Effect of direct seeded rice based intercropping system and source of organic inputs on nutrient uptake of crops and soil properties under rainfed condition

Introduction

Rice (Oryza sativa L.) is a premium food grain crop and is often the main source of calories and the principal food of millions of people. It has been referred as "Global Grain" because of its use as a prime staple food in about 100 countries of the world and provides staple food to more than half of the world's population. Asia is considered to be 'rice bowl' of the world and it produces and consumes more than 90 per cent of the world rice (Tyagi et al., 2004). India ranks first in area and second in production. It also plays a pivotal role in Indian agriculture, is also considered as a major staple food for more than 70% Indian population. It is grown in all states and in all ecologies. Aerobic rice involves sowing dry seed into a prepared seedbed. In India, direct seeded aerobic rice production systems are rapidly replacing conventional rice production systems due to several advantages. In India, rice covers the largest area of about 43.78 million hectares and producing 118.43 million tons with a productivity of 2705 kg/ha and extensively grown in most of states (Anonymous, 2020) [1] . West Bengal is the highest rice producing state in India followed by Utter Pradesh, Andhra Pradesh, Punjab, Tamil Nadu, Bihar, Chhattisgarh, Odisha, Assam, Karnataka and Gujarat. In Gujarat, most of the area under rice crop is confined in middle to south Gujarat about 9.06 lakh hectares area with the production of 21.47 lakh tons and productivity of 3269.7 kg/ha comprising the districts of Ahmedabad, Kheda, Anand, Vadodara, Dahod, Panchmahals, Surat, Valsad, Tapi, Dang and Navsari (Anonymous, 2021) [2] . Among the different sources of organic matter, farmyard manure (FYM) is considered the most important for organic farming particularly in India because it is readily available on most farms, cost-effective, and well-suited to smallholder conditions where livestock and crop production are integrated. FYM provides a continuous and balanced supply of nutrients, improves soil structure and water holding capacity, and supports microbial activity, making it a reliable input for sustaining soil fertility under diverse Indian agro-climatic conditions. (Rajan et al., 2023) [11] . Jivamrit has gained prominence in organic and natural farming in India because it not only supplies nutrients but also acts as a powerful microbial inoculant that accelerates the decomposition of organic matter and enhances soil biological activity. Intercropping means growing of two or more than two crops simultaneously on the same piece of land with specific planting geometry or in separate rows. The commonly used legumes for intercropping include Groundnut, Soybean, Green gram, Black gram, Pigeonpea, Cowpea, Clusterbean, etc. The potential of growing legumes in association with major staple food crops like rain fed rice could be substantially enhanced through intercropping. This will help to improve and maintain fertility of soil, ensuring efficient utilization of nutrients and to ensure economic utilization of land and capital (Jeyabal et al., 2001) [4] . It also allows efficient utilization of nutrients and ensuring economic utilization of land, labour and capital (Maingi et al., 2001) [6] .

Materials and Methods

A field experiment was conducted at Regional Rice Research Station, Navsari Agricultural University, Vyara, Dist. Tapi (Gujarat) during the kharif seasons of 2023 and 2024, entitled with "Effect of direct seeded rice based intercropping system and source of organic inputs on nutrient uptake of crops and soil properties under rainfed condition". Fourteen treatments comprising source of organic input along with intercropping systems viz., F1I1: (100% RDN through FYM) + (rice sole crop), F 1 I 2: (100% RDN through FYM) + (black gram sole crop), F 1 I 3: (100% RDN through FYM) + (soybean sole crop), F 1 I 4: (100% RDN through FYM) + (groundnut sole crop), F 1 I 5: (100% RDN through FYM) + (4:1 rice + blackgram), F 1 I 6: (100% RDN through FYM) + (4:1 rice + soybean), F 1 I 7: (100% RDN through FYM) + (4:1 rice + groundnut), F 2 I 1: (50% RDN through FYM + 500 l/ha jivamrut) + (rice sole crop), F 2 I 2: (50% RDN through FYM + 500 l/ha jivamrut) + (black gram sole crop), F 2 I 3: (50% RDN through FYM + 500 l/ha jivamrut) + (soybean sole crop), F 2 I 4: (50% RDN through FYM + 500 l/ha jivamrut) + (groundnut sole crop), F 2 I 5: (50% RDN through FYM + 500 l/ha jivamrut) + (4:1 rice + blackgram), F 2 I 6: (50% RDN through FYM + 500 l/ha jivamrut) + (4:1 rice + soybean), F 2 I 7: (50% RDN through FYM + 500 l/ha jivamrut) + (4:1 rice + groundnut) were evaluated in randomized block design with factorial concept replicated thrice. The experimental field was prepared by tractor ploughing followed by harrowing and planking to obtain a fine tilth. Furrows were opened and plots were laid out as per the experimental plan. Well-decomposed farmyard manure (FYM), derived from Surti buffalo, was applied 10-15 days before sowing according to the treatments and incorporated into the soil during bed preparation. The recommended dose of nitrogen was supplied through FYM on an equivalent nitrogen basis as per the recommended dose for rice. Jivamrut was applied as a drenching in soil at the time of sowing, 30 DAS and 60 DAS at a rate of 500 l/ha each, as per treatment combinations. Recommended spacing of 30 cm for rice and 30 × 10 cm for black gram, soybean, and groundnut was maintained. The rice variety GR-16 (Tapi) and the intercrops black gram (GU-3), soybean (KDS-344), and groundnut (GG-34) were sown at seed rates of 50, 15, 60, and 120 kg/ha, respectively. Seeds were sown in previously opened furrows at a depth of 5-6 cm and properly covered with soil. The plant samples were analyzed for N, P and K content as per the standard methods. The concentration of nutrients in seed and stover were used to calculate the uptake of nutrients by rice and intercrops. The soil samples were collected from each net plot after harvest of groundnut crop at 0-15 cm depth. Organic carbon, available N and P2O5 and K 2 O status of soil were analyzed by Walkely and Black's method, Alkaline KMnO 4 method, Olsen's method and Flame photometric method, respectively. The data were statistically analyzed for various characters as described by (Panse and Sukhatme, 1985) [14] experimentation and in pooled study.

Results and Discussion

Nutrient content and uptake (N, P and K) by rice grain and straw

The different sources of organic inputs did not exert any significant influence on the N, P and K content in rice grain and straw. Similarly, nutrient uptake by rice grain and straw (N, P and K) was also unaffected by organic input treatments. The rice based intercropping systems had no significant impact on NPK content in both rice grain and straw. In terms of nutrient uptake, nitrogen uptake by rice grain was not significantly influenced by intercropping systems. However, phosphorus and potassium uptake by rice grain were significantly higher in the I1: sole rice crop. For rice straw, N, P and K uptake were significantly higher under I 1 , where in case of N uptake by straw, I 6: Rice + soybean (4:1) remained at par with I1. The interaction between sources of organic inputs and intercropping systems did not show any significant influence on the NPK content in grain or straw nor on nutrient uptake by rice grain and straw.

Total nutrient uptake (N, P and K) by rice

Sources of organic inputs did not significantly affect on total nutrient uptake of rice. Among intercropping systems, I 1: sole rice recorded the significantly highest total N and total P uptake of rice. Rice showed the lowest nutrient uptake when intercropped with blackgram. Potassium uptake was significantly higher under I 1: sole rice in 2024 and pooled analysis but showed no significant difference in 2023. The interaction effect between sources of organic inputs and intercropping systems were not significant for total N, P or K uptake across the years and pooled analysis. The higher nutrient uptake in grain, straw and total uptake by rice under I 1: sole rice can be attributed to its higher plant population per unit area, which provides a greater sink size and higher nutrient demand and ultimately leading to increased uptake of N, P and K. This advantage of cereals in sole stands over intercrops is primarily due to greater root density and competitive ability for available resources (Jabbar et al). The beneficial effect observed with I 6: rice + soybean being statistically comparable to sole rice in N uptake may be due to the superior biological nitrogen fixation capacity of soybean and its partial transfer of nitrogen to rice in the intercropping system, as supported by Meena et al. (2018) [7] and Peoples et al. (2021) [10] .

Total nutrient uptake (N, P and K) by rice based intercropping system Effect of source of organic inputs: Among the sources of organic inputs, significantly higher total N and K uptake by intercropping system was recorded under F 1: 100% RDN through FYM, whereas P uptake also showed non-significant result. This superiority of F 1 over F 2 can be attributed to the fact that FYM supplies a larger and more balanced quantity of primary nutrients directly to the soil, ensuring sustained availability of N, P and K throughout the crop growth period. The higher nutrient input from FYM also improves soil organic matter, microbial activity and cation exchange capacity, which in turn enhances nutrient mineralization and uptake efficiency of the crop. These results are consistent with Kusnarta et al. (2021) [5] , Choudhary et al. (2022) [3] and Urmi et al. (2022) [13] Effect of intercropping systems Regarding intercropping systems, the highest total N uptake was observed in I 3: sole soybean, while the lowest was recorded in I 2: sole blackgram. A similar trend was noted for phosphorus uptake, with I 3 showing the highest values, statistically at par with I 4: sole groundnut and I 2 recording the lowest values. Discussing the overall nutrient dynamics of the intercropping system, the significantly higher total N and P uptake observed in I 3: soybean sole crop and I 4: groundnut sole crop can be attributed to their strong nitrogen fixing ability and greater biomass production compared to blackgram. Legumes establish symbiotic associations with rhizobium bacteria which fix atmospheric nitrogen into plant available forms and enrich both the host plant and the rhizosphere. Soybean is documented to fix the maximum amount of atmospheric nitrogen followed by groundnut, while blackgram contributes the least. This higher nitrogen input enhances vegetative growth, dry matter accumulation and root activity thereby improving the uptake of phosphorus and other nutrients. In case of potassium uptake, I7: rice + groundnut recorded the significantly higher values, at par with I 6: rice + soybean and I1: sole rice, whereas I 2 again recorded the lowest uptake. The higher total K uptake under I 7: rice + groundnut, which was at par with I 6: rice + soybean and I 1: sole rice, may be attributed to root complementarity and efficient nutrient use in rice legume systems. Groundnut exploits deeper soil layers, while rice utilizes surface nutrients. Moreover, rice has a higher K uptake capacity, which contributes substantially to total system K uptake. Peoples et al. (2021) [10] , Choudhary et al. (2022) [3] , Mohan et al. (2023) [8] and Palmo et al. (2024) [9] also supported the present findings.

Interaction effect

The Interaction effect between sources of organic inputs and intercropping systems was found to be non-significant for total uptake of N, P and K across both years and in the pooled analysis.

Soil fertility status

The results about soil pH, electrical conductivity and organic carbon as well as available nitrogen, phosphorus and potassium showed that none of these soil parameters were significantly influenced by the sources of organic inputs, rice based intercropping systems and their Interaction effect.

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