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Yield and factor productivity trends in intensive rice production systems in India: a case study

E.A. Siddiq, K.V. Rao and A.S.R. Prasad

Directorate of Rice Research, Rajendranagar, Hyderabad, India

INTRODUCTION

Since achieving self-sufficiency in rice in the early 1980s, India has successfully sustained this situation. However, given the absence of many of the favourable growth factors of the 1970s and 1980s and indicators of decreasing production growth over the last ten years (by about 60 percent), meeting the projected demand of 104 million tonnes of milled rice by the year 2010 without undue environmental and economic cost is the most challenging task. As there is minimal scope for horizontal growth, raising the current yield levels closer to the genetic ceiling and raising the ceiling itself are the only means for future growth. The sizeable gap known to exist between achievable and actual yields in nearly all the rice-growing states is a potential opportunity for raising the yield level in the long term (Table 1).

TABLE 1

Yield gap in major rice-growing states, 1990/91-1997/98

State		Paddy yield (kg/ha)				Yield difference (kg/ha)		Gap of (1) over (2)
		State average (1)		Experimental trial average1 (2)
South zone
Tamil Nadu		4 460		5 286		826		15.6
Andhra Pradesh		3 767		5 882		2 115		36.0
Karnataka		3 456		5 250		1 794		34.2
Kerala		2 857		5 690		2 853		49.8
North zone
Punjab		5 042		6 460		1 418		22.0
Haryana		4 074		7 396		3 322		44.9
Uttar Pradesh		2 870		6 598		3 728		56.5
East zone
West Bengal		3 147		5 003		1 856		37.1
Orissa		1 993		5 620		3 627		64.5
Bihar		1 811		6 083		4 272		70.2
Assam		1 954		6 437		4 483		69.6
Eastern Uttar Pradesh		1 881		6 598		4 717		71.5
Manipur		3 233		7 619		4 386		57.36
Tripura		2 932		6 331		3 399		537
West zone
Maharashtra		2 380		4 501		2 121		47.1
Gujarat		2 146		5 557		3 411		61.4
Madhya Pradesh		1 581		4 710		3 129		66.4
Rajasthan		1 582		6 485		4 903		75.6
Northwestern hills
Jammu and Kashmire		2 774		7 254		4 480		61.8
Himachal Pradesh		1 976		5 003		3 027		60.5
All India		2 759		5 781		3 022		52.3

¹Mean yield of best entry (irrigated medium) at AICRIP test locations over a seven-year period.

More serious effort is needed to ascertain the widely apprehended deceleration of yield and factor productivity in the intensively cropped irrigated ecologies and to initiate research to identify the causal factors for correction. Long-term fertilizer trials established in the early 1970s with the primary objective of assessing the sustainability of intensively cropped systems, such as rice-wheat and rice-rice, indicated declining rice yields and factor productivity at constant input levels. Intensive studies were subsequently undertaken at macro and on-farm experimental levels by various organizations, including the Project Directorate of Cropping Systems Research of the Indian Council for Agricultural Research (ICAR); network research on rice-wheat systems sponsored by the International Rice Research Institute (IRRI) and International Maize and Wheat Center (CIMMYT); and an exclusive study on reversing the declining productivity trends in rice-rice systems by IRRI. Although the studies broadly concurred on the existence of a steady decrease in yield growth over time, no consistent trend was established. In the light of the past research findings on the productivity growth of rice in the two cropping systems, the present study was undertaken with the objective of gaining further insight into this subject.

STUDY APPROACH

The study was planned and carried out at macro-, micro- and experimental levels in the Indo-Gangetic plains (IGP) and peninsular India, representing, respectively, rice-wheat and rice-rice systems. In view of the magnitude of the subject and vastness of the area under the two cultivation systems, specific zones were selected on the basis of relative productivity level and cropping intensity (Tables 2 and 3): Punjab, Haryana, Uttar Pradesh and Bihar broadly covered the western, central and eastern zones of the IGP in respect of rice-wheat; three states, namely, Andhra Pradesh, Tamil Nadu and Karnataka in peninsular India, covered rice-rice. One to six districts were selected in each state (Gurdaspur, Patiala and Ludhiana in Punjab; Jind, Karnal and Kurukshetra in Haryana; Bareilly, Nainital, Shaharanpur, Gorakhpur, Faizabad and Varanasi in Uttar Pradesh; and Patna, Aurangabad, Bhozpur and Samastipur in Bihar under the rice-wheat system; and West Godavari, Nellore and Kurnool in Andhra Pradesh; Thanjavur, Tiruchinapalli, Tirunalvelli and Kanyakumari in Tamil Nadu; and Mandya in Karnataka under the rice-rice system). The data were accessed from various sources including published and unpublished reports from research centres, state Departments of Agriculture and ICAR institutes, in addition to personal surveys and correspondence. The period of study covered the 18 years 1981/82 to 1998/99 with emphasis on the 1990s.

TABLE 2

Agro-ecological features of selected states and districts under the rice-wheat cropping system in the Indo-Gangetic plains, 1997-98

State/district	Yield (kg/ha)		Irrigated areas (%)1		Cropping intensity (%)1
	Paddy	Wheat	Rice	Wheat
Punjab
Gurdaspur	4 220	3 759	-2	-	-
Ludhiana	5 738	4 199	-	-	-
Patiala	5 009	4 060	-	-	-
State	5 196	3 852	99.1	97.1	187.3
Haryana
Karnal	4 261	3 992	-	-	-
Kurukshetra	4 628	3 820	-	-	-
Jind	4 148	3 605	-	-	-
State	4 196	3 660	99.4	98.4	166.6
Uttar Pradesh
Bareilly	3 467	2 740	-	-	-
Nainital	3 713	2 960	-	-	-
Shahranpur	3 995	2 848	-	-	-
Faizabad	3 362	2 530	-	-	-
Gorakhpur	2 850	2 384	-	-	-
Varanasi	3 907	2 344	-	-	-
State	3 222	2 418	62.3	92.5	148.2
Bihar
Aurangabad	3 249	2 136	-	-	-
Bhozpur	3 589	2 857	-	-	-
Patna	2 650	2 373	-	-	-
Samastipur	1 344	2 020	-	-	-
State	2 043	1 999	40.2	88.4	136.9

¹1995-96.

² - = not available.

TABLE 3

Agro-ecological features of selected states and districts under the rice-rice cropping system in peninsular India, 1997-98

State/district	Yield (kg/ha)			Irrigation (%)1	Cropping intensity (%)
	Wet season		Dry season
Andhra Pradesh
West Godavari	3 827	5 270		-	-
Nellore	3 918	4 484		-	-
Kurnool	4 023	4 001		-	-
State	3 473	4 107		94.8	122.6
Tamil Nadu
Thanjavur	5 408	3 737		-	-
Tiruchinapalli	5 648	4 857		-	-
Tirunalvelli	5 601	5 484		-	-
Kanyakumari	5 451	5 928		-	-
State	5 345	4 463		92.0	117.3
Karnataka
Mandya	3 828	4 806		-	-
Shimoga	-	-		-	-
State	3 447	4 128		66.8	114.8

¹As paddy.

For the micro-level study, a new approach was chosen, with state and university seed farms and progressive farmers' fields representing different regions in each of the states. In the absence of planned long-term on-farm experimentation, seed farms and farmers' fields were considered reliable alternatives for data-sourcing. The large seed farms are used exclusively for breeder, foundation and certified seed production of notified crop varieties. Invariably, the same fields are used year after year for the seed production of specific crops. The farms systematically maintain information on the basis of year, season and plot with regard to the crop and variety raised, inputs used, yields obtained, etc. Similarly, progressive farmers also record crop production details for their fields. Care was taken to choose farms and farmers' fields that had practised over the last seven to ten years rice-wheat cultivation in the IGP and rice-rice cultivation in peninsular India (Tables 4 and 5). Proformas exclusively prepared for farms and seed farms were used for data collection.

TABLE 4

Features of seed farm and on-farm sources under the rice-wheat system in the Indo-Gangetic plains

	Number			Straw management		Organic management (years)		Summer crop
	Seed farm		On-farm	Seed farm	On-farm	Seed farm	On-farm	Seed farm	On-farm
Punjab	3		3	Burnt (2)	Burnt	Nil	3	Mung (1)		Potato
Haryana	2		6	Burnt (1)	Burnt	Nil	2-3	Mung (1)		Mung
Uttar Pradesh	3		-	Ploughed (1)	Removed	Nil	-	-		-
Bihar	7		1	Removed	Removed	-	-	-		-

TABLE 5

Features of seed farm and on-farm sources under the rice-rice system in peninsular India

	Number		Organic manuring (years)		Summer crop
	Seed farm	On-farm	Seed farm	On-farm	Seed farm	On-farm
Andhra Pradesh	7	17	1	2	Fallow	Pulses
Tamil Nadu	5	10	1-2	1-2	Pulses	Legumes
Karnataka	3	1	1	1	-	Fallow

For the experimental-level study, data were obtained from long-term experiments for the assessment of nutrient requirements of the component crops and the system. These were used to evaluate the long-term effect on soil fertility and crop productivity, and also to investigate the growth trend of rice yield vis-à-vis system productivity and partial factor productivity under the two systems. Data from the long-term experiments in the IGP conducted at Ludhiana, Karnal and Pantnagar (the northwestern zone of the plains) and at Kanpur, Faizabad, Varanasi and Sabour (eastern zone), and for the rice-rice system, data from long-term experiments conducted by AICRIP, AICARP, AICRP-LTFE (ICAR) at Maruteru (Godavari Delta), Hyderabad and Nandyal in Andhra Pradesh and Thanjavur (Cauvery Delta) in Tamil Nadu, were used for experimental-level analysis.

Partial factor productivity specific to fertilizer nutrient (kg grain harvested/kg NPK applied) was computed using data from seed farm and on-farm sources. This contrasted with the computation done at macro level by earlier workers, which is not reliable because of the lack of precise information on fertilizer consumed by the component crops and the system and on produce obtained for each season.

YIELD GROWTH IN THE RICE-WHEAT SYSTEM

Macro-level study

The study of rice yield and system productivity (rice + wheat) growth in all states except Haryana, representing upper, central and lower zones of the IGP, revealed an increasing trend (Tables 6 and 7). The pace of growth, however, varied according to the state, regions within the state and component crops. Compared to the very low growth rate of rice (0.59 and 0.19 percent) and system productivity in the trans-Gangetic zone (Punjab and Haryana), it was moderately high (2.81 percent) and high (3.80 percent) in Uttar Pradesh and Bihar, respectively, over the 18-year period (1981/82-1998/99).

TABLE 6

Yield growth (tonnes/ha) of rice, wheat and total productivity in selected states under the rice-wheat system in the Indo-Gangetic plains, 1981/82-1998/99

	Punjab				Haryana			Uttar Pradesh			Bihar
	Paddy		Wheat	Total	Paddy	Wheat	Total	Paddy	Wheat	Total	Paddy	Wheat	Total
Crop growth rate (1981-98)	0.59		1.89	1.14	0.19	2.74	1.35	3.80	2.46	3.15	2.81	2.40	2.60
Crop growth rate(1981-90)	0.72		2.78	1.58	0.56	3.67	1.89	5.82	1.81	3.93	5.14	2.00	3.49
Crop growth rate(1990-98)	-0.35		0.76	0.16	-1.70	0.87	-0.41	2.56	1.28	1.97	6.31	0.69	3.21
Mean (1981-83)	4.58		2.98	7.55	3.81	2.57	6.38	1.66	1.73	3.38	1.11	1.41	2.52
Mean (1988-90)	5.05		3.65	8.71	4.13	3.33	7.46	2.68	2.11	4.79	1.82	1.72	3.54
Mean (1990-92)	4.99		3.86	8.84	4.12	3.60	7.72	2.63	2.33	4.96	1.30	1.89	3.19
Mean (1996-98)	4.96		4.08	9.04	3.78	3.79	7.57	3.08	2.50	5.58	1.97	1.99	3.97
% increase 11	10.5		22.8	15.3	8.49	29.57	16.99	61.73	22.17	41.55	64.38	21.91	40.58
% increase 22	-0.5		5.8	2.3	-8.19	5.20	-1.94	16.89	7.55	12.51	51.49	5.70	24.41
% increase T3	8.5		37.1	19.8	-0.7	47.4	18.7	85.8	45.2	65.1	78.6	41.5	57.8
Contribution %	66.6		79.9		49.2	71.9		96.1	89.0		89.4	80.3

¹% increase 1 = percentage increase of mean (1988-90) over mean (1981-83).

²% increase 2 = percentage increase of mean (1996-98) over mean (1990-92).

³% increase T = percentage increase of mean (1996-98) over mean (1981-83).

The growth rates of rice and system productivity during the 1990s compared to those in the 1980s, however, registered a sharp decline to a very low level with signs of a negative trend in the western zone. In Uttar Pradesh, although the decline persisted through the 1990s, it was moderate, unlike in Bihar, where both rice and system productivity registered a quite high growth rate (6.31 and 3.21 percent). As for the influence of the component crops on changes in system productivity, wheat appeared to influence most in the western zone and rice in the eastern zone.

District-level findings reflected a similar trend, with all the districts in the western region showing invariably very low positive to negative growth during the 1980s and 1990s (Table 7). Significant linear growth (1981-99) was not seen in any of the three districts in Punjab and, disturbingly, Ludhiana District registered negative growth. In Haryana, Karnal District again showed growth stagnation at a very low level. The impact of low growth in Karnal District (possibly due to the very large area under low-yielding traditional basmati rice for export) is seen at state level. The growth pattern of the region, especially in Punjab State, suggests that yield levels of rice are unlikely to increase using currently available varietal technology. This conclusion reinforces the earlier findings from yield gap analysis. Serious research and development efforts should be made to develop and popularize varietal technologies of higher ceiling to present genetic yield. Although hybrid rice is one potential technological option for such areas, hybrids ideally suited to this region have not yet been developed. The negative trend observed in some of the districts, especially Ludhiana, warrants further in-depth study to identify and correct the biophysical causal factors, as there is no evidence to substantiate genetic deterioration of varieties (Table 7).

TABLE 7

Yield growth (tonnes/ha) of rice, wheat and total productivity in selected districts under the rice-wheat cropping system in the Indo-Gangetic plains, 1981/82-1998/99

	Punjab
	Gurdaspur					Ludiana							Patiala
	Paddy	Wheat		Total		Paddy		Wheat			Total		Paddy		Wheat			Total
Crop growth rate (1981-98)	0.45	2.75		1.46		-0.56		1.69			0.35		-0.16		1.97			0.77
Crop growth rate (1981-90)	-0.46	2.86		1.00		-0.38		2.74			0.87		1.15		3.39			2.07
Crop growth rate (1990-98)	0.83	2.39		1.56		-0.38		0.39			-0.03		-1.62		0.80			-0.48
Mean (1981-83)	3.64	2.43		6.08		6.05		3.45			9.50		4.92		3.03			7.95
Mean (1988-90)	3.68	3.11		6.78		5.56		4.17			9.74		5.00		3.87			8.87
Mean (1990-92)	3.92	3.27		7.19		5.44		4.26			9.70		5.00		4.06			9.06
Mean (1996-98)	4.18	3.84		8.02		5.57		4.44			10.01		4.59		4.29			8.88
% increase 11	0.9	27.7		11.7		-8.1		20.9			2.5		1.7		27.6			11.6
% increase 22	6.7	17.3		11.5		2.4		4.3			3.2		-8.4		5.8			-2.0
% increase T3	14.7	57.8		32.0		-8.0		28.7			5.3		-6.8		41.7			11.7
	Haryana
	Jind					Karnal							Kurukshetra
	Paddy	Wheat		Total		Paddy		Wheat			Total		Paddy		Wheat			Total
Crop growth rate (1981-98)	1.53	3.72		2.52		-0.07		2.60			1.14		1.32		2.46			1.82
Crop growth rate (1981-90)	-0.36	5.59		2.27		-0.74		3.85			1.27		-0.58		4.48			1.65
Crop growth rate (1990-98)	0.19	0.97		0.61		-1.24		-0.04			-0.63		-0.32		0.41			0.03
Mean (1981-83)	3.33	2.20		5.53		4.03		2.67			6.70		4.04		2.73			6.78
Mean (1988-90)	3.53	3.36		6.88		3.80		3.58			7.38		3.82		3.73			7.55
Mean (1990-92)	4.03	3.48		7.51		4.08		3.86			7.94		4.61		3.81			8.42
Mean (1996-98)	4.34	3.74		8.08		4.26		3.99			8.25		4.77		3.94			8.71
% increase 11	6.1	52.4		24.5		-5.7		34.0			10.1		-5.6		36.5			11.4
% increase 22	7.8	7.4		7.6		4.3		3.4			3.9		3.4		3.6			3.5
% increase T3	30.6	69.7		46.1		5.8		49.4			23.2		17.9		44.3			28.5
	Uttar Pradesh
	Bareilly					Nainital							Saharanpur
	Paddy	Wheat			Total		Paddy		Wheat			Total		Paddy		Wheat			Total
Crop growth rate (1981-98)	3.09	3.07			3.06		2.50		2.77			2.60		3.19		2.05			2.69
Crop growth rate (1981-90)	6.63	2.42			4.81		3.87		2.58			3.44		4.77		3.80			4.32
Crop growth rate (1990-98)	2.36	3.91			3.02		-0.18		2.64			0.86		1.19		2.39			1.66
Mean (1981-83)	1.93	1.74			3.67		3.41		2.00			5.40		2.18		1.96			4.14
Mean (1988-90)	3.23	2.01			5.24		4.53		2.48			7.01		3.26		2.61			5.87
Mean (1990-92)	3.01	2.22			5.22		4.57		2.72			7.30		3.61		2.54			6.14
Mean (1996-98)	3.54	2.74			4.91		4.59		2.83			7.42		3.99		2.85			5.41
% increase 11	67.6	15.5			42.9		32.9		24.1			29.7		49.4		33.2			41.7
% increase 22	17.8	23.6			-6.0		0.3		4.0			1.7		10.5		12.2			10.9
% increase T3	83.7	56.3			33.9		34.7		41.8			37.3		82.8		44.0			64.4
	Uttar Pradesh
	Gorakpur					Faizabad							Varanasi
	Paddy	Wheat		Total		Paddy		Wheat			Total		Paddy		Wheat			Total
Crop growth rate (1981-98)	5.01	2.60		3.86		3.98		1.75			2.96		5.47		4.31			4.99
Crop growth rate (1981-90)	8.33	2.79		5.72		4.53		1.47			3.14		5.38		4.56			5.06
Crop growth rate (1990-98)	1.96	5.79		3.59		1.23		3.58			2.21		4.79		2.93			4.04
Mean (1981-83)	1.59	1.66		3.25		2.01		1.86			3.87		1.96		1.51			3.46
Mean (1988-90)	2.69	2.11		4.80		2.89		2.19			5.08		2.95		2.19			5.14
Mean (1990-92)	2.78	2.03		4.80		3.05		2.22			5.27		3.19		2.30			5.49
Mean (1996-98)	2.94	2.32		5.27		3.21		2.44			5.65		3.66		2.45			6.11
% increase 11	69.1	27.4		47.8		43.7		17.7			31.2		50.8		45.1			48.4
% increase 22	6.1	14.8		9.7		5.3		9.7			7.1		14.5		6.6			11.2
% increase T3	84.9	40.3		62.1		60.0		30.7			45.9		87.0		62.5			76.3
	Bihar
	Patna									Aurangabad
	Paddy		Wheat			Total				Paddy			Wheat				Total
Crop growth rate (1981-98)	1.90		2.98			2.51				4.31			6.15				5.12
Crop growth rate (1981-90)	5.44		4.19			4.91				5.15			4.48				4.86
Crop growth rate (1990-98)	5.44		3.39			4.38				12.87			9.48				11.15
Mean (1981-83)	1.75		1.57			3.32				1.95			1.39				3.34
Mean (1988-90)	2.80		2.15			4.95				2.25			1.56				3.80
Mean (1990-92)	2.13		2.10			4.23				1.99			1.64				3.63
Mean (1996-98)	2.65		2.38			5.04				3.09			2.20				5.29
% increase 11	59.5		36.8			48.7				15.5			11.7				13.9
% increase 22	24.9		13.5			19.2				55.2			34.4				45.8
% increase T3	51.3		51.7			51.5				58.9			57.9				58.5
	Bihar
	Bhojpur									Samastipur
	Paddy		Wheat			Total				Paddy			Wheat				Total
Crop growth rate (1981-98)	2.92		5.61			4.07				2.31			1.57				1.84
Crop growth rate (1981-90)	2.68		0.02			1.62				8.42			3.87				5.74
Crop growth rate (1990-98)	14.72		9.54			12.27				-4.16			3.37				0.06
Mean (1981-83)	2.48		1.68			4.16				0.94			1.56				2.50
Mean (1988-90)	2.67		1.66			4.33				1.71			2.12				3.83
Mean (1990-92)	2.15		2.04			4.19				1.50			1.76				3.26
Mean (1996-98)	3.46		2.73			6.19				1.35			2.04				3.39
% increase 11	7.6		-1.2			4.1				81.7			35.9				53.2
% increase 22	60.9		33.8			47.7				-9.9			15.7				3.9
% increase T3	39.6		62.2			48.7				43.8			30.4				35.4

¹% increase 1 = percentage increase of mean (1988-90) over mean (1981-83).

²% increase 2 = percentage increase of mean (1996-98) over mean (1990-92).

³% increase T = percentage increase of mean (1996-98) over mean (1981-83).

In Uttar Pradesh, the rice growth rate was moderate over the 18-year period, but decreased rapidly during the 1990s in all districts except Varanasi, in contrast to wheat, which registered increased growth (Table 8). The overall moderate growth of rice at state level in the 1990s should not mislead the state into remaining complacent, as it is expected that the growth rate in many of the major rice-growing districts, especially in the western region, will be alarmingly low. All districts, except Samastipur in Bihar, have shown impressively high growth (5.44-14.72 percent), which is either higher than, or comparable to, that of the 1980s (Table 7). There are three major reasons for this impressive growth:

• accelerated adoption of improved varieties, if not ideal high-yielding varieties for lowland ecologies;
• increased consumption of fertilizer nutrients;
• steadily expanding area under boro rice.

If this growth pattern is maintained, Bihar could soon be a major contributor to sustained yield growth at national level.

Overall analysis of growth trends across states and districts in the IGP suggests, with certain exceptions, a negative association between growth rate and yield level. The majority of the high productivity districts show relatively low growth rates (as in the trans-Gangetic zone) and low productivity districts register high growth rates (as in the central and eastern zones).

The study of system productivity revealed an upward trend (as observed in rice and wheat), with the pace varying according to the region. In the high-productivity upper Gangetic zone, the growth rate was quite low (<1.5 percent) in all districts except Jind, while it was fairly high (2.60-3.86 percent) in the medium-productivity zone (central part of Uttar Pradesh) and impressively high with a few exceptions in the low-productivity zone (eastern Uttar Pradesh and Bihar) (Table 7). The relative influence of rice or wheat or both on the growth rates achieved varied, depending on the region. In the upper Gangetic zone and the lower Gangetic plains (Bihar), rice and wheat had an equal influence; in eastern Uttar Pradesh rice was the major influence.

In the high-productivity areas with very low growth rates, the optimization and sustenance of yield by diagnosing and correcting yield-limiting factors should receive priority attention. If the constraint is found to be a genetic limitation of the currently cultivated varieties, then a variety with a higher yield threshold should be developed. The readily available hybrid technology and new plant varieties already being developed might help to raise the ceiling. Researchers and policy-makers are further concerned about the signs of declining yield in a few districts (for example Ludhiana) under the rice-wheat system. This should be viewed as an early warning of the need for serious research in high productivity areas.

Micro-level study

Data-sourcing for micro-level study from seed farms and progressive farmers has been a difficult experience. The use of data from large seed farms with highly reliable information on output/input was found to be a good alternative to structured experiments, which would take several years to generate such data. Analysis of the yield growth of rice and system productivity confined to the last seven to nine years revealed the trends to vary, depending on the region and the farm. The trend of very low positive to negative growth observed at most of the seed farms in the trans-Gangetic zone concurred with that observed at macro level (Tables 8 and 9). In the farmers' fields, the level of growth was relatively higher than in the seed farms. Unlike the component crop, wheat, which showed higher growth (5.4-10.8 percent), growth in rice was highly negative, especially in those with high yield average. Moderate-to-high growth observed in certain seed farms and farmers' fields could be taken as an indication that even within a district or subdistrict there could be pockets with scope for a sizeable yield increase. Farm-to-farm differences in the level of crop management by individual farmers could be the reason for instances of high growth. Excessive application of fertilizer (a common practice among farmers in this region) may have resulted in such economically non-sustainable growth.

The findings in Uttar Pradesh suggest that yield growth follows different trends. While in Tarai region (Pantnagar) rice showed positive growth compared to wheat (which registered negative growth), at Kanpur both the crops registered high positive yield growth, with rice contributing substantially to the system productivity, and at Varanasi farm both registered negative growth (Table 10). In Bihar, unlike the high positive growth of rice yields observed in the macro-level study, data from well-managed seed farms reveal a uniformly negative trend. This situation may be explained by the very high yield level (5-6 tonnes/ha) already achieved in these farms. The inference is that until state and district yield averages attain levels closer to those of the seed farms, immense scope remains for an appreciable rise in the productivity of rice at state level (Table 11).

TABLE 8

Yield growth (kg/ha) of rice, wheat and total productivity in selected seed farms and on-farm trials under the rice-wheat system in Punjab

		Seed farms
		PAU, Fathegarh Sahib			PAU, Ropar				KVK, Patiala
		Paddy	Wheat	Total	Paddy		Wheat	Total	Paddy			Wheat	Total
Crop growth rate	1.91		0.54	1.29	-10.70		1.81	-4.75	-0.16			3.72	1.26
Mean (91-93)	4 442		3 822	8 166	3 288		2 299	5 542	5 246			3 550	8 796
Mean (96-98)	4 838		4 241	8 882	1 841		2 780	4 241	5 006			4 510	9 516
% increase1	8.9		11.0	8.8	-44.0		20.9	-23.5	-4.6			27.0	8.18
	On-farm trials
		Dalanpur			Birdwal				Bakshiwala
		Paddy	Wheat	Total	Paddy		Wheat	Total	Paddy			Wheat	Total
Crop growth rate	7.8		10.8	9.1	-11.4		5.6	0.0	-4.4			5.4	0.0
Mean (96-98)	4 750		3 850	9 350	5 700		5 000	10 900	6 950			4 350	11 450
Mean (98-00)	5 450		4 750	10 200	4 850		5 500	10 350	6 500			4 750	11 250
% increase2	14.74		23.38	9.09	-14.91		10.00	-5.05	-6.47			9.20	-1.75

¹ Percentage increase of mean (1996-97 to 1997-98) over mean (1991-92 to 1992-93).

²Percentage increase of mean (1998-99 to 1999-2000) over mean (1996-97 to 1997-98).

TABLE 9

Yield growth (kg/ha) of rice, wheat and total productivity in selected 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			1.45	1.55		1.49		2.97		1.87	2.48		1.65		2.65	2.09		2.36		3.25		2.73
Mean (1993-95)			6 200	4 650		10 850		5 900		5 000	10 900		6 450		5 000	11 450		6 350		4 750		11 100
Mean (1997-99)			6 650	4 950		11 600		6 700		5 450	12 150		6 900		5 550	12 450		6 900		5 450		12 350
% increase1			7.26	6.45		6.91		13.56		9.00	11.47		6.98		11.00	8.73		8.66		14.74		11.26
			On-farm trials													Seed farm
			Rasulpur 4, Karnal						Sikanderpur, Sirsa							DWR, Karnal
	Paddy				Wheat		Total		Paddy			Wheat		Total		Paddy			Wheat		Total
Crop growth rate	-4.44				1.02		-1.90		-2.94			2.47		-0.36		7.22			2.84		4.91
Mean (1993-95)	6 350				5 125		11 475		5 500			3 750		9 250		4 600			4 450		9 050
Mean (1997-99)	5 300				5 300		10 600		4 750			4 750		9 500		5 349			4 978		10 327
% increase1	-16.54						-7.63		-13.64			-13.64		2.70		16.27			11.87		14.10

¹Percentage increase of mean (1997-98 to 1998-99) over mean (1993-94 to 1994-95).

TABLE 10

Yield growth (q/ha)1 of rice, wheat and total productivity in selected 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	28.89	38.84	67.72	43.68	42.50	86.18
Mean (1998-2000)	44.54		28.42	72.96	53.13	43.65	96.78	35.33	34.38	69.70
% increase2	-1.03		10.05	3.01	83.92	12.40	42.90	-19.12	-19.12	-19.12

¹ 1 q = 100 kg.

²Percentage increase of mean (1998-99 to 1999-2000) over mean (1991-92 to 1992-93).

TABLE 11

Yield growth (kg/ha) of rice, wheat and total productivity in seed and on-farm trials under the rice-wheat system in Bihar

	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	-2.68	-1.26		-12.86	-4.77	-0.23	-12.15	-5.28	-7.34		-2.08	-5.38
Mean (1992-94)	5 174		3 025	8 199	6 218		4 830	10 145	4 909	4 222	9 130	5 287		2 800	8 087
Mean (1997-99)	4 855		2 136	6 991	5 280		2 032	7 311	4 399	2 244	6 643	3 273		2 348	5 620
% increase1	-6.16		-29.40	-14.73	-15.09		-57.94	-27.93	-10.39	-46.84	-27.25	-38.10		-16.16	-30.50

	Seed farms													On-farm trials
	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	-14.80	1.38		-11.00	-3.49	-4.48		-17.19	-12.93		8.75		4.99	7.41
Mean (1992-94)	5 845		4 700	10 545	4 748		4 148	8 896	5 858		4 874	10 732		3 400		1 963	5 425
Mean (1997-99)	4 724		2 254	4 616	4 857		2 500	7 356	4 268		2 002	5 269		4 960		2 400	7 360
% increase1	-19.18		-52.04	-56.23	2.29		-39.73	-17.31	-27.14		-58.92	-50.90		45.88		22.29	35.67

¹Percentage increase of mean (1997-98 to 1998-1999) over mean (1992-93 to 1993-94).

Long-term experimental trials

Reports of nutrient imbalances and depletion due to the heavy withdrawal of crops - more so in intensively cultivated high-productivity regions - have been instrumental in experiments focusing on systematic and continuous monitoring of growth trends; strengthening of long-term nutrient dynamics in the soil-plant system; and sustainability of the two rice-based cropping systems. In the present study, data already being generated by such long-term experiments by various national and international organizations have been compared with the observations of the macro- and micro-level studies. Data from long-term experiments at Ludhiana, Karnal and Pantnagar, repre-senting the high-productivity northwestern region, indicated a significant decline in the growth trends of rice at recommended levels of fertilizer application. This finding confirmed the trend observed by the macro- and micro-level studies. In contrast, the growth trends of wheat were found to fluctuate (Table 12). The decline of rice yields in the Tarai Region has been attributed to zinc deficiency and a loss of native soil fertility in terms of organic carbon content and available NPK (Nambiar, 1995). A similar decline observed at the Ludhiana centre has been associated with a decreasing nitrogen supply capacity of the soil and a depletion of sulphur (Yadav, Dwivedi and Pandey, 2000).

TABLE 12

Trends in grain yields of rice and wheat in long-term experiments at recommended fertilizer application in the northwestern Gangetic plains

	Ludhiana (1988-1996)		Karnal (1976-1996)		Pantnagar (1984-1998)		Pantnagar (1978-1998)
	Initial	Final	Initial	Final	Initial	Final	Initial	Final
Rice yield (tonnes/ha)	6.32	5.47	6.69	6.10	7.17	5.50	4.15	4.25
Wheat yield (tonnes/ha)	4.32	4.25	4.45	4.73	3.68	3.05	3.00	3.90
% change (rice)	-13.4		-8.8		-23.3		+2.4
Slope (rice)	0.212 tonnes/ha		-		-2.33%		+0.76%
% change (wheat)	-1.6		+6.3		-17.1		+30.0
Slope (wheat)	-0.017 tonnes/ha		-		-1.95%		+2.4%

In the mid and lower Gangetic plains covering central and eastern Uttar Pradesh and Bihar, rice yields were again found to be declining along with wheat yields, but at a relatively slower pace, while in the lower Gangetic plains they were declining at a much higher rate (Table 13). For rice, these findings again broadly concur with the observations of the macro- and micro-level studies (except at Kanpur) in the 1990s; in the case of wheat the findings differ. In the majority of locations, the decline in the productivity of rice was found to be associated with negative balances for potassium and location-specific loss of organic carbon and available NPK (Table 14).

Reviewing the results of 18 long-term experiments conducted across the IGP, Duxbury et al. (2000) summarized that rice productivity declined by 0.05 to 0.5 tonnes/ha/year in the majority of the experiments, while wheat yields either remained static or increased with time and the productivity trend of the system was dominated by the rice yield trend. Although organic manuring is said to improve the yield potential and slow down the pace of decline in rice productivity, there is very little evidence to this effect.

TABLE 13

Yield trends (kg/ha) of rice and wheat in long-term experiments under the rice-wheat system in the central and eastern Indo-Gangetic plains

	(1984-1997) Kanpur		(1984-1997) Faizabad		(1985-1997) Varanasi		(1977-1993) Sabour		(1986-1997) Kalyani		(1973-1997) Barackpore
	Initial	Final	Initial	Final	Initial	Final	Initial	Final	Initial	Final	Initial	Final
Rice	3 970	5 799	3 938	4 473	3 793	4 557	4 300	1 740	3 706	3 023	5 175	3 746
Wheat	4 685	4 539	3 965	4 082	3 738	3 975	2 980	1 740	2 748	2 768	2 675	2 340
% change (rice)		+46.1		+13.6		+20.1		-59.5		-18.4		-27.6
Slope (rice) (kg/year)		+153		+44		+109		-		-111		-79
% change (wheat)		-3.1		+3.0		+6.3		-41.6		-0.7		-12.5
Slope (wheat) (kg/year)		-4		+87		+5.4		-		-7		-6.7

TABLE 14

Changes (%) in soil fertility characteristics under the rice-wheat system in the northeastern Gangetic plains

Location	OC	N	P2O5	K2O
Kanpur	+44	-	+79	-16
Faizabad	+19	+13	+51	-20
Sabour	-49	-13	-23	-28
Kalyani	-35	+47	-7	+72
Barackpore	-27	-	+86	+34