Custard Apple Soil Health Management: Building Fertility for Long-Term Orchard Productivity

Long-term soil monitoring research spanning 18 years conducted by ICAR-NRC for Arid Horticulture and Mahatma Phule Krishi Vidyapeeth Rahuri across commercial custard apple orchards in Nashik, Aurangabad, and Solapur districts of Maharashtra documents a clear divergence in productivity trajectories between orchards managed with integrated soil health approaches and those relying exclusively on synthetic fertiliser inputs. Orchards receiving annual organic matter additions, leguminous cover cropping, and balanced macro and micronutrient management maintained soil organic carbon above 0.8 percent and produced commercially viable yields of 60 to 80 kg per tree beyond 25 years of age. In contrast, orchards managed with only synthetic fertilisers and no organic matter addition showed progressive soil organic carbon decline to below 0.3 percent, increased soil compaction, rising incidence of soil-borne root diseases, and yield decline beginning at 12 to 15 years of orchard age. Building and maintaining soil health is therefore not simply an agronomic recommendation but the fundamental determinant of long-term custard apple orchard economic viability.

Understanding Custard Apple Root System and Soil Requirements

Root mapping research from IIHR Bangalore using trench excavation and minirhizotron techniques documents the spatial distribution of custard apple root systems and their implications for soil management. Custard apple develops a moderately deep taproot extending 1.5 to 2 metres into the soil profile combined with a dense network of lateral feeder roots concentrated in the top 30 to 45 cm of soil within a radius of 1 to 1.5 metres from the trunk. The feeder root zone in the top 30 cm is responsible for 70 to 80 percent of water and nutrient absorption and is therefore the most critical soil layer for management. IIHR research documents that soil bulk density above 1.55 g per cubic centimetre in this feeder root zone, commonly caused by repeated tillage and absence of organic matter, severely restricts root extension and reduces effective rooting volume by 30 to 40 percent. Maintaining soil bulk density below 1.4 g per cubic centimetre through organic matter addition and minimum tillage is the primary soil physical health target for custard apple orchard management.

Organic Matter Management: The Foundation of Soil Health

ICAR-NRCAH long-term fertility research quantifies the organic matter inputs required to maintain or build soil organic carbon in custard apple orchards on the shallow to medium-depth soils common in dryland Maharashtra and Andhra Pradesh. Annual application of 20 to 25 kg of well-decomposed farmyard manure or 8 to 10 kg of vermicompost per tree maintains soil organic carbon at existing levels in soils with initial organic carbon of 0.5 to 0.8 percent. To actively build organic carbon from degraded levels below 0.4 percent toward the target of 0.8 percent requires doubling organic matter application to 40 to 50 kg farmyard manure per tree per year for a minimum of 3 consecutive years, after which maintenance rates are sufficient. ICAR research confirms that incorporating green manure crops such as dhaincha or sunhemp in the inter-row spaces during the June to August monsoon period and incorporating the biomass into the soil before it sets seed adds 8 to 12 tonnes of fresh biomass per hectare equivalent to approximately 15 to 20 kg of additional farmyard manure per tree in terms of organic matter contribution, significantly reducing the quantity of external organic matter that must be purchased and transported to the orchard.

Cover Cropping for Soil Biology and Weed Management

Research from CRIDA Hyderabad on cover cropping in dryland fruit orchards documents that maintaining a permanent or seasonal cover crop in custard apple inter-row spaces provides multiple simultaneous soil health benefits that cannot be achieved through fertiliser inputs alone. Leguminous cover crops including stylosanthes, dolichos, and cowpea maintained as permanent or seasonal ground cover fix atmospheric nitrogen, maintain surface soil moisture through canopy transpiration reduction, prevent erosion on sloped orchard land, and sustain diverse soil microbial communities including mycorrhizal fungi that colonise custard apple roots and significantly improve phosphorus uptake efficiency. Mycorrhizal colonisation research published by Anand Agricultural University found that custard apple roots in soils with active mycorrhizal communities showed phosphorus uptake efficiency 40 to 60 percent higher than roots in soils where repeated fungicide and herbicide applications had suppressed mycorrhizal populations, meaning healthy soil biology directly reduces the quantity of phosphorus fertiliser required for the same yield response. Cover crop biomass mowed and left as surface mulch rather than incorporated adds 3 to 5 cm of organic mulch layer that maintains soil moisture and moderates soil temperature fluctuations across seasons.

Soil Testing and Targeted Fertiliser Management

Research from the National Bureau of Soil Survey and Land Use Planning Nagpur documents high spatial variability in soil nutrient status across custard apple growing districts of Maharashtra, Andhra Pradesh, and Madhya Pradesh, making blanket fertiliser recommendations less effective than soil-test-based targeted applications. Soil sampling and testing conducted through the nearest Soil Testing Laboratory of the state agriculture department or Krishi Vigyan Kendra costs only ₹200 to ₹500 per sample and provides pH, organic carbon, available nitrogen, phosphorus, potassium, sulphur, and micronutrient status data that allows precise identification of which nutrients are actually deficient versus which are already adequate in a specific orchard. ICAR research comparing soil-test-based versus blanket fertiliser application in custard apple orchards across Maharashtra found that farmers using soil-test recommendations applied on average 25 percent less total fertiliser while achieving 10 to 15 percent higher yields compared to farmers applying blanket recommended doses, because blanket doses frequently over-apply nutrients already adequate in the soil while under-applying those that are actually limiting yield. Soil testing every two years is the recommended frequency for mature custard apple orchards according to ICAR guidelines.

Managing Soil pH for Nutrient Availability

Soil pH management research specific to custard apple from Anand Agricultural University and MPKV Rahuri documents that the crop grows across a relatively wide pH range of 6.0 to 7.8 but achieves maximum nutrient availability and yield at pH 6.5 to 7.0. Soils below pH 6.0, found in some tribal and forest fringe areas where custard apple is traditionally cultivated, show aluminium and manganese toxicity symptoms in custard apple including stunted growth and interveinal leaf chlorosis that are frequently misdiagnosed as micronutrient deficiency. Liming with agricultural lime at 500 grams to 2 kg per tree depending on soil acidity severity corrects pH and eliminates toxicity symptoms within one growing season. Highly alkaline soils above pH 7.8, common in black cotton soil regions of Marathwada, cause iron, zinc, and manganese deficiency through precipitation of these micronutrients into unavailable forms. Acidification using elemental sulphur at 250 to 500 grams per tree incorporated into the root zone in May, or regular application of acidifying fertilisers such as ammonium sulphate instead of urea as the nitrogen source, progressively lowers pH in alkaline soils over 2 to 3 seasons and restores micronutrient availability without requiring expensive chelated micronutrient foliar sprays.