Livestock / Cropland Ratio

The livestock cropland ratio refers to the number of Tropical Livestock Units kept and the number of ha of cropland under cultivation based on the amount of manure that can be applied and the amount required to maintain soil fertility of cropland.

The quantity of manure produced is by definition equivalent to (100% - digestibility) times feed intake. In general, feed intake is lower when digestibility is lower. Consequently the amount of manure produced varies less than feed intake or livestock production.

The annual manure production of one Tropical Livestock Unit (250 kg live weight) in an extensive system is estimated at about 1,000 kg DM. This estimate is based on the assumptions of a daily feed intake varying from 2 – 2.5 % of body weight and a digestibility of feed varying from 40 – 60%.

Manure production is relatively constant while requirements for crop cultivation are seasonal. Manure has to be stored and storage losses occur. In general not all the manure produced is stored. Some is deposited on pastures while grazing and on the way from and to the kraal or stable. In many systems animals are not even on the farm during certain periods of the year: e.g transhumance. Consequently only a fraction of the manure produced is available for crop cultivation at the right time. Improved manure management can reduce losses. Adding litter and feed residues to manure in kraal, stable or manure pit will increase the quantity.

Manure requirements also vary depending on soil characteristics, ecological conditions and species of crop cultivated.

Estimates of, the amount of applicable manure per TLU and the manure requirements per ha for each sub system as presented in the Table. In practice they will also vary largely depending on management practices and ecological conditions. The assumptions on which the values are based show some principal factors that can be responsible for the variation within systems.

Estimates (Kg DM) of manure production, stored, lost and required on different sub-systems

Mixed sub system | Manure/ TLU | Litter & residues added | Manure collected on farm | Annual storage loss | Manure requir. per ha | TLU / ha
Communal grazing | 1,000 |  | < 500 | < 250 | 1,000 | 4
Crop residues | 1,000 | + 100 | + 750 | + 375 | 1,200 | 3 – 4
Cut and carry | 1,000 | + 200 | + 1200 | + 600 | 1,200 | 2
Feed from farm | 1,000 | + 200 | + 1200 | + 600 | 1,200 | 2
External feed | 1,200 | + 100 | + 1300 | + 650 | 1,000 | 1,5 - 2

Assumptions:

> Manure produced per TLU:
> In the sub systems with external feed an extra 200 kg DM is produced because of higher production level and thus a higher feed intake and manure production;

> Litter and crop residues added:
> In the crop residue sub system (mainly residues) and in the external feed sub system (litter and residues) an extra100 Kg DM per TLU is added to the manure produced in the cut and carry sub system (mainly residues) and in the feed from farm sub system (residues and litter), an extra 200 kg DM per TLU is added to the manure produced

> Manure collected on farm:
> In communal grazing subsystem animals produce half or less of their manure in kraal. In crop residues sub system animals produce about &frac34; of their manure in kraal. In the other sub systems animals produce all their manure in stable or kraal.

> Storage losses:
> Communal grazing and crop residue subsystems are mainly found in semi-arid sub-humid areas. Storage losses are 50% because decomposition of DM is slow (low humidity), but storage practices are poor. Cut and carry, feed from farm and external feed subsystems are mainly found in sub-humid and humid areas. Storage losses are 50%. Storage practices are better, but losses through decomposition are higher due to higher humidity.

> Manure requirements per ha:
> In crop residues and feed from farm sub systems, an extra 200 kg DM is required to compensate for crop residues carried from fields. In cut and carry system an extra 200 kg DM is required because of more intensive crop cultivation.

Nutrient deficient and surplus farms

> Results from studies referred to in "Livestock & the Environment, finding a balance", show livestock units per ha ranging from 2 units (upland Indonesia) to 6 units in irrigated agriculture (three crops per year) in Nepal both under cut and carry sustems.

Based on these estimated TLU/ ha requirements and on the common characteristics of the farms involved it is likely that: In communal grazing subsystems only some former pastoralists may still have enough animals to maintain soil fertility of their cropland, others are manure deficient;
In crop residue subsystems all farms are manure deficient;
In cut and carry subsystems many of the farms with little land may have enough manure, the (almost) landless can build up a manure surplus. This is often locally sold.
In feed from farm subsystems the farms as a whole are manure deficient but internal transfer from pasture / fodder to cropland may result in enough manure to maintain soil fertility of cropland at the cost of declining soil fertility of pastures and field borders.
In external feed subsystems the farms specialised in livestock can build up a nutrient surplus, especially those with little land or with large numbers of livestock. Note: More information on related aspects is presented in degree of crop livestock integration.

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