipur (Jahanabad)			Kurtha (Patna)				Samhuta (Rohtas)				Piro (Bhojpur)
	Paddy	Wheat	Total	Paddy		Wheat	Total	Paddy		Wheat	Total	Paddy		Wheat	Total
Crop growth rate	-0.46	-6.31	-2.42	-1.26		-12.86	-0.56	-0.23		-12.15	-4.73	-7.34		-2.08	-5.61
Mean (1992-94)	37.0	17.8	54.7	44.4		28.4	58.6	35.1		24.8	59.9	37.8		16.5	54.2
Mean (1997-99)	34.7	12.6	47.2	37.7		12.0	49.7	31.4		13.2	44.6	23.4		13.8	37.2
% increase 2	-0.06	-0.29	-0.14	-0.15		-0.58	-0.15	-0.10		-0.47	-0.26	-0.38		-0.16	-0.31

	SCADA seed farms												On-farm trial
	Daudnagar (Aurangabad)			Naubatnagar (Patna)				Sabajpura (Patna)				Piro (Bhojpur)
	Paddy	Wheat	Total	Paddy		Wheat	Total	Paddy		Wheat	Total	Paddy		Wheat	Total
Crop growth rate	-1.23	-19.21	-15.55	1.38		-11.00	-2.94	-4.48		-17.19	-11.87	2.79		0.97	2.15
Mean (1992-94)	41.8	27.6	69.4	33.9		24.4	58.3	41.8		28.7	70.5	28.8		15.2	44.7
Mean (1997-99)	16.9	13.3	30.1	34.7		14.7	49.4	30.5		5.9	36.4	32.8		15.7	48.5
% increase 2	-0.60	-0.52	-0.57	0.02		-0.40	-0.15	-0.27		-0.79	-0.48	0.14		0.03	0.09

¹kg grain/kg NPK.

²% increase = percentage increase of mean (1997-98 to 1998-99) over mean (1992-93 to 1993-94).

Interestingly, on-farm data showed a declining trend of partial factor productivity (PFP) in many farms in Punjab and Haryana, possibly because several farmers in the region apply fertilizer at levels far in excess of recommended doses. In the rice-rice system, PFP varied according to the location of the state farm. In Andhra Pradesh, all the seed farms except two showed, respectively, negative and positive growth in kharif and rabi rice, whereas in farmers' fields 8 out of 12 showed positive growth in Godavari Delta (Tables 30 and 31). Such farm-to-farm differences in the same region could be the result of different levels of nutrient management practised by farmers. In Pennar Delta (Nellore), PFP growth was negative for both kharif and rabi rices, warranting the need for site-specific nutrient optimization. In Tamil Nadu, also, PFP for applied nutrients varied depending on the season and farm. Five seed farms located in the major rice-growing districts showed a positive trend for kharif rice, but for rabi rice it was marginally negative (Table 32). In Cauvery Delta, where on-farm site-specific nutrient management is being studied, PFP was positive across many farms, possibly as a result of optimization of applied nutrients (Table 33). The seed farms and farmers in Andhra Pradesh use 5-10 tonnes/hectare (ha) of farmyard manure (FYM) every year, as well as green manuring with residues of summer fodder legume, particularly in the Godavari Delta. Most years, kharif rice is supplemented with FYM or cattle manure. In Tamil Nadu, recycling crop residues and organic manuring are common practice, as in Andhra Pradesh. Differences in the regularity and quantity of organic manure used may be one reason for the farm-to-farm differences observed in partial factor productivity. In Karnataka, PFP growth showed contrasting trends: moderately negative in seed farms for both kharif and rabi rice, and highly positive in kharif season in farmers' fields. This contrast may also be attributed to the farmers' use of organic manure (Table 34).

TABLE 30

Partial factor productivity1 (NPK) growth of kharif and rabi rice in seed farms under the rice-rice system in Andhra Pradesh

	Samalkot (EG)			Garikapadu (Krishna)				Undi (WG)				Kanekal (Anantapur)
	Kharif	Rabi	Total	Kharif		Rabi	Total	Kharif		Rabi	Total	Kharif		Rabi	Total
Crop growth rate	-3.56	-6.48	-4.67	-4.74		6.10	-1.54	0.89		3.31	1.89	2.25		-3.59	-1.06
Mean (1991-93)	32.79	20.74	53.54	29.58		11.79	41.37	26.54		14.80	41.34	12.67		16.93	29.60
Mean (1996-98)	32.04	17.63	49.67	23.71		14.92	38.62	28.50		17.96	46.46	12.11		13.33	25.45
% increase2	-2.31	-15.00	-7.23	-19.85		26.49	-6.64	7.40		21.29	12.38	-4.41		-21.24	8.00

	Palampeta (Warangal)			ARS (Nellore)				ARS (Maruteru, WG)
	Kharif	Rabi	Total	Kharif		Rabi	Total	Kharif		Rabi	Total
Crop growth rate	-2.26	5.35	1.71	0.50		-0.41	0.05	-2.52		0.51	-1.03
Mean (1991-93)	13.40	12.82	26.22	31.94		24.53	56.48	38.46		31.58	70.04
Mean (1996-98)	12.64	15.95	28.59	32.81		24.63	57.43	32.69		32.50	65.19
% increase2	-5.73	24.47	9.03	2.70		0.37	1.69	-15.00		2.92	-6.92

¹kg grain/kg NPK.

²% increase = percentage increase of mean (1996-97 to 1997-98)over mean (1991-92 to 1992-93).

TABLE 31

Partial factor productivity1 (NPK) growth of kharif and rabi rice under rice-rice system in on-farms in Andhra Pradesh

	West Godavari
	Eletipadu 1			Eletipadu 2				CV Palem 1				CV Palem 2
	Kharif	Rabi	Total	Kharif		Rabi	Total	Kharif		Rabi	Total	Kharif		Rabi	Total
Crop growth rate	-2.68	4.60	1.58	-7.33		4.60	-0.45	-3.94		4.53	1.12	-2.04		4.37	1.54
Average 1	56	25	33	40		22	28	171		27	42	188		29	48
Average 2	51	30	35	29		27	28	150		32	44	171		35	52
% increase2	-9.27	19.61	6.74	-26.67		19.61	-2.08	-12.20		20.00	6.25	-8.89		21.57	7.29

	West Godavari
	Kaikaram 1			Poduru 1				Poduru 2				Kavitam 1
	Kharif	Rabi	Total	Kharif		Rabi	Total	Kharif		Rabi	Total	Kharif		Rabi	Total
Crop growth rate	2.14	4.99	3.68	2.88		5.28	4.22	2.85		4.31	3.77	0.23		4.30	2.53
Mean (1993-95)	196	28	46	68		23	32	73		21	32	74		19	30
Mean (1997-99)	212	33	52	74		28	38	85		26	38	80		23	34
% increase2	8.09	17.08	12.98	8.72		23.98	17.23	17.5		19.5	18.6	8.1		17.0	12.8

	West Godavari
	Kavitam 2			Rajula Peta				Kaikaram 2				Akiveedu
	Kharif	Rabi	Total	Kharif		Rabi	Total	Kharif		Rabi	Total	Kharif		Rabi	Total
Crop growth rate	2.65	5.65	4.41	4.46		3.18	3.85	0.64		2.74	1.86	1.19		3.66	2.61
Mean (1993-95)	39	21	27	33		19	24	61		20	29	32		25	28
Mean (1997-99)	45	25	32	41		22	28	66		22	32	36		28	31
% increase2	17.1	20.7	19.0	24.6		11.8	17.5	8.1		13.3	10.9	12.9		15.5	14.3

Year	Nellore
	Kakulapadu			Gangapatnam				Pottepalem			Yallayapalem				Peddacherukuru
	Kharif	Rabi	Total	Kharif		Rabi	Total	Kharif	Rabi	Total	Kharif		Rabi	Total	Kharif		Rabi	Total
Crop growth rate	-3.55	-9.22	-6.18	-7.67		-12.96	-9.99	-6.95	-6.38	-6.69	-11.62		-12.90	-12.23	-3.13		-4.85	-3.82
Mean (1993-95)	30.5	40.0	34.5	38.3		49.0	42.6	34.6	34.1	34.3	39.2		41.7	40.3	31.1		37.2	33.6
Mean (1997-99)	25.5	26.4	25.9	27.2		27.0	27.1	26.2	26.0	26.1	23.4		23.4	23.4	27.7		30.6	29.0
% increase2	-16.3	-34.0	-24.9	-29.1		-44.9	-36.4	-24.1	-23.7	-23.9	-40.2		-43.9	-42.0	-11.0		-17.9	-13.6

¹kg grain/kg NPK.

²% increase = percentage increase of mean (1997-98 to 1998-99) over mean(1993-1994 to 1994-95).

TABLE 32

Partial factor productivity1 (NPK) growth of rice in selected seed farms under the rice-rice system in Tamil Nadu

	TRRI, Aduthurai			Thirunelveli			Tanjore
	Kharif	Rabi	Total	Kharif	Rabi	Total	Kharif	Rabi	Total
Crop growth rate	1.7	1.9	2.7	38.9	5.0	25.9	-1.4	-1.7	-1.5
Mean (1992-93)	25.8	12.0	35.0	-	8.6	-	21.7	17.3	39.0
Mean (1997-98)	28.3	11.3	39.6	-	12.7	-	21.0	16.5	37.6
% increase2	9.5	-5.4	13.1	-	48.3	-	-2.9	-4.4	-3.6

	Kanyakumari			Trichy			Theni
	Kharif	Rabi	Total	Kharif	Rabi	Total	Kharif	Rabi	Total
Crop growth rate	-3.7	-0.1	-2.5	-	9.4	-	-0.8	-2.9	-1.9
Mean (1992-93)	73.5	32.4	105.9	-	11.1	-	10.1	12.2	22.3
Mean (1997-98)	66.4	34.9	101.4	-	15.0	-	9.6	9.7	19.4
% increase2	-9.6	-7.7	-4.3	-	34.8	-	-4.4	-20.1	-13.0

¹kg grain/kg NPK.

²% increase = percentage increase of mean (1997-98) over mean (1992-93).

TABLE 33

Partial factor productivity1 (NPK) growth of rice in selected on-farms under rice-rice system in Tamil Nadu

	Tanjavur
	Ammenpettai 1			Ammenpettai 2				Thirumangalakudi				Thiruvisanalluru				Thugili
	Kharif	Rabi	Total	Kharif		Rabi	Total	Kharif		Rabi	Total	Kharif		Rabi	Total	Kharif		Rabi	Total
Crop growth rate	2.90	-10.83	-	10.38		12.13	-	16.54		5.51	-	-3.19		15.83	-	13.16		5.98	-
Mean (1995-96)	28	35	-	31		-	-	29		26	-	30		21	-	24		21	-
Mean (1999-00)	29	30	-	40		-	-	64		33	-	26		33	-	31		24	-
% increase2	3.73	-13.91	-	26.59		-	-	117.98		26.68	-	-13.52		56.03	-	29.87		12.97	-

	Tanjavur			Nagapattinam
	Koranattukarpur			Tirumannachery				Therazhandur 1				Therazhandur 2				Kshetirabalapuram
	Kharif	Rabi	Total	Kharif		Rabi	Total	Kharif		Rabi	Total	Kharif		Rabi	Total	Kharif		Rabi	Total
Crop growth rate	6.46	1.87	-	14.46		18.71	-	-6.16		3.19	-	27.20		-0.25	-	8.43		15.5	-
Mean (1995-96)	35	29	-	28		20	-	53		31	-	25		29	-	38		26	-
Mean (1999-00)	39	34	-	35		30	-	46		35	-	46		28.4	-	47		39	-
% increase2	12.14	16.18	-	25.52		53.89	-	-13.47		12.54	-	87.58		-2.05	-	22.63		51.46	-

¹kg grain/kg NPK.

²% increase = percentage increase of mean (1999-2000) over mean (1995-96).

TABLE 34

Partial factor productivity1 (NPK) growth of rice in selected seed farms and on-farms under rice-rice system in Karnataka

	Seed farm, RRS Mandya				On-farm trials, Mandya
	Sivalli		VC farm		EEI, Mandya			Sampalli
	Kharif	Rabi	Kharif	Kharif	Rabi		Kharif	Rabi	Total
Crop growth rate	-0.74	-	-1.50	-2.49	-4.01		7.13	-1.13	3.01
Mean (1991-93)	17.99	16.56	22.23	16.29	26.00		20.76	25.91	46.67
Mean (1997-99)	17.17	20.14	20.70	14.00	18.18		28.73	27.30	56.03
% increase2	-4.5	21.6	-6.9	-14.0	-30.1		38.4	5.4	20.0

¹kg grain/kg NPK.

²% increase = percentage increase of mean (1997-98 to 1998-99) over mean(1991-92 to 1992-93).

RECOMMENDATIONS

Over the last 20 years large amounts of data have been generated in India on yield growth and factor productivity trends of rice in rice-wheat and rice-rice cropping systems. Analysis of these data at either macro or experimental levels has not helped to arrive at a definite conclusion regarding either the growth trends or the causal factors for low/negative growth, except for a few leads and broad generalizations. The conflicting and inconsistent results often obtained from macro and experimental studies have made decision-making on corrective measures difficult. The reasons for this situation include a limited database, excessive dependence on macro-level data and wide variation in the level of crop management in relation to biophysical factors at on-farm level. The data sources used for this exercise were at micro level (seed farms and farmers' fields) in addition to macro and experimental level; on this basis, suggestions are given below for follow-up action at national level:

• Identification of biophysical environmental factors contributing to yield stagnation (very low growth rate) and yield decline (negative growth) in high productivity areas, such as selected districts in Punjab and Tamil Nadu, through intensive experimental study at representative locations.
• Initiation of research efforts focusing on optimizing yield and reversing negative yield trends on an experimental basis at a few selected locations in Punjab and Tamil Nadu.
• Strengthening of research to monitor the growth trends and factor productivity in areas approaching high yields giving emphasis to micro-level study.
• Initiating an extensive on-farm study in fixed farms in the target regions, allowing crop diversification/varietal choice and nutrient use according to the farmers' preferences from year to year in otherwise essentially rice-rice and rice-wheat systems, so as to develop yield growth prediction models.
• Promotion of research on the development of higher-yielding varietal and crop production technologies, with special emphasis on hybrid and new plant-type rice varieties and site-specific (precision) integrated nutrient and crop manage-ment for raising yield levels on a sustainable basis in the target areas.

REFERENCES

Ali, M. & Byerlee, D. 2000. Productivity growth and resource degradation in Pakistan's Punjab. Policy working paper. In J.K. Laddha, K.S. Fischer, M. Hossain, P.R. Hobbs, & B. Hardy. Improving the productivity and sustainability of rice-wheat systems of the Indo-Gangetic plains: a synthesis of NARS-IRRI partnership research. IRRI Discussion Paper, No. 40. Los Baños, the Philippines, IRRI.

Cassman, K.G. & Pingali, P.L. 1995. Extrapolating trends from longterm experiments to farmers' fields. A case of irrigated rice systems in Asia. In V. Barnett, R. Payne & R. Steiner, eds. Agricultural sustainability in economic environmental and statistical terms, p. 63-86. London, John Wiley & Sons.

Duxbury, J.M., Abrol, I.P., Gupta, R.K. & Bronson, K. 2000. Analysis of longterm soil fertility experiments with rice-wheat rotation in South Asia, p. 7-22. Rice Wheat Consortium Series No. 6. New Delhi, CIMMTT/IRRI.

Flinn, J.C. & De Datta, S.K. 1984. Trends in irrigated rice yields under intensive cropping at Philippine research stations. Field Crops Res., 9: 1-15.

Hobbs, P.R. & Morris, M.L. 1996. Meeting South Asia's future food requirements from rice-wheat cropping systems. Priority issues facing reseachers in post green revolution era. NRG Paper 96-01. CIMMYT.

Laddha, J.K., Fischer, K.S., Hossain, M., Hobbs, P.R & Hardy, B. 2000. Improving the productivity and sustainability of rice-wheat systems of the Indo-gangetic plains: a synthesis of NARS-IRRI partnership research. IRRI Discussion Paper, No. 40. Los Baños, the Philippines, IRRI.

Murgai, R. 2000. The green revolution and the productivity paradox: evidence from India Punjab. In J.K. Laddha, K.S. Fischer, M. Hossain, P.R. Hobbs, & B. Hardy. Improving the productivity and sustainability of rice-wheat systems of the Indo-Gangetic plains: a synthesis of NARS-IRRI partnership research. IRRI Discussion Paper, No. 40. Los Baños, the Philippines, IRRI.

Nambiar, K.K.M. 1994. Soil fertility and crop productivity under long-term fertilizer use in India. New Delhi, ICAR.

Nambiar, K.K.M. 1995. Major cropping systems in India. In V. Barnett, R. Payne & R. Steiner, eds. Agricultural sustainability: economic, environmental and statistical consideration. p. 133-145. London, John Wiley & Sons.

Regmi, A.P. 1996. Longterm soil fertility trial under rice-wheat rotation. Paper presented at National Winter Workshop, September 1995, Khumullar, Nepal.

Sinha, S.K., Singh, G.B. & Mangala Rai. 1998. Decline in crop productivity in Haryana and Punjab: myth or reality? New Delhi, ICAR Report.

Steiner, R.A. & Herdt, R.W. 1995. The directory of long-term agricultural experiments. Vol. 1. Rome, FAO.

Swaroop, A. & Wanjari, R.H. 2000. Three decades of AICRP on longterm fertilizer experiments to study changes in soil quality, crop productivity and sustain-ability. Bhopal, IISS.

Yadav, R.L, Dwivedi, B.S. & Pandey, P.S. 2000. Rice-wheat cropping system: assessment of sustainability under green manuring and chemical fertilizer inputs. Field Crops Res., 65: 15-30.

Yadav, R.L. 1998. Factor productivity trends in a rice-wheat cropping system under longterm use of chemical fertilizer. Expt. Agri., 34: 1-18.

Yadav, R.L., Gangwar, K.S. & Prasad, K. 1997. Dynamics of rice-wheat cropping system in India. Technical Bulletin. Modipuram, UP, PDCSR.

Yadav, R.L., Yadav, D.S., Singh, R.M. & Kumar, A. 1998. Longterm effects of inorganic fertilizer inputs on crop productivity in a rice-wheat cropping system. Nutr. Cycl. in Agroecosystems, 51: 193-200.

Baisse de rendement et de productivité de la production rizicole intensive en Inde - Une étude de cas

Il est important pour l'Inde de rester autosuffisante durablement en ce qui concerne le riz pour garantir sa sécurité alimentaire. Pour pouvoir maintenir le niveau actuel d'autosuffisance en céréales vivrières, l'Inde devrait augmenter sa production d'environ 35 millions de tonnes, par rapport au niveau actuel, d'ici 2010. Étant donné qu'elle n'a pratiquement aucune possibilité de croissance horizontale, elle devra réaliser ses projections pour la demande uniquement en augmentant son rendement de 2,8 à 3,75 tonnes/ha. Parmi les différentes stratégies envisagées pour atteindre les objectifs de production à venir, la réduction de l'écart entre les rendements potentiels et les rendements effectifs sur l'exploitation et l'optimisation du niveau des rendements dans les zones de culture intensive à forte productivité, sont des solutions intéressantes. Pour y parvenir, il faudra accorder une attention prioritaire au maintien des zones de culture intensive riz-blé et de double ou triple cultures de riz.

Face aux craintes que suscitent le ralentissement de la croissance du rendement et la stagnation ou le déclin de la productivité des facteurs depuis la fin des années 80, on remet souvent en question la durabilité des systèmes de culture riz-blé et riz-riz et l'efficacité des stratégies de production actuelles pour la réalisation des objectifs de production. En l'absence de tendance bien définie résultant des études en cours et passées sur la croissance du rendement et la productivité des facteurs dans les deux principaux systèmes d'exploitation basés sur le riz, la présente enquête a été effectuée. Pour l'étude au niveau macroéconomique, des zones spécifiques ont été choisies sur la base de la productivité relative et de l'intensité des cultures. Les données ont été tirées de sources variées, notamment des rapports, des enquêtes et de la correspondance publiés ou non depuis 18 ans. Pour l'étude de niveau microéconomique, des fermes semencières de l'État et des universités et des champs d'agriculteurs novateurs ont été sélectionnés. Pour l'étude de niveau expérimental, les données tirées d'expériences à long terme ont été utilisées.

Au niveau des États et des districts, l'étude révèle que la productivité des systèmes s'accroît mais à un rythme relativement faible tant pour les systèmes riz-blé que pour les systèmes riz-riz. Dans la plaine du Gange, les résultats montrent que les rendements de riz baissent tandis que les rendements de blé augmentent ou restent stationnaires dans le nord-ouest et les rendements de blé et de riz reculent fortement dans l'est. Une baisse uniforme de productivité des engrais épandus a été constatée dans tous les systèmes, les États et les districts. La croissance accrue de la consommation d'engrais pourrait être la cause, outre l'état de la fertilité naturelle, du déclin observé de la productivité partielle des facteurs (PPF).

L'analyse microéconomique indique des tendances variables pour la croissance du rendement et la PPF dans tous les systèmes. Dans le système de culture riz-riz, les résultats montrent une variation de la croissance du rendement de riz et de la productivité partielle des facteurs d'une exploitation à l'autre en saison humide comme en saison sèche. Il est intéressant de constater toutefois que la croissance de la PPF avec l'application d'éléments fertilisants est positive dans toutes les exploitations et tous les champs probablement grâce à une meilleure gestion des éléments fertilisants. Dans le système de culture riz-blé de la plaine du Gange, les résultats indiquent une croissance positive uniquement marginale de la productivité des systèmes ainsi que des cultures de riz et de blé. Dans plusieurs expériences faites sur l'exploitation dans toute la plaine du Gange, les rendements de blé tendaient à augmenter plus rapidement que ceux de riz dans les plaines du nord-ouest, tandis que dans les plaines du nord-est les rendements de riz restaient plus stables que ceux de blé.

Descenso de los rendimientos y la productividad en los sistemas intensivos de producción de arroz de la India - Un estudio monográfico

El mantenimiento de la autosuficiencia en el abastecimiento de arroz es importante para la seguridad alimentaria de la India. Para garantizar el nivel actual de suficiencia en el abastecimiento de cereales alimentarios, este país tendría que producir en el año 2010 unos 35 millones de toneladas más que las actuales. Sin apenas margen para el crecimiento horizontal, la demanda prevista ha de satisfacerse exclusivamente elevando el nivel del rendimiento desde 2,8 hasta 3,75

t/ha. Entre las diversas estrategias que se contemplan para alcanzar los objetivos de producción futura, se concede especial importancia a la reducción del desfase actual entre los rendimientos agrícolas potenciales y los reales y la optimización del nivel de rendimiento en las áreas de cultivo intensivo y productividad elevada. En este esfuerzo conviene prestar una atención prioritaria al sostenimiento de las áreas en que existe un cultivo intensivo de arroz-trigo y en las que se obtienen dos o tres cosechas de arroz.

Ante los temores que despiertan la desaceleración del crecimiento de los rendimientos y el estancamiento o disminución de la productividad de los factores desde finales de los años ochenta, se ha cuestionado a menudo la sostenibilidad de los sistemas de cultivo arroz-trigo y arroz-arroz, así como la eficacia de las estrategias actuales de producción para alcanzar los valores previstos para esta última. La presente investigación se inició sin que los estudios anteriores y en curso sobre la mejora del rendimiento y la productividad de los factores en los dos sistemas principales de cultivo basados en el arroz hubieran permitido definir tendencias claras. Para poder realizar el estudio a gran escala se seleccionaron algunas zonas específicas en función de su grado relativo de productividad e intensidad de cultivo. Los datos se obtuvieron de diversas fuentes, entre ellas, informes, correspondencia y estudios de los últimos 18 años, publicados e inéditos. Para el estudio a pequeña escala se seleccionaron granjas estatales y universitarias de producción de semillas, así como explotaciones agrícolas avanzadas. Para el estudio experimental se recurrió a datos obtenidos de experimentos a largo plazo.

El estudio revela que la productividad del sistema está aumentando en el ámbito estatal y de distrito, aunque a un ritmo relativamente bajo tanto en los sistemas de cultivo arroz-trigo como en los sistemas de cultivo arroz-arroz. En las planicies del Indo y del Ganges, los resultados indican que en la parte noroccidental los rendimientos del arroz disminuyen, mientras que los del trigo o bien aumentan o permanecen estables, y que en la parte oriental disminuyen rápidamente tanto los del trigo como los del arroz. En los distintos sistemas, estados y distritos se detectó una decreciente productividad generalizada de los abonos utilizados. La aceleración del consumo de abonos podría ser una de las causas, de la disminución observada del factor de productividad parcial, aparte del grado de fertilidad natural y su situación actual.

El análisis a pequeña escala indica la existencia de diversas tendencias en el aumento de los rendimientos y el factor de productividad parcial en los distintos sistemas. En el sistema de cultivo arroz-arroz, se obtuvieron valores distintos, de una explotación agrícola a otra, en el aumento del rendimiento del arroz, y una variación parcial de la productividad de los factores en la estación seca y en la húmeda. Sin embargo, el crecimiento del factor de productividad parcial es positivo en todas las granjas y explotaciones agrícolas, a causa probablemente de una gestión optimizada de los nutrientes. En el sistema arroz-trigo de las planicies del Indo y del Ganges, se registró un crecimiento positivo marginal de la productividad del sistema y de los cultivos de arroz y trigo que lo componen. En varios experimentos agrícolas realizados en la región, el rendimiento del trigo tendía a mostrar un índice de crecimiento ligeramente más elevado que el del arroz en las planicies noroccidentales, mientras que en las nororientales los rendimientos del arroz continuaban siendo más estables que los del trigo.