Preceding Rainy-Season Crops and Residue Management Practices on Growth, Yield and Economics of Succeeding Wheat under Zero-till Semi-Arid Condition

Conservation agriculture involving zero-till residue management practices with crop diversity of short-duration rainy-season crops may be more viable approach to increase the productivity and resource-use efficiency in semi-arid dryland areas. To identify suitable wheat-based cropping system an experiment was conducted with three preceding rainy-season crops pearlmillet, clusterbean and greengram along with crop residue and Leucaena twigs mulching. Both rainyand winter-season crops were grown under zero-till along with other recommended package of practices under rainfed conditions during 2010-11 and 2011-12. Grain yield of wheat was significantly higher in 2011-12 than in 2010-11, and with crop residue than no residue. Preceding greengram resulted in significantly higher grain yield of wheat (1.11 t ha-1 in 2010-11, and 2.49 t ha-1 in 201112), followed by that after clusterbean. Greengram with crop residue recorded the highest grain yield of wheat (3.32 t ha-1), followed by clusterbean with Leucaena twigs (3.29 t ha-1) and clusterbean with crop residue (2.94 t ha-1) in 2011-12. The nutrient uptake followed the same trend as grain and straw yield. The magnitude of total nutrient uptake of wheat was about 25% more in 2011-12, than in 2010-11 due to its higher biomass production in latter year. The economic analysis exhibited the highest returns after greengram with crop residues and clusterbean with Leucaena twigs. It was concluded that wheat after greengram and clusterbean with crop residue and Leucaena twigs mulching provided higher productivity and profitability under semi-arid zero-till condition.


Introduction
In rainfed areas of semi-arid region, wheat is normally grown during winter after short-duration, drought-hardy diverse rainyseason crops of cereals (pearlmillet) and legumes (clusterbean and greengram). The average growth and productivity of wheat in rainfed dry lands are less than half as that of irrigated ecosystem [1]. System-oriented production technology is essential in dry land areas for maximizing the land productivity by harnessing synergies generated through various interactions in soil-crop-atmosphere continuum. Inclusion of legumes and oilseeds in the cerealbased system of these lands not only utilizes the soil nutrients and residual moisture, but also minimizes the pest hazards, and provides balanced components of proteins and fatty acids to the human beings [2]. Moreover, the inclusion of legumes in the dry land cropping system plays a vital role in improving soil fertility through addition of biologically fixed N 2 [3].
Conservation tillage practices (zero-tillage + mulching + crop diversification) are a viable approach to conserve soil moisture and nutrients under dry land situations. Use of organic materials as mulch is considered poor conductor of heat that effectively moderate soil temperature, maintain soil moisture, and increase soil fertility [4] under rainfed agriculture. Several evidences of remarkable crop yields increment in maize-wheat system through the maintenance of appropriate vegetative cover have been documented [5][6][7][8].
Prunings of Leuceana twigs as mulch are effective for both rainy and winter-season crops [7,9]. with significant residual effects on soil fertility and productivity of subsequent crops [10,11]. Adoption of resource-conserving technologies involving zero-tillage and organic residue management is the need of the hour as a method of 'low-input agriculture' to improve productivity, resource-use efficiency and achieve sustainability in rainfed ecosystem [12]. A considerable amount of research work on conservation agriculture have been done in India and south Asia under irrigated ecosystem, but scanty information is available particularly in semi-arid drylands. Therefore, the present research work was undertaken to explore the feasibility of double cropped wheat-based system through zero-tillage and residue management under rainfed condition.

Materials and Methods
A field experiment was conducted at the Indian Agricultural Research Institute, New Delhi (28 0 40'N, 77 0 12'E, 228 masl.) during 2010-11 and 2011-12 to study the effect of residue management and preceding rainy-season crops on growth, productivity, nutrient uptake and economics of wheat-based cropping systems. The daily meteorological data showed that there was high rainfall (954 mm) in 2010, while it was 30.6%, less than that of 2010 in 2011 (662 mm) and 10.4% less than that of average of 10 years (739 mm).
There were more rains (10 rainy days, 85 mm) during the crop season of wheat (October to April) in 2010-11, but rains were negligible (3 rainy days, 34 mm) in 2011-12.
The soil of the experimental field was sandy-loam in texture, with 147.2 kg ha -1 alkaline KMnO 4 -oxidizable N, 17.0 kg ha -1 NaHCO 3 -extractable P, 225.1 kg ha -1 1N NH 4 OAc-exchangeable K, 0.40% organic C with 7.5 pH of soil reaction (1: 2.5 soil and water ratio). The moisture content at -1/3 and -15 atmospheric tensions was 18.8 and 6.5%, respectively, with bulk density 1.55 Mg m -3 of surface soil layer (0-15 cm). Nine cropping systems involving combinations of three crops each in rainy season (pearlmillet, clusterbean and greengram) and winter season (wheat, chickpea and mustard) were grown in sequence, exclusively under zerotill rainfed condition following other recommended package of practices. Three treatments of surface cover management, viz.
control (no-residue), crop residues @ 5 t ha -1 and Leucaena twigs @ 10 t ha -1 green biomass were maintained in both the seasons.
The experiment was laid out in Randomized Block Design with four replications. Only three wheat-based systems out of nine diverse systems from the whole study is presented here in this research. weight and 1000-grain weight were taken from randomly selected ten wheat spikes. The grain and stover yields were recorded from the net plot of 10 m 2 area, and grain yield was adjusted at 14% moisture. The concentration of N, P and K in grain and straw of wheat was analyzed as per the standard methods [13]. and the uptake values were calculated on the basis of their dry matter yield at harvest. Economic analysis was done, and expressed as cost of cultivation, gross and net returns and net returns/` invested. The biometric data on ancillary and yield parameters were analyzed by standard statistical techniques and regression analysis for major yield attributes and grain yield was done [14].

Soil moisture pattern and crop growth indices
The crop residues held more soil moisture than the Leucaena twigs and no-residue, which resulted in higher crop growth rate under residue retention ( Figure 1). The available rainfall was conserved by crop residues, which showed higher crop growth rate. Wheat is a moisture-sensitive crop, and the growth and development depend on brighter sunshine hours and favourable soil moisture.
Crop growth rate (CGR), relative growth rate (RGR), and net assimilation rate (NAR) showed that higher rates of these parameters were recorded under crop residue mulching and from 30-60 DAS (Table 1 &

Regression and co-relations of yield and yield attributes
Regression analysis between yield and yield attributes of wheat exhibited significant positive correlation between wheat yield (y) with major yield attributes (x), viz. effective tillers m -2 and number of filled grains during both years, but 1000-grain weight remained significant only in 2010-11 ( Figure 2).

Yield performance
Grain, straw and biological yields of wheat showed significant variation due to preceding crops and residue management practices Preceding greengram along with crop residue recorded significantly higher grain yield (3.32 t ha -1 ), followed by clusterbean both with Leucaena twigs (3.29 t ha -1 ), and with crop residue (2.94 t ha -1 ) in 2011-12. However, these values remained non-significant in 2010-11. In 2011-12, retention of crop residue showed significantly superior grain yield over no residue and Leucaena twigs. These variations could be attributed to higher availability of nutrients and soil moisture provided by crop residue application. Crop residue resulted in conservation of soil moisture, and this resulted in higher yield over control and Leucaena twigs mulching. Clusterbean-wheat system produced the highest yield at Hisar [18]. and maximum water-use efficiency at Gwalior (Singh et al. (1998)). However, greengram-wheat and pearlmillet-wheat cropping systems were found suitable in Rajasthan [19,20].
Pooled analysis of grain yield of wheat as affected by year, preceding crops and residue management practices are presented in (Table 3).  Although there was less rainfall in the second year, the grain yield was 103% higher (2.03 t ha -1 ) than in the first year (1.0 t ha -1 ).

Year (A) Preceding crop (B) Residue (C) A x B A x C B x C A x B x C
In  Data on nutrient uptake by wheat are shown in (Table 4 & 5).

Nutrient uptake
In general, the pattern of grain yield and straw yield was followed in total nutrient uptake as well. The rainy-season crops showed significant variation in N, P and K uptake by wheat grain and straw.
Greengram resulted in significantly higher grain and straw yield, and hence the nutrient uptake due to the better crop performance with crop residue retention. Similarly, crop residue management also showed significant variation in nutrient uptake with the maximum uptake under crop residue treatment. The magnitude of total nutrient uptake by wheat in 2011-12 was about 50% more than in 2010-11 due to its higher productivity. Interaction revealed that the highest values for N and P uptake in grain after greengram and clusterbean and K uptake after pearlmillet as preceding crops.
Significantly higher nutrient uptake with crop residue and Lecuaena twigs was due to higher growth parameters, resulting in better and higher yield over the control. There was poor crop growth in no-residue treatment; and therefore, nutrient uptake was also less in control than with residue application. The increased uptake of NPK under residue application was attributed to higher yield because of availability of moisture to the plants. The overall improvement in growth of wheat due to residual effect of crop residue applied to previous legumes like greengram and clusterbean, and with Leucaena twigs could be ascribed to their pivotal role in several physiological and biochemical processes, viz. root development, photosynthesis, energy transformation (ATP and ADP) and symbiotic biological N 2 fixation processes and in protein synthesis [3,16,21].

Economics
The perusal of data on economic performance of wheat as influenced by preceding rainy-season crops and residue management suggested that cost of cultivation was relatively high in 2011-12 than 2010-11, but the net returns were almost half in 2010-11 compared with 2011-12 ( Table 6). The increase in production cost in 2011-12 was due to higher labour wages by 33% and other input costs. There was higher yield in 2011-12 and value of output was also high, resulting in 50% more net returns. This indicated that wheat after greengram and clusterbean along with crop residue and Leucaena twigs mulching was high-yielding and profitable cropping system under zero-till semi-arid condition.

Conclusion
It was concluded that growth parameters, yield attributes, yield, nutrient uptake and economics of wheat was significantly influenced by preceding rainy-season crops and residue retention.
Crop residue retention followed by Leucaena twigs was found to be significantly better than no-residue. It was recommended to adopt greengram-wheat and clusterbean-wheat cropping systems with crop residue or Leucaena twigs under zero-till semi-arid condition.